We've got a few good threads going of late. While all of the cogitatin' juices are flowin', I thought I'd chunk this one into the mix. Actually, I'm just tryin' to further confuse Jon! He's been gettin' too much sleep lately.
OK. The slide spec call for the breech face to be machined at 89 degrees, 08 minutes off the horizontal datum line. The locking lugs recesses are supposed to be machined at 52 minutes off the corresponding datum. No confusion there. That adds up to 90 degrees. Now the barrel is, I'm sure supposed to lock up at that same angle in a best case scenario, which would result in the barrel lugs mating with the lug recesses and have full contact across the lug face. This all assumes (there's that word ) that the barrel lug depth, standing lug fit, etc, etc are all in spec. We all agree (just nod your head north & south) that the hood should be fit to a close fit with the breech face. Now we know that on a GI spec/similar gun, the barrel fit will be some what less than what we would prefer for a long wearing fit (loose hood, slap peening, etc).
Now we get to the meat -
We fit a match barrel to a (match grade or refit) slide/frame. The variables are still there with the production tolerances of the slide/frame and the barrel may seat deeper as we seek the magic amount of lug engagement. So the lockup angle of the barrel may vary slightly resulting in a point or line contact of the mating surfaces in the barrel & slide instead of full contact. It's simple high school math. In fact, it's either full contact or not. There will be no line contact possible without some distortion of the lug face, so it's full contact or point contact, at least initially. Now I can see that this is not terribly significant in a 5" 45 as long as all else is fairly straight. It's a low pressure round. The lugs will probably pressure seat over a couple hundred rounds. The tighter the hood is fit to the breech, the less looseness will develop from this process. Of course that doesn't even address the case head to breech face interface that will be altered with any change in barrel lock up angle.
Change that to a high pressure round and the ante gets upped a bit. Race guns in 38S, 40 should show this before any others due to their use.
Change the length of barrel & slide and you really change things. The barrel lock up angle is significantly changed. I'm pretty sure that none of the manufacturers cut the slide lug recesses nor the breech face at a different angle on the shorter slides. If I'm wrong, someone show me the blueprints so anotated. I've got OACPs and Detonics that I've shot a reasonable amount, but not enough to draw conclusions. And they are in 45, not 38S, etc.
So, my question for the smiths and LOGs of the board is what effect if any have you observed with this over time? Enquiring minds want to know (well at least my little pea brain). Lest anyone be confused, I'm not worried, just very curious.
That's enough for now. My fingers are tired of hunt/peck and I'm sure that any more would cause Jon to freak!
OK! Let's call #1 lug .050" tall.
That there 52 minutes of angle amounts to approximately .0008" over the .050" height. Or about 3/4's of one thousandths of an inch.
The barrel lugs are not machined on an angle.
Insignificant.
Excellent BBBBill, and Chuck, the barrel isn't machined on an angle because it is square to the breech, so it mates, you knew that. Also the variations by slightly greater or lesser degree as in perfection. The barrel could be said to be tangent to the breech face, an arc at tangent is pretty close to square either way slightly off center. Sorta. I don't see the case caring as the chamber clearances are great enough for the case head to get square when the primer pops.
Got done with the yard and checked the Detonics and the Officers and both breech faces are the same at just under 1 deg or 52' and the barrels are 1 deg 30' as best I can tell with an electronic level, sorta hap hazard but an indication, mathematically it comes out to 1 deg 20' depending on the numbers your using, ahh yeh. So it does appear to me that the powers to be said ehh it'll be fine.So, BBBBill you're right. I've known that the barrels on the shorties are more noticeably on an angle, but never checked to see how that was worked out. Hey they work!
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The barrel lugs are not machined on an angle. Insignificant...
Yep, concur about the barrel. That is what generated this train of thought, since the lockup angle can be variable and the lug angles are fixed. Insignificant? Probably... maybe... I'm no expert, so I'll defer. It does pique my interest though.
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...checked the Detonics and the Officers and both breech faces are the
same at just under 1 deg or 52' and the barrels are 1 deg 30' as best I can
tell ... it does appear to me that the powers to be said ehh it'll be fine.
So, BBBBill you're right. I've known that the barrels on the shorties are more
noticeably on an angle, but never checked to see how that was worked out. Hey
they work!
Thanks for checking. I calculate a barrel angle of 1 degree, 22 minutes on an OACP length gun. So that leaves a mismatch of ~ 30 minutes (1/2 degree). Again, not a worry, just an exercise in learning more about our favorite platform. Just curious to see what folk have observed/will observe as relates to the variations in fit due to link up heights/slide length. I'm currently convinced that firing will eventually coax the barrel lugs to move (cold flow?) a bit to get more contact, i. e. from a point contact to full contact. That movement on a well fit barrel will, IMO, not change fit enough to matter due to the shallow angle. I think, hypothetically, on a short barrel gun in 38S/40S&W, that it might loosen up a bit sooner/more due to the higher pressures/more vigorous recoil/steeper lock up angle.
I'm still open to more feedback from the wiser/smarter/handsomer-than-me folks.
As long as this is just for fun I licked the end of my pencil, knotted up my unibrow, and figured it from a different angle. (unintended pun)
Machinists, which I am not (I'm just a hack), say 1 degree angle over 1 inch will indicate .017in.
.050in lock-up for a 5in bbl gives .010in per in. of run
.050in lock-up for a 6.5in bbl gives .0077in per in. of run.
.050in lock-up for a 3.5in bbl gives .0142in perin. of run.
So it is 10/17ths, 8/17ths, and 14/17ths respectively.
Shorter barrels show a greater proportional change of angle then longer barrels.
The real world result with only a change of .050 vertical travel is so insignificant (as Chuck pointed out) it still works (as Log pointed out)
I had a shot at figuring percentages, but my pencil got so confused I had to throw it away.
I think cold forging or hammer forging would be the term you were looking for BBBBill.
What this all means I have no idea. Not a math guy either.
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Excellent BBBBill, and Chuck, the barrel isn't machined on an angle because
it is square to the breech, so it mates, you knew that. Also the variations by
slightly greater or lesser degree as in perfection. The barrel could be said
to be tangent to the breech face, an arc at tangent is pretty close to square
either way slightly off center. Sorta. I don't see the case caring as the
chamber clearances are great enough for the case head to get square when the
primer pops.
Hi Log; Some years ago, I modified a sine plate that allows me to to attach the complete slide / barrel combination with the barrel locked in battery. Placed on a surface plate, I can calculate the exact angle of the bore C/L. No two combinations are ever the same. Differences are not major, but enough to make a difference. It doesn't really matter to me what the angle is, I just need to know the distance the plate is moved to bring the bore C/L parallel. Then it can be transfered to the bushing. In fact, the angles are usually less than the blue prints indicate.
Upper Lugs; Almost every barrel needs the upper lug distances machined to exactly match those in the slide. The presumption that all match barrels exactly fit all slides is erroneous.
I don't believe in pressure seating. Only proper fitting in the first place. Done correctly the gun will shoot 10s of thousands of rounds with virtually no wear in the lug area.
quote:
"Differences are not major, but enough to make a difference. It doesn't
really matter to me what the angle is, I just need to know the distance the
plate is moved to bring the bore C/L parallel. Then it can be transfered to
the bushing"
Jerry, pull out that camera next time you fit one. I'd enjoy seeing this theory in practice.
Interesting question as usual.
If we asume the pivot point is the front of the bushing.
We measure lock up at the back of the lug engagment (not the back of the hood)
what is 0?
the bore in this slide is .700 for simplification?
the barrel diameter is .694 (match barrel.)
So if we push the barrel up against the top lugs out of battery to set a 0 start point, it is already up 1/2 of the difference of the bore (.700) to the barrel (.694 devided by 2= .003)
Not sure what you shoot for or get for lock up. Say .047
So barrel length of 5" minus hood lenght of 1.314, minus barrel stick out of bushing. Than find the angle of .047 plus .003 = .050 lock up at that length.
Was helping a couple guys fit barrels in the shop tonight and both the lugs engaged the barrels and made first contact on the sides of the lug face not the center.
This would seem to indicate that the barrel lock up angle would be less than the angle the lugs were cut on. If the slide lugs were cut on 0 angle we would expect the barrel contact to be in the center of the top lugs yes?
This does not include (and probably it does not matter) that the barrel drops down below 0 angle when unlocked and the lugs pass each other hopefully wthout eating each other.
I get approximately .8 sine which would be less than the 52 min the lugs are cut on.
Never thought about the short guns, even with the same lock up, having a steeper angle and affecting the sight height. Maybe not from barrel time but from the steeper angle the equal lock up gives over the shorter length....
geo, www.egwguns.com
This is some impressive math going on here. I'm quite certain when I signed up for this forum I was told there would be no math.
I'm not as into the details as others, I just enjoy shooting my guns, and learning enough to take care of them properly. My Gold Cup out shoots me, so the problem does not currently lie in the gun, but in me.
When I get some time, I'm going to try to make some grips from some plate aluminum I have (1/4" thick).
I for one agree! Although I don't see or understand that a difference of opinion has been shown or expressed, just different degrees of understanding and the relevance of the understanding projected into the fitting of the bushing. Perfect angle bore, based on the numbers. Can't see any disagreement about upper lug equalization. And machining has to be the best way to do it.
Although in regards to upper lugs I've had this crazy thought to get them as close as I could with my v-block and then fit the hood so tight that it has to be tapped up and then use a slide hammer that runs out the end of the muzzle and anchored in the chamber by a case sized plug and just give it a lot of light taps to settle high spots and then see if I still need to take that last .0005" off the hood. Kinda inspired by the kids in third world countries building functioning AK-47 with hammer and chisel.
Because I'm not a math guy, I'm going to sit the rest of this out with a beer.
It's getting interesting, really interesting.
A little slide hammer. How come I didn't think of that?
The math part can be fun from using the sine tables in a machinist hand book to using the rise, run, pitch function, of a construction calculator.
Okay, sine tables are most often printed for a 5" sine. So when working with other number one has to interpolate (adjust) to represent the 5" so the tables can be useful. Jerry's modified sine bar gives him direct readings. So if the pivot points of a 5" barrel are 3.50" for example and we have .053" of engagement then we can look it up in the sine table by dividing 5 by 3.5 and multiplying the answer by the engagement which makes it relative to 5". 5 devided by 3.5 = 1.4502 X .053 = .076861. So look up on the sine table and we find that the closest number is .07563 which represents 52'. If using a construction calculator and use 3.5 as the run and .053 as the rise we get .87deg or .87 X 60'= 52.2' or 52' 12" this justifies the two methods. Fun stuff.
Geo. adjustment of .003" is valid for calculating the angle from bore center line. so if the engagement where .050" in the above example the rest falls into place. Are these critical things for us to know. Better is always better. Just good to understand what these heavy weights are getting at!
I am setting up some new machinery at present time. When I start back into the barrel making, I'll take a picture of my gizmo. The sine plate has a pocket machined into it that allows clearance for the lower lugs. The slide is clamped flat onto the plate. There is a set screw that adjusts up from the bottom to position and hold the barrel in lock up. A piloted taper pin is insert into bore, and the sine plate is raised until the bore C/L is level, using an indicator/surface plate... I then transfer 1/2 that figure to the bushing, making it more compatible to the barrel lock up angle.
The advantage is, you can run tighter barrel/bushing clearance, with full 360 degree contact and still lock and unlock without spring or tension. No grinding of clearance at the top and bottom of the bushing... equals more support.
If the gun is ever fired with a proof load the initial set of measurements are going to change anyway.
If you had point contact the metal is going to deform and increase the contact area.
Don't know what's required nowadays, but in the '80's only the barrel of a semi auto was proofed.
I did shoot a couple magazines of 357 Mag proof loads, but I was young and immortal then.
Do not do that.
Because no proof loads would go through a finished pistol it's sort of a moot point.
This is fascinating stuff guys - the sort of stuff I like to get into up to my knees and study. I had not even thought about the change in angle Mr. George mentioned as barrel length departs from 5" in length, so this thread has already added to my understanding. The neat part (to me), though, is that I believe I understand the conversation. As always, thanks for the continuing ed.
That for all the discussions of what the mating area and surface contact is in a 1911 it is still subject to alteration by proof loads and the repeated firing of the gun.
While the lockup may have less than full contact and engagement intially, use is going to alter that.
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That for all the discussions of what the mating area and surface contact is
in a 1911 it is still subject to alteration by proof loads and the repeated
firing of the gun.
While the lockup may have less than full contact and engagement intially, use is going to alter that.
Unless you never actually fire your guns.
And so holding clearances and dimensions hasn't any value? Oh well, it's just going to change so why bother to fit as well as possible.
Pretty well understood by most that a poorly fitted gun is going to have a shorter life than a well fitted one. No?
If the hood is fitted so there is very little detectable movement between barrel and slide, that will improve life and accuracy. Why cut the hood short, and turn the slide into a slide hammer on the barrel lugs?
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And so holding clearances and dimensions hasn't any value? Oh well, it's
just going to change so why bother to fit as well as possible.
Your comment, not mine.
Accurate fitting can be taken to an extreme with no regard to how the gun is going to function if you want.
Pretty well understood by most that a poorly fitted gun is going to have a shorter life than a well fitted one. No?
If the hood is fitted so there is very little detectable movement between barrel and slide, that will improve life and accuracy. Why cut the hood short, and turn the slide into a slide hammer on the barrel lugs?
Cause the hood is not the only thing the breech face hits against?
And how does that change how hard the barrel lugs will get hit?
Changing the area the slide uses to move the barrel is not going to alter how the barrel comes to rest.
Spend as much time fitting as you like.
There just comes a point that it has zero additional result for the work required.
Do you stop and sharpen your knife after every cut?
Do you adjust the fit of your gun after every round of shooting?
Getting the action to repeat alignment after every round os the goal for accuracy.
Accuracy stays good after some break in (where the parts wear into each other), and then starts to suffer as wear takes its toll on the fitting.
25,000 PSI and the forces it produces in moving parts has a way of wearing things.
That is the point of fitting the hood close, so the lugs don't slam. I believe I gave you this example of two trucks slamming into each other from a foot away and starting with the bumpers touching.
The end of the hood is the only thing that should touch the breech face. Correct.
And yes of course things wear and how well fitted will set the stage for the progression. Better is better. If attainable you can't get better than perfect.
A sharp knife does stay sharp longer a cutting tool will last and last as long as it is sharp and cutting, but dull, the edge will be destroyed.
Log mentioned something about me and a sine plate some time back, and jogged my memory.
Anyway, here's a couple of pictures that will give you a rough idea of the fixture, etc.
BBBBill, the breech face is also machined at an angle, right? Does this angle changes with barrel length, as it should?
How perfect can the slide/barrel lug engagement really be?
What is "perfect" (or close to it) to start with?
I assume both lugs engaging? what percentage? radial, top end, or both?
How many normal pressure rounds will it take to significantly increase the contact area?
Kuhnhausen in Volume II has a little bit to say about this on page 138 in reference to commander size 1911s. Nothing earth shattering, but interesting non the less. He talks about the lugs hitting on a point or edge and getting beat into alignment with use.
Here's my take on this discussion. I'm throwing this out there so hopefully someone will jump it if it's wrong.
The barrel (5" 1911) is angled up in the slide 52'. The slide notches for the barrel lugs are likewise angled, 52'. That permits the barrel to be machined square, 90degrees for the lug faces.
The smaller 1911 variants (i.e. officers), will have by virtue of their shorter barrels, angles steeper than 52', but log measured a detonics at 52', so at least detonics thought it was a don't care (or maybe a don't know). Also Kuhnhausen's commander discussion makes me think that the angles are perhaps not quite correctly machined for the smaller pistols.
Various gunsmiths (professional and otherwise) have different ideas about measuring and correcting errors in the lug fit due to the angle.
Here are some thoughts... nothing original but I'm curious...
1. Would taking a cast of the slide lugs as is sometimes used to measure the lug spacing be of benefit to fitting the barrel lugs?
2. Would trial and error fitting with hi-spot blue be of benefit. One could see the lug contact on the edge or point and then file a little, refit, etc.
3. Would the use of plastigage be of benefit? Has anyone tried it to use it for firearms? http://www.plastigaugeusa.com/
Over the years, I became determined to perfect fitting of the upper lugs. We can do a very good job of the lower lugs, but the upper lugs are another matter. My goal is to achieve maximum contact as a means of increasing stabilization of the barrel for accuracy enhancement. Accurate measurements are a must, and difficult to do by ordinary means. By accurate, I am talking repeatable within "tenths". I take all the measurements in the lathe, with a tenths test indicator, and the lathe DRO, which is accurate to a tenth. This is a very accurate system of measure, and does not involve a lot of time or hassle.
I make the horizontal adjustments(cuts) in the lathe using a Kennametal carbide grooving tool. I also adjust the lug radius, and depth during this time, so that it will match the slide lug radius, and depth to place the firing pin in the center of the bore. Barrels and slides vary greatly in horizontal distance and radius. I doubt that anyone would have much success filing the lugs in an effort to get a match on all three lugs. Some require a fair amount of material removal. As far as percentage of radial contact: First the radius of the slide must be cleaned up by lapping. With the exact slide radius known, that radius can now be duplicated on the barrel. Problem is, todays barrels are not machined with a perfect radius, and depending on the firing pin depth, may or may not clean up to precisely match the slide radius. I have never had one clean up to match 100 %. They are machined and engineered to lock up at 10 & 2 o'clock. The 12 o'clock area of the groove is lowered to prevent contact. Yet other barrels are designed to lock up at 12 o'clock and are shallow at 10 & 2... I don't use the 12 o'clock barrels at all.
The 10 & 2 barrels will often clean up with 60/80% contact. A good improvement over small spots at 10 & 2.
But, the only way to get perfect, full contact fit, you'll have to machine your own barrel from a blank. I consider this the ultimate barrel.