Barrel guide blocks or hood?

I have been struggling to understand what interface should stop the barrels rear motion. Edit: Stop the slides forward motion.

Do the guide blocks in the slide or the barrel hood/breach face stop the slides forward motion while the barrel lifts into battery?

It depends on the gun, as it could be either.

When in battery the average, recently manufactured Gov't Model 1911's barrel is pushed forward by contact between the slide's breech face guide blocks and the chamber face. There will be a gap of about 0.006" between the barrel hood and breechface. And as long as the barrel and slide are within specs, the hood will never touch the breechface. The mathematically derived (from the latest Army Ordnance blueprints) value for the hood-breechface gap is 0.006 +/- 0.004 inch.

However, slides and barrels manufactured to earlier (1944) Army Ordnance blueprints could have hood-breechface contact because the mathematically derived value for the gap is (rounded to the nearest thousandth) 0.002 +/- 0.004 inch.

For other guns, it could be either contact: hood-breechface or chamberface- guide block.

What about when the barrel is sweeping a circular path entering battery? There should be a gap between the hood and breechface while in battery but what about while it is going into battery? ( I had a barrel "wagged its tail" entering battery)

More info: I visually determined that my barrel starts to contact the barrel guide blocks in the slide first. Then there is a glancing blow between the hood and breechface and finally the slide stops again on the guide blocks. All of these interactions cause the new barrel to move a little from side to side.

Now I a curious about how it should work.

I don't think the difference in the angle of the barrel between linkdown and battery (0° 52' or 0.87°) will make that much difference. Even though the breechface and the guide blocks are that same angle ahead of the vertical, the initial contact when the barrel's linked down and essentially horizontal would be either at the upper portions of the chamber face adjacent to the hood or, perhaps, at the hood itself.

Here's a crude drawing of a recent Gov't Model in battery:

PICTURE 404

Not sure what you mean by a barrel "wagging its tail".

I guess we cross-posted and I missed where you explained the tail wag.

Only thing I can think of at the moment (never having heard of it before) is it occurs because the barrel-slide dimensions are really close to having contact in both places. But why the contact would shuffle back & forth on the way into battery escapes me. Dunno.

I also don't know whether it would do that when fired and if it did... well... what the consequences would be. If there were any consequences.

Interesting.

One more observation: As the barrel sweeps through its upward travel into battery it initially contacts the guide block on the side below the extractor. Then the opposite guide block contacts as the barrel lifts across the extractor tunnel. Lastly the barrel contacts the guide block on the side above the extractor tunnel.

I never read about this interaction when "fitting" a barrel.

I was initially mislead by the Kart barrel fitting instructions because Kart warns that uneven upper lug-pad contact can cause barrel side motion. This motion lead me to keep filing the barrel lug-pads when in fact it was the guide blocks that caused the barrel side motion (tail wagging).

I got frustrated trying to eliminate the tail wag so I installed an OEM Colt barrel while I figured all this out. The Colt barrel shoots fairly well and I use it as a baseline performance point.

But then I installed the original Metroarms barrel to compare yet another data point... lo and behold... the original barrel wagged its tail too... analysis paralysis set in and is entered a metal coma for a while.

I did manage to eliminate most of the tail wag by truing the guide blocks with my hammer hook file... but is this normal?

Quote:
I never read about this interaction when "fitting" a barrel.

After 100 years of mass produced guns, countless interpretations of blueprints, which in reality, have been adjusted to ease manufacturing, it's no wonder things have become so convoluted. Mass produced, and many custom guns, are an aggregate of compensations.

Contact with the slide guide blocks should not occur ...only the hoodface/breechface. I machine the barrel edges if I need clearance. Because Bullseye guns make hard contact between the hood and breechface, I rarely have to clearance the barrel on the sides... but the need does occur.

The barrel is often, I should say most times, not centered in the frame and or slide. The lug cut out in the frame and the C/L of the slide upper lug radius, is usually not correct, on top of the fact that the upper lug radius in the barrel has its own C/L. Before the barrel can operate without a divergent force, these C/Lines must be compatible.

Maybe that's the advantage (?) of fitting a true NM-style barrel with an extra long hood so there's only hood-breechface contact, with never any contact between the chamber faces and guide blocks?

If there is any practical advantage, I wonder how much accuracy improvement is gained? A teeny bit? A LOT?

Can't answer your "Is this normal?". This is all something brand new to me. Maybe somebody else knows and will chime in.

Quote:
Contact with the slide guide blocks should not occur.

What do you mean when you say "should not occur"? If the Army blueprints show it occurring, it's hard for me to understand why it shouldn't. I can see where a sub-MOA 1911 might need to be built to different standards than a range beater or carry gun, so I can see why the adjustments you describe may be necessary for Bullseye, but I'm not sure Eric is building a bullseye gun here.

Quote:
Contact with the slide guide blocks should not occur.

This makes a lot of sense. None of my other three 45s show any indication that the barrel is contacting the guide blocks.

I am working on a Metroarms American Classic II because I bought it for less than I could find a good used 45 for. I changed out mostly all of the parts for the learning experience and to make a more durable pistol. I fully expected to find some aspects of the Metroarms not to print.

The good new is that I know more about how to fit a new barrel now. I thank you for this knowledge.

It may well be that, for instance, a GI hood is cut with relief for maximum reliability when dirty, but that maximum accuracy is achieved with hood/breech contact. That would mean that, if I were building a carry gun, I might choose to have a somewhat shorter hood for maximum reliability when some lint or dirt gets in there, but if I were building a bullseye gun, I would make that zero to minimize my groups. (I don't actually know, I'm just guessing here.)

But when someone says that the something shown in the Army prints is categorically incorrect (rather than a poor choice for a particular application), I'd like to know why he thinks that. Or, really, if he actually thinks that.

I've learned from 1911Tuner here that the first and best reference is the group of relevant JMB patents. Browning explains therein much of the reasoning for his design decisions.

Many of the current practices in pistol "configurating" are the direct result of the quest for "accuracy." Niemi24s has kindly interpreted a number of USGI drawings to show the tolerances specified result in what we must infer to be "design" clearances.

The bottom line is that the purpose of the pistol has evolved from a battlefield weapon to a precision mechanism operating in a relatively benign environment. The buying public resists a "rattler," even though the clearances may conform to the GI prints, and frame-to-slide fit be the least important factor for accuracy. The exception to the latter statement is, of course, pistols with frame-mounted optics or which are tested in a Ransom Rest.

As you have rightly stated, the purpose drives the build, and the purpose has wandered a fair piece from the original purpose for which the prints were drawn.

I meant to stay out of this one as well, since the "US Army's blueprints" do seem to indicate that guide block to breechface contact is acceptable... but it's not, and like the barrel standing on the link issue... I've only seen it rarely, and when I do... I strongly suspect kitchen-table tinkering. Not wishing to get wrapped up in an endless debate over this... I kept out.

Guide block contact that occurs in ordnance-specg guns isn't the issue it is with tightly fitted guns in which it occurs because the slide isn't pressing on the barrel and forcing the upper lugs into engagement... but even in the looser pistols, it usually causes the nose of the extractor to wallow out the right edge of the barrel.

Close fitting between the hood and the breechface offers two advantages... both to accuracy and durability. It causes the barrel to return to battery as closely as possible to the same place between shots, and because it forces the barrel as far forward as horizontal lug engagement will allow... it negates the tendency of the lugs to batter under recoil due to the "running start" they get at one another in the loose pistols when the barrel is jerked forward from bullet entry into the rifling while the slide is hammered in the other direction.

For service/duty/carry guns, I like to see just a little clearance between the hood and breechface. .003-.005 inch seems to work well. A Bullseye pistol is a different animal. As Jerry has demonstrated, you can't just take an ordnance-spec pistol... tighten it up and hard-fit a barrel to it... and go shoot at Camp Perry with any expectation of making a good showing.

Yes, my Metroarms is a "Shade Tree Mechanic" (Kitchen butcher job ) build and I never pretend if wasn't anything other than a hack job. But it was the best choice available for a learner pistol. I never even considered hacking my Colts or Springfields. With the confessional over now:

Thanks again for the clear explanation. I have three barrels available for the Metroarms in the parts bin now. The OEM barrel, a Colt government barrel, and a Kart barrel that I attempted to fit to educate me on how this pistol works and maybe-just-maybe shoot better.

They all have their advantages and disadvantages but they all function well.

Now I have reached an interesting decision in my path to a durable range beater. OEM, Colt or Kart. I need to choose soon because the poor slide lugs can't take any more barrel swapping.

I will see which barrel has the least "running start" to avoid battering the slide lugs any more than they already are.

Not to fret, Eric. The Kitchen Table Tinker comment was meant for the barrel standing on the link issue. Usually the result of somebody installing a long link in order to get the gun to "lock up" like the proverbial bank vault. The other possibility is an out of spec lower barrel lug. Either one will stand the barrel on the link.

It's entirely possible to assemble a reliable and acceptably accurate gun at the kitchen table if all or most of the parts are within spec. It probably won't be a serious threat at Camp Perry, but can be entirely adequate for almost anything else.

Guide blocks hitting the breechface are the result of an out-of-spec component... either the slide or the barrel. Most often the result of buying a new, "genuine" USGI barrel at a show that happens to be a government rejected part... due to being out of spec.

That's why ya gotta be careful when buying genuine USGI replacement parts these days. All the really good ones that were available in the 50s and 60s are long gone, and while you might get lucky... it's not the way to bet.

Quote:
Guide blocks hitting the breechface are the result of an out-of-spec component

If you meant to say "Guide blocks hitting the barrel chamber face...", then I beg to differ when it comes to a Gov't Model M1911A1 that is within recent (1970's) Army Ordnance specs:

* The longest possible in-spec barrel hood is 0.149 + 0.005 = 0.154 inch, as shown here:

PICTURE 404

*The shallowest possible space between the breech face guide blocks into which the hood fits when in battery is 0.159 - 0.003 = 0.156", as shown here:

PICTURE 404

Because the hood can therefore get no closer to the breechface than 0.156 - 0.154 = 0.002", it seems logical to conclude:

* It is impossible for the barrel hood of any Gov't Model M1911A1 that is anywhere within U.S. Army Ordnance specifications to come into contact with the breechface either on the way into battery or when in battery.

* Because the only other mechanism for getting the barrel into battery is by contact between the breechface guide blocks and chamber face - this how it must happen in an in-spec Gov't Model M1911A1 manufactured to and remaining within post-WWII Army Ordnance blueprint specifications.

* Any 1911 with a barrel driven to battery by hood-breechface contact is either:

--- an "extreme spec" 1944 (or earlier) vintage Gov't Model M1911 or M1911A1,

--- an out-of-spec (by manufacture, wear, or parts replacement) post-WWII vintage Gov't Model M1911A1, or

--- just a "1911", maybe even a $3,000 custom 1911.

All the above is based on nothing more than Ordnance blueprint data. There's no "right", "wrong", "should", "ought to", "I think" or "I've never seen" stuff involved. All the various 1911's we've got today are based (perhaps even loosely) on those Ordnance blueprints and IMHO understanding them is the key to understanding how all the variations of today work - or don't work.

If, however, you meant something else (see first paragraph) then sorry for the blather.

Dan... you can show all the drawings you want... but I'm basin' my statement on 45 years of handlin' and shootin' and wrenchin' on mostly USGI pistols. That contact was pointed out to me about 1967 by my uncle... and his experience went back to the late 30s as a Navy Armorer. The issue that he showed me was the extractor beatin' the soup outta the chamber face on the right side... and that it was rare, but still somethin' to keep a lookout for... because it means that somethin' about the barrel or the slide ain't right.

Quote:
...the extractor beatin' the soup outta the chamber face on the right side...

Good Heavens, we're talking about two different things! Kinda like when you and I were little kids and went to different schools together!?! Anyway...

...yes, the nose of the extractor can indeed extend forward of the the guide block, and by as much as 0.005" in an in-spec gun if the tolerances stack up the right way. But that's with the extractor at the forward end of it's slop range in the slide.

Even though there will be a minimum of 0.013" of slop (allowing that particluar extractor to get pushed back flush with the guide block), that extractor could and would, I suppose, play havoc with the chamber face - especially considering the friction between the extractor and its tunnel.

However, if all the parts are somewhere within their spec ranges, an extractor at the aftward limit of its slop range in the slide can never protrude beyond the guide block - no matter how the tolerances stack up. And that's probably a real good thing cuz I'd guess the extractor would soon break.

Nah... We're talkin' about the same thing, but we're thinkin' about it in a different way.

You're still huntin' zebras.

Static, some of them will make light contact when the barrel is pushed rearward in the slide as far as it can go... and even that's rare because the lugs won't let it move far enough rearward... unless something is wrong. Not right, but still possible. Dynamic... as in firing... it won't touch. Feeding... it won't touch. Firing further spreads the barrel and slide apart. No touch...

...unless something is wrong.

Pushing the barrel hard forward into horizontal lug contact and causing the extractor damage on the barrel? Rarely... and only if something is wrong.

That contact is one of the things that I always checked for when I contemplated buying an old GI pistol. I took along a .003 feeler gauge. Slide off... barrel pushed to the rear... if the gauge wouldn't slip between the breechface and barrel face... I had the option of offering less money or leaving it there. It depended on whether or not the chamber face had a slight angle on it. It the angle was present... I left it. If it wasn't... I knew that I could correct it or replace it because the issue wasn't likely in the slide. There were a good many "genuine" USGI pistols showing up that had been cobbled together from this and that parts... some rejected out of spec... and sold as the real McCoy.

Supposing that the extractor is on the short side of spec (or is dressed to avoid barrel contact), such that there's no risk of damage, what is the harm of guide block-barrel contact, even hard-in-battery contact?

I tried to dress one back once to stop the damage in a last-ditch attempt to save a slide. Wound up with an extractor claw so thin, I couldn't trust it. The slide was so completely out of spec that I wound up fillin' it with lead for a weighted drawing aid.

Beware of "genuine" USGI parts at gunshows.

Quote:
You're still huntin' zebras.

If figuring out whether a peg will fit in a hole by examining their blueprints is hunting zebras, then so be it - I'm a zebra hunter.

Quote:
Static, some of them will make light contact when the barrel is pushed rearward in the slide as far as it can go

If a recent 1911 has barrel hood - breechface contact under any condition it must be out of spec. And the aftward limit of travel of the barrel in the slide cannot reasonably have anything to do with lug contact simply because according to the blueprints there's a gap of about 0.020" between the lugs, as shown here (again):

PICTURE 404

So if it's the lugs that won't let the barrel go back any farther (let alone the chamber face & guide blocks) where's the error in the blueprints? Or is that gun just out of spec?

[Edited: All I'm really saying is if that if a 1" spec'd peg doesn't fit in a 2" spec'd hole - something's out of spec.]

Quote:
...if the gauge wouldn't slip between the breechface and barrel face... I had the option of offering less money or leaving it there.

I am a little confused... gap between the hood and breechface or guide blocks and barrel face? (hood -n- breachface means the barrel is sitting on the guide blocks)

I don't pretend to have examined enough 1911's to have noted the extractor contact with the chamber face. But battering of the chamber face and/or the extractor head would certainly get my attention. Dan's calculations are thought provoking, since I always assumed that military guns were set up that way - with no breech to hood contact at all. A gunsmith who sends customs to troops in Iraq told me that the ones with breech to hood contact were locking up because of the sand, which is what I would have expected.

I wonder if this photo (from another thread) actually shows the results of extractor contact with the chamber face?

One further comment about the fitting of bullseye type barrels. If you want more than one lug to bear, as seems optimal for bullseye use, the hood has to be cut last, not first. That presents some serious measurement difficulties for most people.

Just one more point of view... Jerry Kuhnhausen's Vol-II page 127 states that the distance from the front (only) face of slide lug 1 to the breechface be equal to to the distance from the back of the barrel hood to the back of barrel lug 1 while eliminating any mis-match on the guide blocks.

Apparently Kuhnhausen wants all three surfaces (4 if you count the extractor hole) to contact simultaneously for "Custom Built Pistols" OR I didn't understand what I read.

I decided to use the OEM Metroarms barrel because I was able to distribute the barrel contact across the guide blocks, maintain a .003-.005 gap between the hood and breechface and still have some headspace left over. Also, all three barrel lugs contact slide lugs... win.... win... win...

All is good and what a great learning experience this has been.

I would like to thank everyone for such a broad range of perspectives that help paint a clear picture of the differences between a military weapon and and bullseye shooter.

You all are makin my lil head hurt again here.

When I began putting my gun together I noticed the barrel fit early on so, over a period of days, I began removing the tiniest bits of metal until I ended up with no contact between the barrel hood and the slide (in battery on a chambered round). I can only just barely slip a piece of notebook paper between the hood/slide and inner slide block/chamber face points.

My barrel floats in the back and the chambered round fits tight while I can still spin it from underneath with the slide off of the gun.

I think what really happens here is that the round entering the chamber begins the barrels forward motion. After a certain point, the upper barrel lugs will pull the barrel into battery. Head spacing is a critical factor here right? Tough thing to balance out without good measurements. If the barrel throating is too shallow, the slide can rest on the chambered round and that would be bad.

Too short a barrel hood means that fire can come up through there. Large primers are powerful. Longer barrel hoods, I think anyway, aren't as important as wider hoods for accuracy/lockup and could even be hard on the breechface. This is maybe what was meant before by "wagging the tail"?

A longer hood also means that the barrel throating depth is again in question.

To answer Eric's original question, the barrel stops the slide from flying off of the gun. The barrel lugs, upper and lower do the locking up part, not the breechface. What happens on the way there is different from weapon to weapon and even a different mag or bullet can change that.

I posted this because I didn't see anyone mention the bullets influence in the earlier posts. I've also seen a barrel swapped out that had a narrow hood which left side to side play in the slide/barrel fit.

Quote:
I think what really happens here is that the round entering the chamber begins the barrels forward motion.

That is correct. If the barrel happens to be on the bed and back against the VIS the link will be (or at least it should be) loose. The round being chambered will initially move the barrel forward some short distance until the link goes into compression. When the link goes into compression, the barrel's forward motion will usually stop until the round is fully chambered. After fully chambering the round the slide finally makes contact with the aft end of the barrel (hood and/or chamber face) and begins to push the barrel forward and also cause it rise up off the bed due to link action. The barrel is both pushed and raised into battery by the slide and the link.

Quote:
After a certain point, the upper barrel lugs will pull the barrel into battery.

No. All the upper barrel lugs (the radial locking lugs) do is get engaged or mesh with those of the slide when the barrel's pushed forward and up into battery by the slide and link. They don't pull anything. [Edited: They just sit on top of the barrel and go along for the ride. The only time they do anything at all is after firing: in a mid-spec Gov't Model they make contact with the slide lugs after the bullet pulls the barrel forward in the slide about 0.012" (see my previous pic) and then pressure locks the slide & barrel together until the bullet leaves the barrel.]

Quote:
I posted this because I didn't see anyone mention the bullets influence in the earlier posts. I've also seen a barrel swapped out that had a narrow hood which left side to side play in the slide/barrel fit.

Hello and all good points.

I tried to say that I learned that dirt/grit tolerant military 1911s require the barrel/slide return to battery be stopped by the guide blocks and need a hood/breechface clearnace whereas a bullseye shooter can achieve better barrel control using the barrel hood fit to control return to battery.

I did have a blurb about headspace which speaks to actually chambering a round.

I choose the Metroarms barrel because it allows the guide blocks to control battery lockup while I still have some clearance between the hood and breach face for dirt and grime. I choose this combination because I am not building a target pistol but rather a range beater.

My Kart barrel was money well spent on education and the Colt barrel is still available for future use.

Quote:
...dirt/grit tolerant military 1911s require the barrel/slide return to battery be stopped by the guide blocks and need a hood/breechface clearnace...

I've heard that reason given a lot, but I'm not so sure it has any merit. If you need some clearance for dirt between the hood & breechface so the gun will keep working, wouldn't you also need some clearance between the chamber face & guide blocks so the gun will keep working?

But that's a dumb idea (my specialty) cuz you can't have a clearance in both places - the slide'll just move forward until one (opr both) clearance is closed.

So why would the hood need the gap and not the chamber face?

Could it be they shot a gun of each type in the dirt to find out? Or is dirt behind the hood just easier to see? Or.......

Niemi, don't you usually have some "clearance" between both barrel and slide in the form of fore/aft movement in battery? I don't know why extra clearance at the hood would be preferable, though.

Quote:
The round being chambered will initially move the barrel forward some short distance until the link goes into compression. When the link goes into compression, the barrel's forward motion will usually stop until the round is fully chambered.

I got ole franky out to see what's going on and I'm seeing something like this but it's not only the link doing it. What I see is the barrel hood being pushed up against the upper slide lugs. After this, the round begins to fully chamber. The link can't move anywhere until the slide passes the taper on the front of the hood.

Quote:
After fully chambering the round the slide finally makes contact with the aft end of the barrel (hood and/or chamber face) and begins to push the barrel forward and also cause it rise up off the bed due to link action. The barrel is both pushed and raised into battery by the slide and the link.

The only thing I wonder about here is the timing. Is the round fully chambered before the gun is in battery or is it simultaneous? Depends on a few things I think. I'd say that it's different from weapon to weapon. It would make a difference on what is actually pushing the barrel forward right? On my gun it's a photo finish. The barrels taper is is at the final quarter inch or so worth of motion before the slide should contact the barrel hood. It makes me wonder about the upper lugs because I have a substantial amount of engagement. As I recall, it's near .050 and maybe a touch more. In fact, if I slowly release my slide into battery (empty chamber), I can see the barrel move before the hood makes contact.

Quote:
I've heard that reason given a lot, but I'm not so sure it has any merit.

The gap between the barrel hood and breechface provides clearance for other interfaces to get dirty. More specifically, as the barrel to guide block gap becomes contaminated with dirt and grime the hood to breechface gap shrinks. Hood to breechface gap provieds room to grow.

Quote:
...don't you usually have some "clearance" between both barrel and slide in the form of fore/aft movement in battery?

Yes. When only the barrel and bushing are installed in the slide, blueprint info for the M1911A1 says the barrel's fore-aft play in the slide can range from 0.005" to 0.020". That's the 0.0125 ± 0.0075 inch shown on the drawing in Post #27.

FWIW, when I put the original GI barrel back in Petunia's Remington Rand slide it has 0.005" of fore-aft play. The usual hard-fit "NM" barrel will have little (if any) fore-aft play because after the locking lugs are equalized, the extra-long hood is trimmed to just barely allow the barrel to go up into the slide.

Quote:
What I see is the barrel hood being pushed up against the upper slide lugs. After this, the round begins to fully chamber.

First, we need to get our terminology squared away. The barrel's hood (aka, extension) is the little tab on the very aft end as shown here:

Not sure if that part of the barrel you're talking about has a specific name. Anyway, it'll get moved up when doing it slowly by hand. Maybe I mis-spoke: it may do the same when feeding at speed - maybe not.

Quote:
The link can't move anywhere until the slide passes the taper on the front of the hood.

Not sure what you mean by this.

Quote:
Is the round fully chambered before the gun is in battery or is it simultaneous?

The round has to be fully chambered before the slide can exert any force directly on the barrel, so the round ends up getting fully chambered just as the barrel starts to get linked up by the slide.

Quote:
The gap between the barrel hood and breechface provides clearance for other interfaces to get dirty. More specifically, as the barrel to guide block gap becomes contaminated with dirt and grime the hood to breechface gap shrinks. Hood to breechface gap provieds room to grow.

But when that interface is the chamber face & guide blocks, as they get crudded up - the gap between the hood & breecface gets larger!

It's the gap between the locking lug surfaces that shrinks when dirt at the back end causes the barrel to move forward in the slide (see previous post).

Quote:
But when that interface is the chamber face & guide blocks, as they get crudded up - the gap between the hood & breecface gets larger!

It's the gap between the locking lug surfaces that shrinks when dirt at the back end causes the barrel to move forward in the slide (see previous post).

Hello... OOPS... thats what I meant to say

It just dawned on me why different people report seeing different barrel gaps... in-spec made 1911s will have a gap between the hood and breechface and these people claim this arrangement is dirt tolerant, as it should be. Whereas, custom hard fit barrels are mostly fit by gun smiths who use the barrel hood to control lockup but this custom variation, being so tight, is more prone to dirt/grime contamination because its made so tightly.

Please excuse my "slowness" to understand this basic principle.

Before we accept the theory/ opinion, that tolerances large enough to throw a cat through are necessary for realibility, let's take a look at modern high pressure pistols. Pistols designed for fighting/defense. These pistols exhibit hard contact between the hood, breechface, and other locking surfaces...100s of thousands of these pistols, have replaced the 1911, and are in use by law enforcement, and military officers, aorund the clock, the world over. In my 30 years as a an L/E firearms instructor/armorer for an 800 officer department, close tolerance / precision fit was never a detriment to the reliability of those weapons... John Browning did not have the luxury of todays computer controlled manufacturing processes . As I said in an earlier post, blueprints eventually become an amicable agreement between the designer and manufacturer(s), to facillitate production, hence the generous early 1900 tolerances.

Don't modern autoloading pistols use a locked breech short-recoil method pioneered by John Browning that only use one big locking lug and the barrel hood to position the barrel in the slide?

Comparing a Sig P226 to a 1911 is an apples to oranges comarison IMHO.

My Sig P226 and Walther PPS are both good example of the more modern design. I compare the P226 to the 1911 below:

I was interested in whether the P226 used all hood contact and it does. Here is a picture that shows light shining though a gap between the P226 guide blocks and barrel face.

Have you folks seen Wilson's 9mm Spec-Ops 9, and it's barrel-slide setup?

Good call. It looks like the Spec-Ops 9 is a linked version of the P226 style (single lug) barrel:

Many of the newer designs have barrels with just the one upper lug. Sigs, glocks, etc. Elimination of the link is the most significant change, not the upper lug. In my opinion the switch to one lug does not imply simpler=better. Manufacturing and assembling a one-lug barrel is just quicker than the complex process of fitting a 3-lug barrel. Presumably, 90 percent or more 1911 barrels have only one lug in bearing anyway. Speedy fit drop-in barrels were never intended to bear on more than one lug. It works ok for most purposes. But the original design allows for a much better fit if you want to spend the time to get it. The Hi-Power still has a 3 lug barrel, so JMB did not have a change of heart on the benefits of his original idea.

I don't pretend to have anywhere near your experience, however I have to question a couple of statements that you make above. There is no doubt that manufacturing techniques influence the end product. But the fact that JMB did not have CNC equipment at his disposal does not mean that early production was a regrettable compromise with the original design. If in fact the loose tolerances on early military guns were a result of manufacturing limitations, then by the same logic, we would now have consistently high quality and reliable products right off the shelf. Yet, it is not so.

We all know that a correctly fit 1911 or any gun for that matter requires human hands and skill that cannot be duplicated with a machine. Early production pieces actually had those skilled hands available to fit and adjust as needed.

I'll go out on a limb and speculate that the generous early (i.e. early 1900's) tolerances were a whole lot closer to what JMB had in mind, rather than simply reflecting manufacturing compromises. CNC equipment can produce tolerances of around .0005", but nothing I've seen on the market even comes close to that level of perfection. I think the bottom line on that subject is that nobody bothers with original design specs in the first place.

Finally, I'd like to comment on the use of hard fit close tolerance weapons in L/E. To me, those terms describe a precision bullseye pistol, rather than a reliable life-saving tool. You are saying in effect that you can have both at the same time, while I, in my ignorance, say that it can't be so. I have nothing against a beautiful precision masterpiece and I admire the folks like yourself who can build them. But it has become clear to me that a self defense pistol is a different animal. I own both types, and I know which one I prefer to carry.

I guess I'm still foggy on what the disadvantage of guide block contact is. Assuming the extractor is short enough not to peen the barrel, what is the downside?

From "America's Munitions 1917-1918" by Benedict Crowell, The Assistant Secretary of War, Director of Munitions, Government Printing Office, 1919:

"In December, 1917, the Remington Arms-Union Metallic Cartridge Co. was instructed to prepare for the manufacture of 150,000 automatics, Colt Model 1911, at a rate to reach a maximum production of 3,000 per day. Considerable difficulty was experienced in obtaining the necessary drawings and designs, because the manufacture of these pistols at the Colt Co. plant had been largely in the hands of expert veteran mechanics, who knew tricks of fitting and assembly not apparent in the drawings. The result was that the drawings in existence were not completely representative of the pistols. Fnally complete plans were drawn up that covered all the details and gave interchangability between the parts of pistols produced by the Remington Co. and those by the Colt Co., which was the goal sought." (Page 189)

So much for precision manufacture from carefully dimensioned drawings. Chuck Clawson relates a similar challenge in the runup to WWII.

Quote:
I guess I'm still foggy on what the disadvantage of guide block contact is. Assuming the extractor is short enough not to peen the barrel, what is the downside?

I'm not sure there really is any downside for a Gov't Model. But for a NM/hard fit barrel, the choice is easy. There's only one hood but two guide blocks, so trying to hard fit a barrel for zero fore-aft play in the slide (the ultimate Bullseye gun) by fitting two guide blocks against the chamber face would be a nightmare. Lots, lots, lots easier to trim one hood. Plus, the end of the hood's easier to whack on - stickin' right out there, proud as punch!

Another possible advantage to guide block contact that I've not seen mentioned is the greater surface area of the blocks might provide longer wear. Maybe.

Or were you asking something else?

Quote:
Or were you asking something else?

No, I meant just what I said. Tuner and JK seemed to agree that there shouldn't be any guide block contact, and I'm just eager to know why not, other than the extractor peening problem.

IIRC, Tuner's said more than once he likes to have about 0.003" of clearance between the hood & breechface - so that means guide block contact. But Tuner's also said he doesn't build Bulleye guns.

Maybe JK's talking about no guide block contact (meaning hood contact) somewhere in his Optimum Performance (Bullseye, etc.) 1911 section?

Quote:
No, I meant just what I said. Tuner and JK seemed to agree that there shouldn't be any guide block contact, and I'm just eager to know why not, other than the extractor peening problem.

If you are working on Mil Spec GI pistols, you are locked into the original design. If contacting the chamberface is not objectionable to you... then, as Tuner also said, it will usually work. If you are installing aftermarket/match barrels, it is not the best approach.

Quote:
about 0.003" of clearance between the hood & breechface - so that means guide block contact.

Not unless there's something wrong. I've got pistols here that I could cut the hood completely off of the barrel...and there wouldn't be any contact between the blocks and the chamber face when the gun is in battery.

Oops!

Hi Tuner:

Sorry, I forgot my usual caveat: when saying there'd be guide block contact if there wasn't any breechface contact I was referring to a slide and barrel that were both within Ordnance specs.

If there's no contact at either of those places when the gun's in battery and the hood is cut off it means the barrel's aftward position within the slide is limited by contact between the faces of the locking lugs not in contact when the gun's fired, as shown below.

However, those "opposite" lug faces cannot contact each other if the barrel and slide are both within spec:

* If the slide is within spec and as large as possible between lug #1's forward face and guide block (1.312") the barrel must be 0.010" or more below spec because that minimum comparable distance on the barrel is 1.322".

* If the barrel is within spec and as small as possible between the aft side of lug #2 and the chamber face (1.322") the slide must be 0.010 or more above spec because that maximum comparable distance on the slide is 1.312".

That this gun works OK is either a glowing testament to JMB's design or maybe a hint that all this specification malarkey doesn't amount to a hill of beans.

Dan... When the gun is fired, the barrel can't move rearward within the slide. The bullet exerts a forward drag on it... just like a closely fitted hood pushes the barrel as far forward as the horzontal lug engagement will allow. When the gun is static/in battery, the barrel's rearward movement is limited by the slide's lugs... but on the opposite sides from the firing condition. Unless there's a problem with the specs and dimensions with the slide and/or barrel lugs... the guide blocks won't bear against the chamber face.

I check these things by pushing the barrel to its rearward limit within the slide and slipping a .003 feeler gauge between the face and the guide blocks, and only rarely have I found one that won't let the gauge in, and when I do... I usually find a problem with the barrel itself. This, regardless of the hood's proximity to the breechface.

Quote:
I've got pistols here that I could cut the hood completely off of the barrel...and there wouldn't be any contact between the blocks and the chamber face when the gun is in battery.

When you said "...when the gun is in battery." I assumed you meant in battery before the gun was fired.

After firing there will naturally be no contact between the blocks and the chamber face - unless the barrel was perfectly and tightly fitted to the slide for zero gap at the blocks.

But that's a fitted barrel where just about anything is possible. My comments are based on an in-spec USGI (not NM) barrel in an in-spec USGI (not NM) slide. All I'm saying is that if a USGI M1911A1 is lying (laying?) on the bench in battery and there's no contact at either the breechface or the guide block(s) - there's something about either the barrel or the slide (or maybe both) that's out of spec.

I mentioned in a previous post that I didn't want to hack up my Colts or Springfield so I choose to hack up my Metroarms instead.

OK, everyone hold their breath - I leveled the locking lugs on my Metroarm slide a tad bit too much. Now they are .003 below the .159 -.003 = .156 block height.

This is not a big deal because I have plenty of room between the block and extractor and I just ordered another Kart easyfit barrel. I intend to fit this one better that I fit my first attempt. Live and learn. This learning stuff is what it is all about for me.

BTW, I attributed tall and uneven guide blocks to inaccuracies in my first Kart fit. It just took me a while to understand that the guide block were off from the factory... shocker huh.

Looking forward to the next job.

PS. I would like to try to balance all three lugs next time so now I have to find a way to accurately measure hood-lug distances because my digital calipers are only ±.001”

Quote:
Tuner and JK seemed to agree that there shouldn't be any guide block contact, and I'm just eager to know why not, other than the extractor peening problem.

I've got a sneaky feeling it's pretty unusual for an in-spec M1911 to have any extractor nose/chamber face contact & peening at all. That's because the calculated distance from the extractor nose to the guide block is 0.0125 ± 0.0180 inch and that's with the extractor pushed fully forward in the slide. So the extractor nose can protrude in front of its guide block as much as ]0.0125 - 0.0180[ = 0.0055". That 0.0055" is about 15% of the 0.0360" range. If the dimensions of the 3 parts involved are normally (Gaussian bell curve) distributed, the number of guns with the "problem" would be much smaller than 15%, perhaps 1% or less.

And even if an extractor nose did come in contact with the chamber face, it can do so in an in-spec gun only if the extractor is forward in the slide. But that same extractor that sticks out 0.0055" can also move aft at least 0.013" in its tunnel. So when going to battery, the chamber face can push the extractor aft (against the friction with its tunnel) so it's flush with its guide block.

It's not as if the extractor was being held out in front of its guide block by some firm, physical restraint.

Quote:
I have to find a way to accurately measure hood-lug distances

Measuring those distances on the barrel is probably the easy part of the job. To balance (aka, equalize) the barrel lugs you need to know the corresponding distances in the slide between the breechface and each of the 3 lugs.

Those distances in the slide are the difficult ones to measure. Common ways of getting those measurements are with...

* ... a height gauge on a granite surface plate (slide clamped upright at the proper angle), pr...

* ... an adjustable "Lug-Breech Reference Fixture" such as the one illustrated in J.K.'s Vol II, page 128, 2.

At one time I had thought of measuring those distance in the slide using a washer to "bring" the lug surfaces up to the level of the center rail, taking the measurement with calipers...

...but never used it because the measurements just felt too uncertain.

Has anyone successfully tried marking the barrel lugs with Dykem layout fluid and stoning off the contact points until all three lugs contact?

That would require you to cut the hood loose enough to get the barrel into the slide, precluding a tight hood lockup.

WOW... that was a little too obvious. I think I must have left my brain at the front door when I came in.

Hm-m-m-m.....DING! Howzabout this for a goofy barrel fitting sequence:

1. Cut the hood short so the barrel will drop into the slide
2. Use Egumpher's Dykem method to equalize the lugs (no measurements need to be taken)
3. Weld up the hood
4. Trim the hood so the barrel just baaaarely squeaks into place
5. Shoot some +P ammunition
6. Repeat steps 3 & 4, if necessary

There... I warned ya it was gonna be goofy!

Pros? Cons?

Sounds plausible to me. I considered welding up my existing Kart barrel in a similar fashion but sold my welder ten years ago.

If I can find a competent welder/gunner here in the Tampa area I can certainly give this method a try

Since I already have great shooters I mostly want to learn and this seems to be a good candidate to help with the 1911 cause.

Quote:
That would require you to cut the hood loose enough to get the barrel into the slide, precluding a tight hood lockup.

Well... not so, it is done regularly by those who can... you need a "very" accurate method of measurement.. and an equally accurate method to cut the barrel lug shoulders.

The first slide lug is reference zero, and the first lug on the barrrel is reference zero... the remaining two barrel lugs are then adjusted accordingly.

Then as Neimi stated earlier, the final adjustment is the hood length... contact fit to the breechface.

Don't get the idea I've tried that method - I haven't. It was just something triggered by RobL's post (thanx RobL). But others have no doubt thought of it and tried it before.

And while I know nothing about welding, I do know USGI barrel hoods and lower lugs got welded up for tight fitting back in the olden days. Remember hearing the barrels were poked into a bucket of wet sand - as a heatsink.

If all three lugs manage to get in contact the +P ammunition might not be necessary.