You still ain't got it ...

To be a "piss-to'l 'smith you have to be a PROFESSIONAL ...

The reason that firing pin stop works is because it's the way John Browning designed it. Unfortunately someone in the Army decided it should be changed. Things haven't been right since.

Anybody have high speed pictures?

There's a lovely discussion by some very smart people on another board with interesting thoughts - including talking about how nice it would be to have pictures - anybody have references to controlled tests with observed distinctions?

Of course as some have said comparing recoil in a 1911 across different shooters can be a waste - Layne Simpson reported trying to do a controlled test of ports and compensators with friction on a Ransom Rest and not getting anyplace.

Bingo! The Black Snowman nailed it square on the hittin' place!

The smaller radius decreases the slide's mechanical advantage in cocking the hammer. The slide is delayed for a fraction of a nanosecond, and bleeds off a good bit of the recoil impetus. The slide moves a little slower and with less force, and softens the blow to the frame... quite a bit, as Ken noted.

Also... Since the slide's delay gives the chamber pressure a tick longer to fall off, the extractor doesn't have to work as hard to break the casing's grip on the chamber walls during primary extraction... and in some instances will actually allow surprisingly reliable function with the extractor removed. Other things contribute to that little trick... but I've seen some pistols that wouldn't quite do it... until the firing pin stop radius was reduced... and it pushed'em over the edge.

The small radius utilizes more of the mainspring's resistance to hammer movement... and allows the use of lighter recoil springs with little or no reduction in frame protection. So there you have it... The original, Browning- designed shock buffer... and it doesn't shred or fall apart every thousand rounds.

Clark made a good point, and spot on. Give 5 people the same gun and ammo, and all will report different recoil impressions. A side-by-side test, like Ken's experience can be revealing though. Even better is to change only the stops in the same gun. The difference is real, and depending on the mainspring and recoil spring load, it can make quite a noticeable difference.

Amazing. This is exactly what Ted Yost is doing to my Delta Elite, to keep the slide from beating the frame to death.

Just amazing what a quality oriented 'smith can come up with to actually solve little issues like this.

I think Ted has headspacing gauges too!

ROFL Snake Eyes! Go to your room!

Shootcraps, you can get the parts from Brownells. I think they're about 18 bucks now, unless you qualify for the discount... then they're 15. There are two types... Original/series 70 design, and Series 80. the one with the -100 prefix is the Series 80, while the -058 is the original or Series 70. I may be confused though... I'll check to verify and report back. If I don't get back with it, the above numbers apply.

Yes. They require fitting. They come with a dead square bottom and you have to cut the radius. They're also over-width and require filing to fit the slide. I do'em with a light press-fit to keep the extractor honest. Fit to the slide without the extractor first and check firing pin operation... Then fit with the extractor in place.

quote:
...but I've seen some pistols that wouldn't quite do it... until the firing pin radius was reduced... and it pushed'em over the edge.

TYPO ALERT! I think you mean "firing pin STOP radius was reduced."

Of course I am perfect in respect to typos ... and only my ego exceeds my good looks ...

Fuff... ya got me! yes... Firing pin STOP radius.

"bleeds off" ? - Can't fool Newton - where does it go?

I can see an energy delta going to heat in squeezing the rear of the slide/slide stop just a tad in a not quite perfectly elastic collision with the hammer - extra energy going to heat and vibration in the mainspring - but it sounds as though less energy is going into the recoil spring - what about conservation of momentum?

Sort of reminds me of the Blish lock - did that actually bleed off recoil to do just a little bit of unnecessary good?

Ah Clark! Picky picky picky! Shoulda gone into a little more detail. The reduced mechanical leverage against the hammer and mainspring is the bleedin' mechanism. The mainspring absorbs the impetus at the beginning... the same way as a heavier than standard recoil spring slows the slide near the end of the recoil stroke...o r maybe that ain't exactly the right way to explain it.

With the current fad of external extractors on 1911 Pattern pistols the firing pin stop does not have the keep the extractor from clocking does this make the fitting any easier? I assume that an non series 80/schwartz safety pistolwould take an OS series 70 stop.

HRT... Not sure which type stop the external extractor-ed pistols with the Shwartz FP safeties use. I haven't been into one yet to see. They keep comin' up with this new-fangled stuff without tellin me, see...

Shamelessly stealing from my betters

Notice that some of the Bulls Eye greats would go the other way and radius the hammer to smooth the action.

quote:
Notice that some of the Bulls Eye greats would go the other way and radius the hammer to smooth the action.

Ummmm... Okay!

Actually, I think that radiused hammer is to limit overcocking and to reduce friction with the slide... but I don't have much truck with bullseye guns, so I really can't be sure on that point.

Jammer noticed pretty much the same thing as Ken did though... Said his old Springer is runnin' smoother with the small radius stop.

On Bullseye guns ...

Sometimes the front of the hammer face was radiused to delay the hammer's backward movement. This in effect gave the slide a running start and was usually used in so-called softball guns combined with light 185 or 200 grain mid-range loads. It also worked well with .22 conversion units. John Browning would have just shook his head, but in some applications it worked very well.

Raises hand

You explained the softer recoil due to the radius of FP, very well and I appreciate it - thanks!

Is this called, or part of what is called Dwell Time?

Quote:
would it be possible for you to post photos of each firing pin stop side by side?

As I'm having some trouble picturing how it looks and how it works, I second that, please-or a drawing, or something. Please and thank you-the 1911 godz will pay you back Tuesday for this hamburger you give me today

I'll try to find a picture, but for the time being look at the firing pin stop in your pistol (or just a firing pin stop) and think of one that is as flat on the bottom as it is on the top. Today's firing pin stops are rounded at the botom when you look at it from the side. What Tuner is talking about is more square and less rounded.

Brownell's pictures are specific not generic

A good EGW picture will show up as #296-000-058

STI picture shows nice contrast as 791-112-045

both of these page 98 in the Brownell's catalog or on line.

Fuff said:
Sometimes the front of the hammer face was radiused to delay the hammer's backward movement.

Yo Fuff! Clark shot me a PM and described the mod. Once he mentioned Behlert, I knew what he meant. I had it in my mind that it was the angled face that Ken Hallock used to do. I recently did a slight modification on a hammer and a FP stop... gave it a larger radius... on a softball gun that I fixed up for Kelie. The 5-inch gun cycles smartly with 185 grain SWCs loaded to 600 fps Feels like a 9mm. Now, if I could just save some of the ammo for her...

Actually it was Austin who first showed me the trick. If you are building a specialized bullseye match pistol using powderpuff loads this is the way too go. This is particularly so with heavy (ribbed) or long slide pistols. Service pistols and hardball guns are entirely different. What we have here is a "tools vs. toys" issue. Both methods are correct when used for a particular purpose.

When the slide recoils the firing pin stop presses against the hammer face and cams the hammer backwards. Depending on how much the stop is radiused on the bottom, and the shape of the hammer face, the resistance the hammer presents to being rotated will be relatively light (good for some kinds of match guns) or heavy (good for service pistols or other firing heavy ball loads). During the slide's cycle the hammer (which is under spring tension) works as a brake along with the recoil spring to slow the slide's velocity. Where the recoil spring is most effective at the end of the travel the hammer does its thing at the begining. This is important because within micro-seconds you want to keep the slide and barrel locked together until the bullet has exited and breech pressure dropped. After that the recoil spring's main job is to return the slide to battery. Too many people try to control recoil by installing extra-heavy recoil springs. This is often a mistake if the pistol is correctly set up the way Browning intended, and as Tuner has explained. The EGW firing pin stop comes with no radius on the bottom so the 'smith can shape it for whatever he has in mind. In the matter under discussion this is important because it is the only stop on the market that isn't over-radiused in the first place.

The attached is a picture of an EGW firing pin stop. On the left you see it as it comes from the manufacturer. On the right you see the small radius that Tuner has explained. I'll leave it to him if someone wants more details. Clearly this man knows what he's doing. I would observe that the modification may make it harder to pull the slide back by hand (which is why the Army made a change to the current configuration with a larger radius) but making the slide harder to move rearward is the whole idea.

Quote:
Riley...The standard stop has a 7/32nd inch radius. The original... like Ken has... was/is .075-.080 inch, with .078 bein' print spec.

You and I have talked about me doing this to one of my guns before but I haven't gotten around to it yet. I will try and order a FP stop but I had a question as to how to accurately measure that .078" radius.

Also, are you sure about the new standard being 7/32? That's a big jump from .078" to .21" it seems.

The way to accurately measure it is with a radius gauge... but a good set is pricey, and it's not imperative that it's precise. Use a 5/64ths inch drill rod to estimate it. The radius of the rod... half the diameter... is just about right. Just hold the rod up to the bottom corner to see about what the radius should be and duplicate it as close as you can. It's important that the cut is kept even and straight across though. If it's not, it'll cause a side load on the hammer pin. This is more important than the radius being precisely .078 inch. Since I cut mine freehand, I doubt if any of'em is exactly on the mark.

EDITED TO CORRECT DRILL ROD SIZE! Use a 5/64ths rod to estimate the radius by aligning the edges of the rod with the corner. Sorry... hasty instruction make for bad results.

IANAP! (I am not a pistolsmith). And Tuner has forgotten more about 1911's than I ever even hope to know.

BUT.

I don't think that the differences here would be reliably perceptible by any normal human being. I think this is probably a false perception. Something I think that even the venerable Tuner might fall prey to from time to time.

The only way to know is to run double blind tests.

Can Tuner or some other advocate do this? I am sure you know how.

Lacking a double blind test, I call BS. It just "don't seem reasonable". Sorta like wine tastings -- with the blindfolds off, everyone is sure that the $200 bottle of wine if far superior to the $10 bottle. With the blindfolds on, no body can reliably spot which is which.

Thank you for the photo, Fuff. It looks like what Tuner recommends is juuusst a leeeetle more than breaking the edge of the firing pin stop. It looks quite a bit different than the fps on my Springer, which has a more pronounced rounded radius.

Sorry guys... I put in the wrong drill rod size in my response to Tarpley. See the edited text.

As an alternate method the EGW stop can be beveled lightly to just break the corner and stoned to blend it into a more rounded shape. I prefer the full radius, but either will work.

The egg asked:
The only way to know is to run double blind tests.

Sure. Just cut one with the radius and use a standard stop in the same pistol. Yes... I've done it. Yes... there is a difference in felt recoil and muzzle flip. Another test is to use a shock buff and see how much longer they last with the small-radius stop. Again, the difference is the result of the mainspring absorbing a little of the slide's energy and delaying it for just a fraction of a nanosecond before the slide gets moving. Thus it "bleeds off" a little of the recoil energy in the beginning of the cycle, rather than depending on the recoil spring alone to handle it. Simple physics. If the mechanical advantage used to compress the mainspring is reduced, the slide has to work harder to overcome the spring's resistance to compression, and that takes time. Time to let the chamber pressure drop... Time to get the slide moving at full speed... Time to cock the hammer against the mainspring. The delay is very short, but things happen fast inside the chamber and barrel. Once the hammer is cocked, the influence of the stop is over... but its mission has been accomplished and the slide moves a little slower as a result. Lower slide speed means less shock when it hits the frame. Less shock means less felt recoil.

I thought that was a little too much radius at 5/32".

For what it's worth,the radius on my Officers ACP is 11/64"(the only one out of the safe to check),so 5/32" wouldn't be much improvment.

I was thinkin' in half diameters there. Gotta slow down and stop tryin' to eat while I do this!

Hey Tuner, what you are describing is not double blind -- maybe you did it, but just have not described it, here.

I just wish we were closer together, we could set up a test in short order to prove this thing one way or another. Basically, neither the shooter nor the person administering the test can be allowed to know which gun is which. Then, in a random manner, the shooter(s) fire the weapons and try to identify which is which. Enough rounds must be conducted to allow enough guesses to be made to determine if there is a statistically valid pattern (can you really tell which is which, no foolin'?), or if it is just guessing (which would be my guess!).

And I would even be willing to wager a shilling or two on the outcome!

I wouldn't think it would be that hard to check measurable recoil with a recording gauge attached to the trigger guard with a Ransom Rest.

But felt recoil is another matter, as it varies from person to person.

You would have to use the same gun and ammo,with the only difference being the firing pin stop to really be scientific about it though.

At one time the Old Fuff conducted some experiments with a Colt equipped with a .22 conversion kit. The main problem with these kits was that the slide was too heavy for the little rimfire cartridge to move. There was a marked difference if the firing pin stop was fully radiused across the bottom, and it and the hammer face were highly polished. The intention here was to reduce the effect of the hammer (and its spring) acting as a brake, which is the opposite effect that you'd want on a service pistol firing ball loads or hotter.

While some may find a difference in felt recoil, that isn't and wasn't what I was interested in. Better reliability and less battering of the frame and slide was, and still is.

As a side note: Browning's earlier pistols, and the blow-back .25, .32 and .380 pocket pistols all have a small radius engagement in the slide where it contacts the hammer face. This feature that Tuner has pointed out was a standard procedure with Browning, and not limited to the 1911 design.

The feel of the recoil is all I am interested in. If it feels less,it must be less.

I didn't intend to test anything when I went to the range. I thought the Norinco recoiled less from earlier firings but had never shot the two of them together.

At this time ,I did shoot both of them together and proved to myself that the firing pin stop did make a difference.

I suggest that if you have any doubts,that you make your own tests.

I am happy with my results and do intend to put the same stops in all my 1911's

the rest of the story?

Just curious... does anyone know why the Army dictated the radius change to the original Browning firing pin stop design? Seems to me that the larger radius might improve reliability under battlefield conditions...might also increase service life by reducing forces on the hammer/pin... all at the expense of sight recovery and general shootability. I guess if one had to choose between reliability and about anything else under the most adverse conditions imaginable then reliability would win! For me, any improvement in shootability would be appreciated more, however, as a fairly heavy lead user I'd still be concerned about service life... if that's an issue here at all.

bullseyeboy asked:
Just curious... does anyone know why the Army dictated the radius change to the original Browning firing pin stop design?

It was done to make the gun easier to hand-cycle with the hammer down.

The biggest majority of the soldiers who were authorized to carry the pistol were restricted to Condition 3 carry... Magazine loaded, hammer down on an empty chamber... which required that the slide be cycled to ready the gun or action. Some of the lads complained that it hard to do in a hurry, and the Ordnance Department went back to the drawing board.

Rumor has it that several of the custom smiths who build the gun in 10mm have found that the original radius on the stop allows the gun to be used with 18- 20 pound recoil springs rather than the more common 22-24 pounders... with no loss in frame protection. Seems like I also heard that the final recoil spring rate was determined by the mainspring rate. I may not correct on this point, but it does make sense.

There's also a "clew" there for the folks who lighten the mainspring load in order to lighten the trigger action... without compensating for the reduced braking effect of the lighter mainspring.

Think about it...

I agree with Tuner again. (I would have had the answer, but his keyboard is faster ... )

The Army had experimented with Browning designed/Colt .38 automatics, and then a whole bunch of .45 prototypes. All were carried in full-flap holsters, and quick draws weren't on the program. Before a change was made on the firing pin stop some would draw the pistol (slowly), cock the hammer, and then cycle the slide. Of course someone complained, and the change followed.

It has been wisely said that when you change or modify something in this pistol at least two or three other parts and/or they're function will be affected. Unlike most handguns it was not designed - it was developed over a period of five years (twice that if you count the earlier .38 pistols) and as defects or problems were discovered they were corrected in the next prototypes. After the design was finalized in 1910 and adopted in 1911 few additional changes were made during the whole time it was used by the military services, and today's commercial guns are little different then the first guns except for cosmetics and materials.

Quote:
It was done to make the gun easier to hand-cycle with the hammer down.

BINGO!

Which is also the best way to test and prove the theorum.

Try it yourself and you will be able to FEEL the difference in the force needed to retract the slide with the hammer down.

BluesBear said:
Try it yourself and you will be able to FEEL the difference in the force needed to retract the slide with the hammer down.

Exactly so... and you'll notice that the extra resistance is at the very beginning of the cycle.

The mechanics are very simple. The slide isn't driven through its full travel... only during the first 1/10th inch of movement. There is a set level of energy produced when the gun fires... and that energy is established in the time during the first .100 or so inch of slide travel. Once established, only momentum completes the cycle.

The small-radiused stop... due to a lower point of contact and reduced leverage (mechanical advantage) against the hammer... causes more of that limited amount of energy to be used in moving the hammer, and it does most of that during the onset of hammer rotation... or in the first 1/10th inch of travel.

Since the hammer also has mass, its inertial resistance to movement is also figured in... and like any other object... once motion is established, momentum helps to keep it moving... BUT... the slide still has to work to start the process.

To simplify it... the slide has to work to accelerate it from a dead standstill, and some of the energy is dissipated in getting the hammer to move.

The more energy it takes to get the process started, the less momentum available to keep the slide moving... hence the reduced impact and felt recoil when the slide hits the stop surface in the frame.

Other factors must also be considered. Mainspring load... Hammer mass/weight... Even friction... but if all else is equal, the slide's speed and momentum will be reduced after the hammer is cocked.

Well, I bow out.

It seems I am heavily outnumbered by the "my subjective perception is reality" crowd.

Can't really argue with that. Nor do I want to.

Ya'll have fun now!!

Reduced Recoil?

I would say the reduced radius FP stop has the effect of slowing the slide down a "tad" due to the lack of mechanical advantage against the hammer and mainspring. This retards the shooter's impression of the whack that happens in a normal fitted out pistole when the slide hits the end of its travel. The whack is still there, it's just not as ABRUPT and it's partially taken up by the mainspring.

Sometimes the forest gets missed because of too many trees …

The original Browning-designed firing pin stop was intended to reduce battering between the slide and frame to insure greater longevity in the operational life of the pistol, and to better control the timing of the slide's cycle to increase reliability. Tuner's experiments and observations contained in an earlier post showed this is the case. (If plastic recoil spring buffers last substantially longer something is going on).

A side effect of using the small-radius firing pin stop is less felt recoil. This is subjective on the part of different individuals, but Ken is obviously sold. Others may or may not be, but it would seem likely that if the slide comes to a "softer stop" at the rear end of its travel the felt shock would be less. If one is using a pistol with a lighter slide (read that "sub-compact") the effect might be more noticeable. In any case the mechanical principals are one thing, and subjective issues concerning felt recoil are another.

This thread has been, and continues to be especially valuable because it brings to light something that few 1911-pattern pistol owners know about, and for that we can thank both Ken and Tuner. One may, or may not decide to try a different firing pin stop, but for around $20.00 it offers an interesting option, and it is far more likely to be helpful then many other more expensive gadgets and gimmicks being sold as aftermarket accessories.

As part of my "Master Plan" (tm) for my Delta Elite my latest update has been going from the stock FP stop to the EGW peice, fitted, with NO radius. This was after going to a convetional 20 lbs recoil spring, a standard steel guide rod, and a 25# hammer spring to try to get the recoil impulse to be more comfortable.

I'm also intentionally leaving the heavy stock hammer in place in the hopes that it's extra mass will assist in extending the unlocking time as well. I can't find anyone who carries an extra heavy version. People seem to be obssessed with their lock times and cycle time when it comes to aftermarket hammers

Changing the slide stop made more of a differance to me than raising the hammer spring pressure 2 lbs and I can shoot the gun accuractly with noticably shorter split times.

However, I'm still getting an occasional FTExtract. Particularly with my full power 135 gr loads when the gun is dirty. Perhaps I need to look at the chamber condition and I know I still need to check the extractor tension. Every 25-50 rounds one will just stay in the chamber. But I'm not going to hijack this thread with my problems, I already know where to look to narrow them down

Black Snowman...Don't leave the corner sharp. If you want minimum leverage, just lightly break it on a narrow bevel. Your hammer will thank you.
*****************

Close BigG...but it's not a perception. It really does soften the blow.
*****************

Egg! We're not tryin' to shout ya down. We're tryin to eddy-cate ya.

While I completely agree that felt recoil is subjective and varies from one person to another, there is a provable, mechanical reason that the recoil is reduced. Why is it reality and not a subjective perception? Because a mechanical change has been made that reduces the available force necessary to propel the slide to full travel. More force required to cock the hammer means less momentum remaining AFTER the hammer has been cocked.

Less momentum means that the slide is moving slower. Less slide speed means less impact energy when it hits the frame. Simple physics.

Let's try an imaginary experiment and see if it makes more sense.

Fact: The reduced mechanical advantage in cocking the hammer requires more of the slide's momentum to perform that function. Simple machine... The closer to the fulcrum (the hammer pin) that you put the force (the recoil momentum transmitted via the slide) to the load (the hammer's mass and the mainspring's resistance to compression) the less total force is available to complete the cycle once the extra resistance has been overcome.

You, plus a theoretical friend and a basketball decide to put it to the test.

Your friend holds the ball between his hands in front of him at arm's length with just enough force to keep the ball from falling.

You punch the ball with a hard right cross of say... 200 pounds feet of energy... and knock it into his chest. Assuming that the ball's mass and inertial resistance and the friction imposed by his hands absorbed 10% of the energy... the ball strikes his chest with some 180 pounds feet of force.

In part two, your friend holds the ball again, but this time he presses inward on the sides of the ball with all the strength that he has. You punch the ball with a theoretically identical right cross... 200 foot pounds again. The force that your friend is exerting on the ball requires more of the available energy to dislodge from his hands and send into his chest, but the force of your punch is the same.

Everything remains the same except the frictional resistance to the ball's acceleration imposed by the force that he exerts on the ball. Agreed?

Your punch is the recoil impetus. The ball is the slide. His chest is the frame's impact surface. His hand pressure is the difference between the two FP stops, and is thus the only thing that changes the ball's resistance to acceleration.

In which experiment is your friend's chest going to take a harder impact from the ball? Do you think that it's only his perception of less impact when he tightens his grip on the ball... or is it reality? After the punch... Will the ball move toward his chest at the same speed in each case... or will it be slower when he grips the ball tighter?

Do you reasonably expect that the ball's impact against his chest would be the same in each scenario... or do you expect that it would be reduced with a tighter grip on the ball?

You have missed my point completely (I think!). My point is that it will be impossible for a human being to be able to perceive the difference in forces you are discussing during the act of firing a 1911 .45 acp pistol. Any one that claims to be able to do so is, in my opinion, deluding themselves. I have suggested a method to prove this one way or another.

However, OF COURSE changes in the design or specifications of things like the firing pin stop, and indeed any of the elements of the machine, will influence the operation of said machine in some way. I am not disputing that at all -- it would be silly to do so. I am focusing in on the fact that the changes you are discussing in this particular thread can't be detected by a human being -- they are too small for the human sensorium to sort out!

And with that, I really am out of here. The weekend is almost upon us, and I have some shootin' to do.

Oh, and by the way Tuner, it has been proven conclusively by better men than you, that I am uneducable.

the Egg insists that:
The changes you are discussing in this particular thread can't be detected by a human being -- they are too small for the human sensorium to sort

Nope...t hey are detectable, and you don't have to go to the trouble if fitting a firing pin stop to feel it. Just get one 21-pound and one 25-pound mainspring and swap'em back and forth. Use a fresh shock buffer with each mainspring to begin the test and see which one shreds first.

The difference between the two stops is about the same as the difference between a 14 and an 18 pound recoil spring... or the two above mentioned mainsprings. It really is that much. I'll conduct the test... but it'll hafta wait for a better time. Got way too many pinto beans on my plate right now.

And... the only man that I ever met that couldn't be educated was my brother- in-law.

I don't guess that I am a human being. The first time I fired the Norinco after Tuner installed the stop, I noticed the difference in the recoil feel. I fired it several times afterwards and always felt the same.

This week when I fired it along with my Colt of the same size,I could really tell the difference in feel.

Same ammo, same size pistol,s ame springs and same day. I didn't mention the fact that a friend was with me and fired both as well and he had the same feel as I did.

No matter who is right or wrong as long as I like the feeling that I get, I am happy.

Egg, dunno about a double blind test, but I do know for certain that a small radius firing pin stop was part of the solution to correct some timing/reliability issues in a Colt Officers Model.

That isnt a subjective opinion. Before the EGW firing pin stop was installed, the pistola wasn't reliable. After installation of the EGW part, it is reliable.

I'll take your advice 'Tuner. I'm refinishing the gun tomarrow so I've got it all apart anyway. Only excuse I have is I can't seem to find what I did with my stones . . . [shuffles feet through piles of junk on the floor while looking about]

Loose brick... aka Field Expedient Abrasive Tool... but if you're not too far from a hardware store, a sheet of 320-grit wet or dry paper on a piece of glass will do. Hold the corner on a 45 degree angle and pull it sideways across the paper evenly to break the corner straight across.

Saltydog mah fren! Good to hear that little beastie is still doin' ya right.

The FP stop was just a small part of the timing puzzle. Believe it or not,

I've got another OM that's more stubborn than yours was! I finally squashed all the bugs on the 3rd try. It's runnin' and ready to go home now.

Ken buddy! You and your range pal ain't the only ones to notice that little side benefit. I did one up for a guy a while back without tellin' him about it, since I had to fit an oversized stop to keep the extractor from clockin', I figured... "Why not"? When he called me to report on the test-fire session, he remarked about how his new lot of ammo must be "weak", since the gun wasn't as bouncy as it was with the old lot. Sellier & Bellot hardball, I think it was.

Well, I am early to the party, but late to this thread. Not sure where I first picked up on the advantages of the EGW fps, but I am sure it was reading about different people's experiences with their Delta Elite's. Anyway, I ordered one, and had the good sense to follow Tuner's advice about breaking the edge. This was a used gun, but I estimate the mainspring to be about 25 pounds, definitely longer and stronger than stock. The previous owner's recoil spring was probably 28 pounds! Way too much!

Sidebar; Tuner, have you ever seen a change in recoil spring cause a change in point of impact? Like 4" at 25 yards?

To make a long story short, minor modifications will probably cause less problems than major modifications. The combination of a slightly heavier mainspring, a slightly heavier recoil spring, and a slightly less radiused firing pin stop all add up to a 10mm which shoots much better. If Colt had done this the first time around, I bet that the Delta Elite would still be in production. Of course, that tungsten recoil spring plug is just icing on the cake.

Yes, it is hard to rack the slide with the hammer down. No problem, simply cock the hammer first.

Unless they've sold out of'em in the last two weeks, the Series 80 type stops will work in either design. PN 296-100-001. Price is the same.

Call Practical Shooting Supplies at (800) 554-3230. They have them in stock. Mine was $14.00 shipped.

http://www.practicalshooting.com

I wanted to bump this for those interested.

I got my FPS in a while back and had time today to fit it. Took about an hour to file down the sides (same amount off of each side based on the previous stop). I made it a tad tighter than the old one. I rounded the radius using a 5/32" drill bit as a guide like Tuner said then polished off with 320 and 600 sandpaper making sure that the shoulder stayed even all the way across. Reblued using cold blue and installed in gun. Function tested fine and wasn't nearly as difficult to rack the slide as I had been led to believe. Took it to the range and test fired with no issues. I cannot really tell if the recoil is reduced or not. Won't really know till I get on a clock with it.

You may not have noticed much difference if you're using a lighter than standard mainspring. That's part of the whole enchilada, and it doesn't really start showing up until the mainspring load gets up above 21 pounds.

I am using a standard mainspring... whatever that # might be. I toyed with the idea of lightening it but I didn't based on your recommendation a while back. On a side note though, I have really got this gun tweaked out now and I LOVE shooting it now.

How much does the firing pin stop modification increase recycle time? Is the increase in time offset by greater control? I know this is picky, just wonderin'.

Well, I can detect no perceivable delay over what I had. I CAN tell you that during double-tap drills yesterday, it seemed like I was back on target a tad faster than before. 'course that could be because that was what I was expecting. Like I said, I really won't know if this is a definite improvement until I get on the clock at the next match.

You won't have any perception of a delay. The difference is what you noticed. Since a little more of the slide's momentum is absorbed at the beginning by the mainspring, it doesn't hit the frame as hard... and the muzzle flip is reduced when it does hit. The stronger the mainspring, the more difference you'll notice. Standard is 23 pounds. It's a different "feel" than just using a stiffer recoil spring to soften the impact, since the recoil psring tends to push against you as the slide moves. The small radius/stiff mainspring soaks it up right at the beginning and over just a tiny amount of slide travel. Once the hammer is cocked, its effect is over... except that the slide's speed and momentum is reduced before the recoil spring really has an effect.

Interesting dynamics when really study the whole effect... and more noticeable when you swap FP stops and try'em back-to-back.

I looked at my SA milspec and it already had that done to the firing pin stop I guess I don't have to do it myself.

Your Springer's stop has the 7/32nd inch radius at the bottom. The one we're using is the EGW square-bottomed stop with a smaller .078-inch (nominal) radius that has to be hand-cut, and was the standard radius in the original design before the Army asked for the one like yours. It was requested in order to make the pistol easier to hand-cycle with the hammer down.

I'll post a pic tomorrow when I can upload from the camera so you can see what we're talking about.

Okay, here is a somewhat blurry pic of what the before and after looks like. The FPS in the foreground is the one that came on my Kimber (current design) and the one in the background is the original JMB design.

edit to add: I think I have discovered the error... 5/32" is .16" and 5/64" is .08". I think I was supposed to use a 5/64" bit.

edit again: 'Tuner, I see you corrected the spec for the drill bit. Cool, I was going to suggest that you do. I had originally questioned how we got to .078" using a 5/32" anyway. Now I know what happened. I will leave it as is... seems to be a good compromise.

FOR THOSE OF YOU WANTING TO DO THIS, MAKE SURE YOU USE A 5/64" BIT.

5/64 = .078

Which one?

It's the 5/64ths bit... My apologies Greg. I had my head screwed on backward that day... and made the same mistake here on the thread. I was thinkin' in half diameters and didn't catch it before gamachinist did.

Your radius will slow things down quite a bit... just not as much as the .078 radius will. I'm gonna call Brownells today and order a few things. I'll have'em toss in a new EGW stop and send it... or... if they're still out of stock on the pre-80 Series type, you can order one from EGW and I'll pay for it in exchange for the stop you have pictured. I can always find a use for it. let me know how you want to do it.

Again... My apologies to all for my brainfart on this project.

No problem... I'll keep the one I have for now. It seems to shoot really well now. I may tinker with another one later on.

After reading this thread yesterday I went home planning on working on the FPS on both of my 1911s, but when I looked at them they both have the FPS like the blurry one in TarpleyG's picture. One is a Kimber TLE II and the other is a Springfield Mil Spec.

So the question is am I already getting the lower felt recoil or should I replace the FPS with one modified like 1911Tuner suggests?

Tallgrass... You'll get the reduction over the now standard stop... but it won't provide quite as much difference as the .078 radius. Looks like somebody caught on to the return to original mindset... thought that the .078 radius looked a bit too brutal... and split the difference. Interesting.

FWIW... One of the top guns in the custom industry tinkered around with that radius in a 10mm pistol and found that he could get the same frame protection with the EGW stop and an 18 pound recoil spring as with the 7/32nd radius and a 22-pound recoil spring... with reduced muzzle flip to boot. IIRC, it was Ned Christiansen... but I may be mistaken on that, so don't hold me to it.

You have to but a new firing pin stop. A company called EGW makes one that is both oversized and that has a square corner where that radius is. You have to first fit it into the channel like a normal FPS then you have to radius the bottom edge to a 5/64" (.078") corner.

Go back and reread the thread and you'll understand better what is going on.

Shoot me a PM when they get in and I'll let you know where to send it. Unless, of course, you still have my address from before.

I have made no scientific measurements. My Delta Elite with an 18 pound recoil spring, and an unknown, but definitely 23+ mainspring, (probably 25, it came with the gun), plus the small radius firing pin stop, flings ejected brass about 2 feet further than a stock Gov't model firing factory hardball.

This is with a heavy load of Power Pistol, and 180 grain bullets.

If Colt had used this setup, I think that they would still be manufacturing Delta Elites.

No voo-doo, no black magic. Just simple physics in action.

Before the addition of the small radius fring pin stop, the same loads in that gun would send brass halfway into the next county, even with a 20 pound spring.

I am sold on the concept. I am thinking about using the reverse side of that concept in a 9mm Gov't model. Works both ways.

Any available in stainless? OTOH, I've had a blue extractor in my electroless nickel Colt for years until I found one in stainless and it never bothered me. I'm not running out and replacing any on a working gun, but I'll also replace the slide stop with one of these EGW ones next time an extractor breaks as the quality of extractors seems suspect these days.

Good thread. Someone should send this to Kel-Tec, I bet this is the basic problem with the P3AT extraction issues -- too rounded at the bottom of the slide to make up for the heavy recoil springs on the little gun.

The part is machined from Oversize A2 stock, No MIM need apply!

45 to 49 RC. We have sold about 12,000 so not so much a secret

They should be selling for 15.00 retail. But if you act now, and check out our new shopping cart and mention in the note field that you saw offer #323 on the LTW forum we will sell you a stop for 13.00 plus shipping. and if you act now well throw in a shock buff

As to verification that it works.

First case study from Larry Stuerwald that was the gunsmith for Para for several years. He was having problems with P-10's leaving rounds in the chamber. We put a square corner stop in and it worked fine, took it back out and it started leaving cases in again.

Gary Heindman from Ace custom 45 uses it with his 45 super, he said because of the stop he was able to drop 4# in his recoil spring.

Very recently a customer was having problems with a very short Kimber with the same results, std stop and it would leave rounds in the chamber (external extractor gun) with the stop it slowed things enough that the gun funtioned fine.

Funny that you guys mentioned Austin, it just so happens I worked there for 4 years in the late 80's, and yes if raising the contact point on the hammer allows a light load gun to funtion it stands to reason lowering the contact on the hammer would do the opposite.

EGW and George Smith

Ladies and laddies... I give you Mr. Evolution Gun Works himself.

Howdy George! Welcome aboard.

I ordered 5 of those stops from you a few weeks ago, when Brownells kept tellin' me that they were out of stock. I don't know if it was you that I talked to or not, since I didn't ask and the guy I talked to didn't give a name... but he told me that anything that Brownells carried from EGW, I could order direct. I'll probably order a few more next week, since I made the mistake of doin' a few for the guys down at the range... and suddenly I've been swamped with requests for more.

The general reaction... besides the obvious... was: "What a great idea! Why didn't somebody think of that before??!!" When I told'em that somebody had thought of it over 90 years ago, they were flabbergasted and mystified. To date, I've installed over 30 for for the PHA club members alone... with requests for 7 more as soon as I get settled in the new house.

As a side note... I've got an early 40s production High Power on loan here... complete with internal extractor and... you guessed it... a small radiused firing pin stop. 'Magine dat!

This is an prime example of how this site has so much useful information that is shared amongst its members.

I have a question for everyone.

What if the FP stop is not beveled at all? Would the slide be too difficult to retract?

Would this cause some type of malfunction or does it need to have, at the minimum, the 5/64th bevel?

Why not try it and you tell us?

Quote:
Don't leave the corner sharp. If you want minimum leverage, just lightly break it on a narrow bevel. Your hammer will thank you.

Nothing else is quite like pounding on a sharp edge for stress cracks.

But did we ever figure out if the Kimber wants a Series 70 or 80 FP stop plate?

I'm glad this thread resurfaced. Today I was looking at a couple 1918's (or were they 1917?) that have not yet been sucked into the void of no return in Tuner's basement. The "original" 1918 USGI has a small radius firing pin stop. The 1918 USGI Augusta Arsenal redo has the "modern" larger rediused stop.

I've shot both types of stop in modern 1911's. The recoil seems less with the smaller radius stop and it is quicker to return to target. It works for me. Thanks Tuner.

And thanks George! Your product is a welcome improvement. Welcome to our little pastime!

I'm new to this group. I've been lurking for a while and would like to add a suggestion. The pistol is different, but the concept is similar.

I have an officers ACP .45 that when the hammer was down had a small amount of play in the hammer. The hammer was not under tension. This gave the slide a running start before beginning to compress the main spring. Recoil was brisk. I installed a longer hammer strut from Cylinder & Slide Shop (via Brownell's) which placed the hammer in tension all the time. It made a slight improvement in felt recoil. I expect the same thing would help a 10mm. Even if there is no detectable looseness in the hammer, the increased tension would probably further delay unlocking.

Apologize for the user name. All the good ones were taken. Just ran a finger across the keyboard.

You have a point. We usually start with the perception that the pistol has been correctly put together in the first place, at least until informed otherwise. Today too many firearms leave the factory without adequate inspection, and this is something we shouldn?t forget.

Floppy hammer

I run into the same deal once in a while. It's usually a spec issue or tolerances stacking up in the wrong direction. My fix involves facing a few thou off the top of the mainspring cap to let it sit a little higher in the housing. A quick-fix is just to remove the cap retaining pin and let the cap ride fully up against the end of the strut.

Kimber takes what?

I was curious about this myself from the start of this thread... Never thought that it would go this long and still not have an answer.

Good news. I just called EGW and talked with Jeff. Great guy and very knowledgeable. According to Jeff, Kimber owners can safely order a Series 80 stop for the Kimber series II in .45. If you have a series I or pre-series designation than a series 70 stop should be used.

I should also note that Jeff did say that a series 80 stop should work in most all 1911's out there. (I think early on Tuner said this as well)

It helps if it is correct... but I have my doubts. A Series I Kimber and a Series II Kimber, unlike a Series 70 and 80 Colt have no difference at all at the extractor or FP stop plate. You can use either a Series 70 or 80 extractor in either a pre-Series II or a Series II Kimber. So, why would a Series II take something different than a pre-Series II? I'm of the opinion that either will work in either model.

He compared the Series 70 Colt to a Series I Kimber and a Series 80 to a Series II Kimber. He did also mention that the Series 80 would work in most all guns out there.

If there is no difference in the slides of either model, I dont know why either. Just figured that I would make the call and ask so that I could get some on order as well. Just posted what I was told. I dont have a Series I to take apart and measure. As has been noted before, they are really nice people over there - If you dont mind to make the call and clarify. Just be sure to post what you learn.

edited to add...

 Quote from Kruzr here: http://thehighroad.org/showthread.ph...&highlight=egw
 
 Kimbers (all of 'em that have them) take Series 70 type internal extractors. If there is a difference between a Series 70 and 80 FP stop (?), then you want a Series 70 for the Kimber.
 
 The reason you need a Series 70 type grip safety for a Series II Kimber is 
the thickness of the arm. A Series 80 type has a thinner arm that won't engage 
the push rod for the FP block. The Swartz safety is not like the Series 80. 

And that kinda nullifies your last post about there be no difference at the extractor or the FP stop from your own post. If I knew from personal experience I would have posted on that. I will take the info from EGW and run with it.

Did I miss something?

I see no contradictions in Krusr's posts.

In Colt guns there is a difference between a Series-80 and pre Series-80 firing pins. You can use a Series-80 firing pin in a pre Series-80 gun but not vice-versa.

As has been stated before the Kimber and Colt safties work differently.

Quote:
He compared the Series 70 Colt to a Series I Kimber and a Series 80 to a Series II Kimber.

That explains his misunderstanding.

Quote:
And that kinda nullifies your last post about there be no difference at the extractor or the FP stop from your own post. If I knew from personal experience I would have posted on that. I will take the info from EGW and run with it.

Where did it nullify anything? Was there something I did to offend you? I can't seem to find it.

Run with whatever you want, apparently either will work (and take it easy on the coffee.)

I have a question about fitting the stop. It is oversized, but how? Is it thicker, so that all you have to do is sand down the back of it to fit it???

Many stops are slightly thicker and need to be slightly thinned.

But there's often more than that.

Most stops also need to be fitted to clear the ejector. For example Commander and .38 Super/9mm models have a differently sized ejector than the one used in the standard .45 Government model.

The Series 80 firing pin stop is cut for the Series 80 lever on the right side and on the left for a Commander ejector.

This will fit any gun we know of. Govt commander officers, 9 38s 40 10 and 45.

The Series 70 FP stop has no cut out on the right for the Series 80 (hence the Series 70 discription) On the left side it is cut for a 5" .45 ejector. The GI ejector.

As soon as you leave the 5" gun the ejector changes in almost all gun. (SIG's smaller guns will probably use the .45 full size ejector)

So if you have a Series 70 Commander in .45 the ejector will hit the FP stop. same for any just about every short gun, Commander or Officers model.

IF you file out the path for the ejector you will most likely leave a square inside corner and as a commander it will be closer to the firing pin hole and crack through faster than you will like. The stops are both made with a corner radiused endmill to leave a .020 radius in the inside square corner on either side. If one fails we will replace it free, provided you did not file the radius out.

Kimber's series 2 safety is different from the Colt/Para ser 80 cut out. if you have a 5" kimber you can use a ser 70 45 stop.

Fitting

We made the stop to the widest slide cut out I have ever measured.

.482 you will almost always have to fit it side to side. if you do it by hand take a little at a time and check yourself with a caliper, hold it up to the light and see that you are strait and even, do one side and finish than the other, equil amounts.

They are .100 +/.0005 -.001 and you will have to remove stock from the stop or open the cut out in the extractor for it to fit some times.

This gage is what we use to check the slide size, you can than install the extractor and see how wide you want to be. http://egw-guns.com/catalog/product_...products_id=63

Sorry for any confusion we may have caused

George said:
...Do it by hand take a little at a time and check yourself with a caliper, hold it up to the light and see that you are straight and even, do one side and finish than the other, equal amounts...

This is easier to do by laying the file down and pulling the side of the stop lengthwise on the file, instead of clamping the stop and trying to control the file. It provides more control if you can arrange to have the file roughly at eye level, and draw the stop toward you.

Also... Once in a while, you'll find a slide that the stop is a little too thick to fit into. Rare, but it does happen. Thin the stop from the forward side... (As oriented in the gun)... and cut by drawing the stop on the file. Remember to break the sharp edge around the hole lightly with a countersink or a tapered stone to prevent a stress riser/crack from forming, and to give the butt-end of the firing pin a smoother path.

George... I'll probably call tomorrow. The last 5 that I ordered have been spoken for, and I need a few more.

Is "The Function of a 1911 - Part II" available yet? I don't know where I got Part I, so I cannot refer. I'd sure like to make "Part II" required reading also!

This thread has been a real thought provoking, eye-opener for me!

I read thru this thread about a week ago and had one of thos "light bulb" moments. I bought a Hi-Power a few months ago and immediately pulled out the 32lb hammer spring and replaced it with a 26lb spring. I also put an Olympic Arms 1 in 16 twist barrel in it cause all I shoot is cast. Long story short after about 100-120 rounds without cleaning the gun gets a little difficult to go into battery. This is due to bullet lube and crud gunking up the little recess in the breech face where the hood locater pin "thingy" goes. After reading this thread I thought just maybe I'm the cause of all this crud because the gun is opening a little too soon blowing the lube back into the slide. I put the 32lb spring back in and now over 200 rounds later with no cleaning everthing is running fine. The good thing about it was since I had polished the sear and hammer the 32 lb spring only added about 1/2 lb to the trigger pull. Thanks for a great thread! Nick

I did it!

Finally had time to sit down and try this out. Removed the fps from my Springfield V10 Ultra and started fitting the new one. I noticed that the original fps was strongly beveled. Compared the two so I wouldn't screw things up too much.

The main point was its width. Trimmed some off the left side and it finally slid all the way into place, with the firing pin hole lining up just right. Then I had to raise the shoulder a bit to clear the ejector. Broke the bottom edge to give it just a bit of bevel and things looked pretty good.

Took it to the range this morning. Boy, there seems to be a noticeable difference! For such a small gun, it barely moves. I know the ports help, but don't remember it being so smooth. Ran a few magazines through it, stopping after each to check for unusual wear and found none. After a bit I noticed two, equal marks on the hammer below the marks from the original fps. Looks like it's hitting nice and even. I"ll have to try it some more next weekend. If that looks good...

Have ya noticed any difference in your ejection patterns? The first thing that many people notice is that the brass hits the ground from 25 to 50% closer to the gun than with the bad old stop...

Now... Ya wanna really feel "smooth"? Drop your recoil spring down 2 pounds and try it. Except for the extreme-duty beaters, I use 14 pound springs in all my 5-inch guns. Smoooooooooth!

Thanks Tuner. I was at an indoor lane and the empties were bouncing off the side wall, so I don't know where they would have landed.

I'll order a 22 pound spring from Wolffs and see how it works.

Just thought I'd let you guys know that you cleaned Brownell's out of their stops and the entire new batch they got in (81 pieces as of 6/3/05, Brownell's said their order came in May 28th) are all cut for 70- AND 80-series 1911's. If you have a 70-series, you should go directly to EGW to get one, either they sent the wrong ones to Brownell's or Brownell's ordered the wrong ones. They're ugly as sin on a 70-series.

Also, the picture at the Brownell's site is misleading on the -001 part. The image looks like untreated steel but they come blued or with a black oxide finish (actually I think the -058's have a black oxide finish).

I'm sending my FPS straight to EGW to have it exchanged with a 70-series stop. After George sees the Brownell's tag on the bag he says he'll try to straighten it out with them.

I just ordered 6 S-70 type stops directly from George. They were a little rough around the edges... looked to me like a dull end mill was to blame, but a few licks with a smooth mill file cleaned'em up slick as a button. Haven't done anything else except cut the radius and put'em back in the drawer to await assignment.

I sent one to a guy on another forum to fit to his chopped pistol, and he reports that it's like shootin' a different gun. Smooth cycle... Brass falls in a neat pile... Less muzzle flip and gets back on target quicker... An altogether worthwhile tweak, sez he... and he's gonna put one in all his pistols.

Wish George would make some stops in Stainless Steel for Series 80's. Sure could use some for my Colts

If the Sig GSR line starts up again in July or Aug. We can make some SS EGW OS Stops using the same materials. We will have to wait and see if a new PO is forthcoming.

I spent a chunk of time today reading this thread and then took a look at the FPS on my Dan Wesson. It's WAAAY relieved and rounded (and consequently, I noticed today a tad loose and starting to slip down and drag on the frame on one side). I had switched to a stiffer recoil spring to calm my insane brass ejection, but I'm beginning to think that a properly fit FPS would do me more good and protect my frame from unnecessary battering in the long run.

So, George at EGW got my order today.

I wanted to take the opportunity to thank Tuner, Fuff, Riley, and everybody else for the info in this thread. This is honestly something I NEVER would have thought of with regard to my brass flying 15' to my right. For that matter, it might have been a while longer until I noticed the slightly loose fit of my FPS, but since this thread got me looking at it I noticed it while it was just a little rubbing rather than having actual damage to my frame.

Hi everyone, very interesting thread and modification. I will be trying it out as soon as I get the stop from EGW.

Would someone be so kind as to post a picture of an EGW stop with a radius that is appropriate for a 5-inch .45 shooting factory loads? I remember reading that the radius can be adjusted differently for every type of 1911s intended use and am not sure what would be most appropriate for me. I have some confidence in my filing skills and I am going to try and free hand it, and I need an image to compare my stop with so I know when I'm done.

***EDIT***
I saw the pictures earlier in the thread, but they don't give me quite enough to go on. If I could see a side view it would let me see the angles of the radius better.

Most certainly. NYCMedic over on 1911.org did his first one about as well as I've ever seen one done freehand... so I swiped his picture for ya.

I use a slightly smaller radius for mine. This one is probably as close to the original .078 as you'll get it with a file and stone.

Perfect, per Canuck-IL's advice I will try to track down some sandpaper to do it with for more control. That is a very small radius indeed. What is the purpose of the small radius vs. the square edge that comes from EGW? Does it give the firing pin stop less "bite" into the hammer making slide movement require more mechanical energy?

The squared-off edge from EGW...

...will be sharp enough to wear on your hammer. If it's MIM, like my old SA Champion, it could clean the hammer right off with hot enough loads. I shot it about 100 times like this, and there was a definite mark in the hammer. I radiused it very slightly, and the wear ended there.

Slowing the slide. We have had a few discussions of the effect of recoil springs on slide recoil speed and also about hammer spring weights as an addition to this effect.

The conclusions were that slide mass has the greatest effect on the initial travel speed and that spring weight had little to do with initial slide speed. The higher the recoil spring weight outside the factory spec., the higher the felt recoil because the spring ties the slide to the frame and as weight goes higher it tends to absorb less and transfer more recoil to the frame. The recoil spring is much more a feeding spring than a major impact on initial slide movement although it does serve to slow the slide as it reaches the end of it's travel and the spring's force increases to rated weight.

A simple way to quantify the effect of a more sharply radiused slide stop would be to measure the difference in length from the hammer pivot point to the two points of hammer intersection between the two stops and then multiply that by the hammer spring rate, which will be far less than the rated weight at the point of initial movement. I would be surprised if it amounted to one tenth of an inch.

To get an idea of the forces involved measure the base of the .45 ACP case, compute area and multiply this times 20,000 PSI. The number will surprise you and this is the number we are working against with springs and mass. You will find that springs are a small factor when compared to mass in controlling the initial slide acceleration. Otherwise we could build pistols with very light slides and stronger springs and end up with lighter weapons. This hasn't proven to be the case.

As I have said before, a properly sprung 1911 pattern pistol will fire and eject just fine with NO recoil spring at all.

The fired case will land in the same area as they did with the recoil spring in place.

The cases will not be bulged.

There will not be a more prominent ejector mark.

I agree that the name should be changed from recoil spring to slide return spring.

Can we get a Constitutional Admendment?

Well... Here we go again. Rather than use bandwidth with calculations, I'll try to explain the "why" part of how this thing works like this.

Felt recoil in the autopistol is in three distinct phases. The three events occur so close together, that they seem to be one.

Phase one is the actual recoil... the "kick" of the cartridge firing. That one can only be reduced by changing ammo or... as jungle noted... by increasing or reducing slide mass. It is what it is.

Phase two is the effect of the recoil spring providing its own "Equal and Opposite" push between the moving slide and frame. The heavier the recoil spring, the harder it pushes the frame into the hand. The slide's velocity rearward also plays into the total effect. The faster the slide accelerates, the more sharply the secondary effect of a given spring's loading will be felt.

Phase three comes from the slide impacting the frame at the end of its travel. The harder the slide hits the frame, the higher the gun flips on impact. Hence, the less slide velocity that is available for that impact, the less the gun will flip. Also hence... the slower the slide accelerates with a given recoil spring, the lower the recoil spring's effect will be during the secondary recoil.

The smaller radius reduces the slide's mechanical advantage in overcoming the mainspring, thereby delaying the slide's initial acceleration during phase one.

Think of it as tapping the brake at the instant that you nail the gas pedal in a drag race. The elapsed time at the end of the race will go up, while the terminal speed in the traps will drop. No matter how hard the car accelerates after the brake is released, it can't make up for the lost time and momentum. If two cars that are theoretically identical... the braked car will lose every time.

In the case of the modified firing pin stop, the effect on felt recoil comes mainly in the tertiary phase... reduced muzzle flip when the slide hits the frame. It seems to be one of those things that fit the category of the whole being greater than the sum of the parts. The only suggestion that I can make is to try it for yourself. The proof's in the puddin' so they say... and arguing the point further won't convince anyone of anything until they give it a whirl.

Wasn't the small radius the original design?

Didn't the large radius we see so much today originate with the Colt Gold Cup in order to get it to better digest the "softball" 185gr target wadcutter ammo?

The first big radius I ever recall seeing was on a .38 Special Gold Cup.

Up until then all I had seen was the old GI type.

I can't recall which my Father's first year Commander had.

The stop was changed by the Army Ordnance Department after receiving complaints from the cavalry that the gun was too difficult to hand-cycle with the hammer down... and it is harder to do... which will provide a clue as to its effect on the slide's initial acceleration. Once the hammer is slammed rearward, the effect ends.

Quote:
Otherwise we could build pistols with very light slides and stronger springs and end up with lighter weapons. This hasn't proven to be the case.

One thing that has always struck me is how light Glock is able to make the slides (I am making a big assumption that much of the weight is in the slide) on their guns and how light they make them in general. They seriously undercut even the polymer competition by 6 or more ounces for quite some time. The closest I have seen is the new S&W M&P which weight 24 oz with no magazine. The 17 is 22 ounces and the 26 is 19 ounces, and the 21 is 26 ounces. Do Glock slides weigh the same as everybody elses, say a 1911?

Glock, like most other later automatics, use a cam on the barrel to control the dwell time - the time that the barrel and slide are locked together. By changing the cam surface dimensions the dwell time can be leghtened or shortened. Browning's link design works fine for its intended purpose, but one can't do much to adjust the dwell time, although some makers try by fooling around with the recoil spring. Within reason, if you can lengthen the dwell time you can lighten the mass of the slide. To my knowledge this was first done in the Browning Hi-Power in 1935.

It is interesting to examine the way factory engineers control slide speed with mass in the Browning style tilting barrel recoil operated pistols. Note the difference between the BHP in 9mm and .40. Heavier slide. H&K 9mm and .40. Heavier slide. Given identical guns within a group, one will almost always find that the engineering solution to controlling slide speed as bullet energy goes up is to increase slide mass. Colt chose not to do this with the Delta and ran into problems.

There is obviously a working range of weight and spring that is acceptable for a given energy. A 1911 in 9mm or .45 ACP will work with near identical springs, but the 9mm will have an easily felt slower slide movement. Colt's early solution was to introduce lightening cuts in the 9mm slide.Some people mistake the heavier spring in a heavier slide as a resistive effort at slide speed, but it is used to control the deceleration of a heavier or faster mass at the end of the recoil stroke.

If anyone has a Glock and 1911 and an accurate scale I think you will find the two slide weights very similar in .45 ACP caliber.

Part of this has to do with the fact that a larger cartridge (.45) usually requires a higher, and possibly wider slide because of the cartridge head size. But whatever weight advantage might be gained is lost if the slide is shortened to make a compact or sub-compact pistol unless other modifications are made to the shorter slides.

In his original link-based designs, Browning used the mainspring, hammer, and firing pin stop radius as an additional buffer on the slide. During the early 20th century it was not uncommon for individuals using the 1900 era .38 Colt's to cock the hammer before loading the first round into the chamber, and then lower the hammer on the chambered round. As Tuner noted, the Army didn't buy this for long with their new 1911 .45 pistols, but the design was good enough so that the pistol usually stood up to years of hard service.

During the development of the original Detonics pistol is was discovered that the slide - shortened by 2" from a Government Model - had a slide velocity that was increased by as much as 50%. But oher factors were at work besides lighter slide weight, including a shorter dwell time caused by the barrel dropping at a sharper angle.

Understood, but it is undeniable that modern designs use slide weight to control slide speed across the board. Compacts will be seen with thicker slide cross section than their full sized counterparts. The 1911 is a poor example of this, because the compacts keep the same cross section, but it is obvious that reliability suffers as slide speed increases due to lower mass.

In the case of Glocks, longer slides have lightening cuts to retain the same mass as standard sized slides. SIGs and H&Ks will be seen with thicker cross section through portions of the slide as the energy of the round is increased. Beretta quickly discovered reliability problems in previously very reliable pistols if slide mass was not increased in the move up from 9mm to .40. Rim diameter doesn't mean much, since almost any slide is wider than common rim diameters. Energy is the key and will have the most effect with respect to slide mass and velocity.

I haven't gotten the part yet so I can't make any claims as to the efficacy of the modification, but maybe this thread is worth adding to the 1911 clinic.

As an FYI (don't know if it had been mentioned in this specific thread) but S&W 1911s require a series 80 firing pin stop.

Quote: Given identical guns within a group, one will almost always find that the engineering solution to controlling slide speed as bullet energy goes up is to increase slide mass. Colt chose not to do this with the Delta and ran into problems.

Colt dropped their candy with the Delta when they missed the opportunity to utilize more of the mainspring's effect by going with a 25-pound mainspring and getting back to the basics on the firing pin stop. Ted Yost and Ned Christiansen figured it out in about two shakes, and I understand that both of these world-class pistolsmiths use a very small radius on the firing pin stops in their Big 10 pistols... and they do it with less recoil spring than the factory standard of... IIRC... 22 pounds.

Colt... All it woulda taken is a peek at the old blueprints and for somebody to notice and ask: "Why"

In the case of the Delta, springs where a bandaid when greater slide mass was clearly called for, and the results were never satisfactory.

Quote:
In the case of the Delta, springs where a bandaid when greater slide mass was clearly called for, and the results were never satisfactory.

No doubt that the slide could have used another ounce or two... but Ted and Ned seem to have gotten it sorted out in fine fashion... and they're dropping down to 18 or 20 pounds on the recoil spring as a matter of habit, so I hear.

Some of the guys who have tried the combination of small stop radius, 165 PF ammo, and a 23-pound mainspring are reporting short cycles with even 14-pound recoil springs... so the effect isn't imaginary.

165PF is slightly under par for .45 ACP, a full power 10mm is a completely different animal and should have been dealt with accordingly. The 10mm exists in a form close to .40 S&W and any Delta can handle that, but the original full power loading is beyond the normal 1911 capability without some serious mods if the life of the pistol is expected to remain long.

165PF is slightly under par for .45 ACP, a full power 10mm is a completely different animal and should have been dealt with accordingly.

I know that 165 PF is light. The reference was made to show that the stop radius does have an effect. Uhm...Maybe you should contact Ted Yost or Ned Christiansen for a full report on how their 10mm pistols do over the long haul. like I said...They seem to have gotten it all sorted out.

I think they would both agree that a 1911 will live a very long time with 165PF loads and a considerably shorter time with full power 10MM loads regardless of springing or FPS radius.

"P" Factors

As will anything that imparts higher energy and pressure against a breechblock. 38 Special vs .357 Magnum, etc.

What I'm curious about is how the thread went from discussing how using a small radius on the firing pin stop makes a .45 caliber 1911 sweeter to shoot, to how brutal the 10mm is on a standard 1911 frame and slide... about which I completely agree. The slide should have been beefed up.

Maybe you should invest 20 bucks in a stop and a new 23 pound mainspring and try it for yourself...

You know me Tuner, I'm just not very sensitive to the subtle changes some report with various modifications in spring weights. My first post outlined a simple way to quantify the change.

I guess you could say I don't see a problem to start with and remain somewhat skeptical of the actual effect this mod may have. Having seen different people report widely varying impressions of recoil with an identical pistol and ammunition, I am less inclined to trust impressions(my own included) and more inclined to trust hard data.

Lacking hard data in the form of high speed photography, the next best thing might be ejection distance with a pistol fitted with the two different stops firing identical ammo and fired from a Ransom rest to ensure identical hold. I don't argue that the mod doesn't change anything, I only question the amount of change.

I can of course alter ejection distance with recoil spring weight also, but that doesn't imply the pistol is running better or worse as long as function is not impaired. Only that slide speed at the end of the recoil stoke has been altered slightly.

There is also the question of ammunition tolerance, with a given slide weight the lighter spring will allow a wider tolerance of loads to be digested by the pistol.

Well... The difference isn't really that subtle. Most report a definite change in the recoil charactistics of the gun, while others report only a faster target reaquisition and split times... but sometimes even subtle changes are worthwhile. Every little bit helps... just like with the 10. it's not about making the gun indestructible. Can't do that unless the gun is never fired. It's about prolonging the useful life of the gun. That's why we change recoil springs and lube slide rails. As far as ammo sensitivity goes, I don't see it. My ammo ranges from 230/850 down to 200/750 fps with 16-pound recoil springs... but either will run all my guns with even an 18-pound recoil spring. Only yhe ejection distance changes. The 200/750/18 combo dribbles the brass out at my right foot... but I don't get short-stroke malfunctions. A different gun just might have a problem. Simple matter of dropping to a lighter recoil spring... which also helps tame the effects of (secondary) recoil on the shooter.

Really though... You should try it. Ya might find that ya like it a lot.