Barrel movement in battery...

[Involute]

I know how the barrel and slide should lock up tight in battery when everything is fitted properly. I'm trying to figure out, though, if the barrel can be pushed down slightly, is that a problem that I should concerned about? I have two 1911's that do this. If it's just an accuracy thing, then I don't really mind, but if it's going to lead to excessive wear or failure - I'd like to fix it. I'm just not sure of the nature of the problem.

[jaybo292]

Welcome to the forum.I`m sure one of the more knowlegable members will help you out.

Jay

[wichaka]

Welcome to the forum!

Most do have a little give when you push down on them when in battery. If it's excessive, more than a few thicknesses of paper.......then it should be looked at.

[scooter]

IF the chamber is empty it will move slightly,but neither my commander nor my eclipse will move with a round chambered.I would test that too.

[CWG]

IF the chamber is empty it will move slightly,but neither my commander nor my eclipse will move with a round chambered.I would test that too.

Carefully We have a guy at the range, his nickname is fingers, which is kinda odd, considering the lack of plurality on one hand :D

[1911Tuner]

Although that type of play indicates an incorrect barrel fit, it mainly only affects accuracy because of inconsistent repositioning of the barrel from cycle to cycle. More important to the well-being of the gun is the depth of lug engagement.

The barrel is cammed upward as far as the radius in the lug and the crosspin will allow due to the way the crosspin forces the radius to climb up on it for the last few thousandths of an inch. That you can push the barrel downward a little is good indication that this is working as it should. It's a sort of built-in
method to take up the slack when the fit isn't perfect so that the barrel won't self-destruct in a thousand rounds. (Another one of those "little things"
that isn't readily apparent until you really study the design. Was ol' JMB a sharp cookie, or what?)

As long as the lugs engage to full depth, or nearly so, they won't suffer setback deformation as readily as they would if the lugs were only engaging to half their depth without the extra "boost" provided by the lug and pin geometry.

The only way to correct it is to either weld up the lower lug and refit...weld the slots between locking lugs and refit (or both)...or to replace the barrel with one that's a little oversized in the right places, and hand fit.

As Wichaka noted...If the drop is more than about .005 inch, it should be checked out or barrel lug life will suffer.

[Involute]

Thanks everyone! I was looking over (safety checking-n-stuff) a S70 Combat Government Model when I happened to first notice the movement and wasn't sure what to make of it at the time. So, I went home and checked my own GM's. My 1911A1 moves only slightly, maybe .001-.002. The 1991A1 ORM moves a bit more, even with a round chambered. I'll have to throw a test indicator on it and see how much. I'll also check the lug engagement. My others don't budge when they're in battery.

Gonna have to go back for a second look at the CGM.

[1911Tuner]

Thre were a lot of pistols that Colt threw together in the 70s that could have been helluva lot better, and many did have an excess of barrel drop from in-battery. If yours follows suit, I'd say that the barrel is standing on the link.
A sign that the lower lug may be out of spec...or it could be the dimension from the bottom of the lug slots in the slide relative to the slidestop crosspin centerline. It didn't really hurt anything in the short term...as in the amount of use that the average buyer would put the gun to...but if the gun is shot hard, it'll start to take its toll if the play is excessive. Vertical stringing on target is one symptom. Lug setback in the upper half is the longer term issue. Keep an eye on that. As the lugs deform, the barrel and slide gain a larger and larger gap between'em...Endplay/Endshake...Headspace opens up by the amount of setback...and it's in the case rupture direction.

[Involute]

I measured the lug engagement with the barrel all the way down at .041". The total barrel movement is about .015". I also checked to see if it was standing on the link, but it doesn't appear to be. The link hole is large enough that when the pin is pressed tight against the lower lugs, the link still moves freely.

[1911Tuner]

Involute...Measure vertical lug engagement like so:

Whittle a popsicle stick down to fit the breechface. Make sure it's well clear at the sides. SLip it between the hood and slide and let the slide snap to battery from about halfway back. Measure from the top of the slide to the top of the hood. Remove the stick and repeat. The difference is the depth of vertical engagement. If it still comes to .041 inch, you've got about 82-83% depending on lug height. I'd set that as a bare minimum for a gun that you'll shoot as much as 500 rounds a year....and less use would be better. .045 inch, or about 90% is a minimum for a hard-use gun. I'd much rather see 95-98%.

[ArmscorBA]

1911 Tuner,
You are the man! :D
Ivan

[1911Tuner]

1911 Tuner,
You are the man! :D
Ivan

Nah. But I did stay at a Holiday Inn Express last night... :D

[Involute]

Hi Johnny-
Thanks for all the great information!

I measured as you suggested and came up with .042".

Just out of curiosity I measured a few others, also.
1943 1911A1 - .043"
WWI Repro - .050"

[1911Tuner]

Hi Johnny-
Thanks for all the great information!

I measured as you suggested and came up with .042".

Just out of curiosity I measured a few others, also.
1943 1911A1 - .043"
WWI Repro - .050"

Okay! .042 is a little short of the mark, but if at least two lugs are taking the brunt of recoil...or if the #1 lug is handling it alone...the gun is at least serviceable as a carry gun and occasional shooter, as long as you get a consistent .042 depth on each return to battery. This should be checked with ammo...dummies if you can arrange'em...live if you're extremely careful. Top off a mag and run each one through at full speed...and check the dimension to see if it varies. Rule of thumb...Actual depth X 2 gets you close to the total percentage of engagement. Nominal lug height being .050 inch,
+/- .002 or thereabouts. So, .042 is close enough to 84-85% to go ahead and call it that. A good many pistols have done pretty well with 80.

The '43 USGI...about par. The Army wasn't too concerned with barrel OR slide life, since they had a blue million in stock.

The WW1 repro is excellent at about 100% engagement. Question is...How much endshake is there, and which lug or lugs is/are taking the load?

[Dustoff '68]

My barrel doesn't budge at all on my SA Mil-specs....is that a problem?

[Involute]

I guess I should clarify...
The .042" measurement was done while pushing down on the barrel. When I cycled a mag full through, the natural RTB position gave .050" engagement consistently +/-.001". Same for the USGI.

End play - total min/max feeler
1991A1 - .012" .006/.018
USGI - .010" .002/.012
WWI Repro - .009" .002/.011

I'll have to get back to you on which lugs are taking the load - that'll take a little more time.

[1911Tuner]

Dustoff...No problem. That's as it should be.

Involute...Very good. You may not have quite the issue that you thought. The accuracy may not be exactly sterling, but there shouldn't be any lug damage through normal use.


Now, let's see which lug(s) takes the force of recoil, and how much endshake is present. Both these factors are important to long barrel lug life.

Clean all oil or solvent from the slide lugs and slots.

Use a sharpie marker or layout fluid to color the front faces of all three barrel lugs and shoot the gun a few times. Two magfuls should do. Look at the lugs
to see which ones haven't been touched. The ones that look different...color may be burnihsed, or even completely removed...is/are engaging when the gun fires. If it's only the #1 lug, you've got a pretty good lockup. If it's the other two...ditto. If it's #1 and either one of the others...double ditto.
If it's only one of the other...# 2 or 3...you'll need to limit the firing of any +p
ammo and forget about a Super or Rowland conversion, and you probably should limit standard hardball or its equivalent to about 2500-3,000 rounds a year.

If all three are bearing...equalized...you've got the strongest lockup that your gun will provide. You should also play the lottery, because you've been smiled upon by the great spirit of chance.

Now...on to the endplay...the final part of the lockup equation. We'll move on to working headspace later. Cut some strips of typing or printer paper that will fit the breechface from the top. Ease the gun into battery on one..then two...then three, etc. and pull the strip straight up until you get the required number of strips that force you to tear them in order to get'em pulled out. Multiply the number of strips by .004 inch...the average thickness of each strip. That will provide the amount of endplay that exists between barrel and slide lugs. Less is better. Excessive endplay...endshake...affects
not only how far the breech will open when the gun fires...it also determines
how much of a running start that the lugs have at each other before engaging and locking. The harder they "slap", the faster the lugs will deform and set back, and the faster that the working headspace will increase.

Some of the endplay will be taken up when a round chambers due to the barrel being pushed a little further forward by the cartridge, and though it isn't held tightly forward, it does help a little in reducing the distance. This will reduce the slap by about .003-005 inch on average. Enough, as long as the amount of static endplay...empty chamber...isn't more than about .010-.012 inch. Many factory guns that I've checked run as much as .015 inch and do okay under normal use. The ones that have more than that suffer early lug deformation. How early is determined by the vertical engagement and how many lugs are taking the load.

Ideal is full depth...All three lugs in equal engagement...With .005 inch or less
endplay. Only rarely do we get an ideal with ordnance-spec factory guns until we get into the high-end semi-customs..and even then it's not typical.
Even the Les Baers, known for tight barrel fit...usually don't have fully equalized lugs. That's usually available only with hand-fitted barrels, and usually then only if specifically requested. On these, you'll shoot the bores completely slick before you'll deform the lugs to any practical degree with reasonable ammo pressure levels. These are the ones for the hot-rod conversions. The Super and Rowland will beat the lugs out of the average
ordnance-spec pistols in short order.

For the record...Barrel lockup is a misleading term. "Locked Breech" doesn't occur until the gun is fired. Prior to that, the barrel is simply held in battery by whatever interference is present at the lower lug to slidestop pin fit/top lug to lug slot fit...(vertical)...hood to slide fit/barrel lug front face to slide lug rear face...and the static force of the recoil spring...(Horizontal)...and is not technically "locked." Simply stated...The gun locks under pressure, and unlocks when the bullet exits and pressure drops.

[Rocket 6R]

Involute...Measure vertical lug engagement like so:

Whittle a popsicle stick down to fit the breechface. Make sure it's well clear at the sides. SLip it between the hood and slide and let the slide snap to battery from about halfway back. Measure from the top of the slide to the top of the hood. Remove the stick and repeat. The difference is the depth of vertical engagement. If it still comes to .041 inch, you've got about 82-83% depending on lug height. I'd set that as a bare minimum for a gun that you'll shoot as much as 500 rounds a year....and less use would be better. .045 inch, or about 90% is a minimum for a hard-use gun. I'd much rather see 95-98%.

Tuner, I'm trying to conduct this test on my two Gov't models and don't understand how to get a reading. If I measure from the top of the slide to the top of the hood I get a reading of .109". I don't understand the purpose of the popsicle method. Can you please help me understand your method?

Thanks, Rocket 6R

[1911Tuner]

Surely!

I probably should have said Chamber instead of Hood. Haste will be my downfall one day...

The popsicle stick lets the slide push the barrel as far forward and up as it can go, but prevents the lugs from engaging. Instead, the top of the chamber...which is flush with the tops of the lugs...stops against the underside of the first slide lug. Now, you've found the topmost point of the lug. Removing the stick lets the lugs engage to the full depth that your particular gun will provide. Subtracting the difference gives you the amount of upward travel of the barrel, and the depth of the lug engagement.

Be sure to take the measurement at the front of the ejection port.

[Rocket 6R]

Thanks Tuner, I understand now!

I measured my Pre-70's Colt (1956) and it came to about .041", which has countless thousands of rounds through it.

I also measured my Colt XSE Gov't and it came to .047", which has about 600 rounds through it.

I found it a little hard to get exact measurements, too much wobble on the caliper.

Thanks, Rocket 6R

[1911Tuner]

Thanks Tuner, I understand now!

I measured my Pre-70's Colt (1956) and it came to about .041", which has countless thousands of rounds through it.
I found it a little hard to get exact measurements, too much wobble on the caliper.

Thanks, Rocket 6R

Measure three times and take an average. That'll get it a little closer until ya get the hang of it. .041 inch is about 82% which is about low-end par for an ordnance-spec gun. With thousands of rounds through it without undue lug setback, you musta got lucky and drew one that had two or more bearing the load. Might wanna check your headspace anyway, just to be on the safe side.

.047 is high-end average for ordnance spec. Double kudos if there's more than one in the game...Triple kudos if one of'em is the first lug.

[Involute]

Alright. I did the endplay check. The results are...

1991A1 ORM - 3 sheets - .012
'43 USGI - 2 sheets - .008
WWI Repro - 1 sheet - .004

It may take a day or two to get the results of the lug contact.

Thanks! This is some great information!

[Rocket 6R]

Measure three times and take an average. That'll get it a little closer until ya get the hang of it. .041 inch is about 82% which is about low-end par for an ordnance-spec gun. With thousands of rounds through it without undue lug setback, you musta got lucky and drew one that had two or more bearing the load. Might wanna check your headspace anyway, just to be on the safe side.

.047 is high-end average for ordnance spec. Double kudos if there's more than one in the game...Triple kudos if one of'em is the first lug.

I checked the end-play on the old Colt and it measures .019" while my Colt XSE measures .013". I also checked the headspace on the old Colt and it measured .904". According to Jerry Kuhnhausen's book, that headspace falls in spec. I think I'm good to go on the old Colt but the end-play I think, according to your teachings, it a bit much. Also the when pressing down on the barrel, when in battery, moves downward .007" of an inch and stays there. The .007" measurement is taken from the front of the chamber area. I don't have any vertical stringing when firing the pistol. However, the best I can shoot the gun off a bench is 5" at 25 yards as opposed to shooting 2.25" groups with my Colt XSE model. One thing that does not help is that the barrel is pitted and the rifling is very shallow.

Thanks, Rocket 6R

[1911Tuner]

Alright. I did the endplay check. The results are...

1991A1 ORM - 3 sheets - .012
'43 USGI - 2 sheets - .008
WWI Repro - 1 sheet - .004

It may take a day or two to get the results of the lug contact.

Thanks! This is some great information!


ORM 91A1...High average. Still not bad for a gun that's probably been shot
some. Most new/unfired examples I've checked run about .008-.010 inch.

'43 USGI...Average, and actually very good for an "Old Girl." Likely arsenal rebarrelled, and good attention to detail by the armorer. (Wonder if it was me?) ;)

WW1 repro...Wow! Maybe there's more to the WW1 repros than just appearances. :cool:

When a round is chambered, the barrel is usually set forward a little, and reduce some of the slap...usually about .004-.005 inch, depending on the ammo.
****************

Rocket...

Yeah. .019 inch is a little excessive. I'd limit the +p stuff to function check and carry. "Soft" handloads will also go a long way toward preserving the lugs. Since your static headspace is that good, you can help a lot by using cast lead bullets with a shoulder, and seating the rounds just a little farther out. The bullet shoulder will bear on the chamber shoulder and give it a little forward push to minimize the slap-seating. Just be sure the OAL that you use
will allow smooth chambering.

.013 on the XSE is high average, but if the headspace is good, chambering a round will reduce it a little by holding the barrel forward. The .007 drop is not a major concern because the lug to pin geometry will hold the barrel up high enough to get the depth to its full potential...for that particular gun. When it fires, the lugs will engage and hold it there. As long as the vertical engagement is in the 85% range, you should be good to go unless you shoot like I do...in excess of 50,000 rounds a year.

[Involute]

I'm back again 1911Tuner. Shot two mags out of each gun.
1991A1 ORM is contacting on lug #2 only.
WWI Repro is contacting heavily on lug #1 and #2, it's just barely marking #3.
'43 USGI is contacting heavily on #1 and #3, it's partially contacting #2. Upon futher investigation it appears that there was a slip in the lug cutting operation on the slide. About 60% of lug #2 has about a 15 degree bevel almost to the full lug depth on the left side of the lug. The remaining 40% actually has good contact, just like #1 & #3.

I don't think the USGI has been shot enough to make it worth an arsenal rebuild/rebarrel. There are alot of machine marks where I would expect to see some amount wear.

There have been some great tips in this thread. Thanks Tuner! Now I have alot more things to look at when buying a used gun, also.

[1911Tuner]

1991A1 ORM is contacting on lug #2 only.

Typical.
***********



WWI Repro is contacting heavily on lug #1 and #2, it's just barely marking #3.

Wow! Let us hope that yours is representative of the breed.
*****************


'43 USGI is contacting heavily on #1 and #3, it's partially contacting #2.

Also typical of the GI pistols. There was usually two lugs bearing and one close behind, and eventually all three would come to bear with use. The beveled lug...I dunno. I'd have to see it before I could take a WAG at the reason for that.
****************

Just for the record...The lugs are numbered from back to front. #3 is the one closest to the muzzle. I think I mentioned it, but just wanted to clarify.

[Involute]

Hi Johnny,

In case you're interested in more data...

My other WWI Repro, which was slated to become my new carry gun, measures as follows...
Lug contact on #1 & #2.
Lug engagement - .041", I couldn't believe it so I measured 3 times - didn't change :(
Endplay - 2 strips .008"

The barrel doesn't budge in battery, though. I guess that you never can tell what you've got 'til you check it!

I'm hearing these words that were passed along by a wise pistolsmith...
"I only know what I can measure" :D

Thanks for the lesson!

[1911Tuner]

Okay...Let's look at the big picture.

.041 inch vertical equals about 82% or so, depending on how tall the barrel lugs are. Not ideal, but that's mitigated a little by the fact that two lugs are
in the game...AND...one of those is the strongest one.

.008 inch endshake is decent. Again, not ideal, but not nearly as bad as many that I've seen...and carried. By the time the gun is in battery with a live round, a good part of that slack will be taken out, if not almost all of it, depending on the location of the chamber stop shoulder and headspace.
Less slap means longer lug life.

I'd limit shooting to mostly standard pressure ammo...Hardball...and use the hotter +p stuff for carry, beyond the number of rounds required to insure reliability. I also would advise against heavy use with hardball...and by heavy use, I mean 8 or 10 thousand rounds per year. Note that to me, heavy use means upward of 50,000 rounds and beyond...but I'm not really typical, and I split my range useage about evenly amongst 3 or 4 pistols. Best educated
recommendation is 500 rounds per month, max...and the gun should do very nicely for a long time.

Tip:

A drop or two of a fairly viscious oil in the slide lugs about every 200 rounds will go a long way toward reducing impact and preserving lug life. I use plain old Mil-Spec LSA, available at your friendly neighborhood Army-Navy/Surplus store...or at gunshows...
for about 5 bucks a bottle. Skake well before use.

[warmrain]

Johnny,

We are so da##rn fortunate to have your input here and the patience to take with us. I can't believe this, but it's all starting to make sense and the initial reason I fell in love with the 1911 (JMB's brilliance) is continually reborn when I learn more, through you, about the design.

Thanks for helping me through some stressful times...!

Reading this was a great learning and reinforcing of what you've already taught me. Thanks for the details!

[1911Tuner]

Hey John! About that raise!

:D

Thanks for the good words, warmrain. The 1911/A1 is a study in simple complexity, and understanding how it works is the first step in knowing what to do about one that doesn't meet expectations. The fact that I'm anal over reliability...coupled with an obsessive drive to understand the designer's mind...has made that almost my sole work on these pistols instead of focusing on the (somewhat) more financially rewarding custom scene.

Although I haven't actually been employed as a "professional" gunsmith in over 15 years, I keep my hand in it by beatin' the kinks out of non-functional and/or unreliable pistols for the guys who are about to give up on the design.

A matter of honor, almost. I'm tired of hearing about how "inherently unreliable" the 1911 is, that I just about have to prove'em wrong, and take no small measure of satisfaction and delight in doing just that. The look on a man's face when his pistol just won't quit, after having been nothin' but a headache from day one is worth it.

Incidentally...Now maybe ya'll can better understand why I'm so quick to advise against swappin' out a recoil spring and jumpin' into the Drop-in .45 Super scene. It's a quick way to beat an otherwise serviceable pistol to death. Ask-me-how-I-know! :D (No...I didn't try one.) ;)

[warmrain]

I cringe whenever I hear someone advise a heavier recoil spring to solve a problem...
I for one think you need a 50% raise, what IS 50% of nothin' anyway...

[1911Tuner]

I cringe whenever I hear someone advise a heavier recoil spring to solve a problem...
I for one think you need a 50% raise, what IS 50% of nothin' anyway...

The problem with the Super and Rowland conversions isn't the heavy recoil springs as much as it is the increased stress on the barrel and slide lugs. The guys who do the conversions are under the impression that all they need to do is stick a 24-pound spring in the gun and they're good to go, and they wonder what happened when they start to see cases bulged to to point of rupture shortly afterward..sometimes with as little as 50-100 rounds of that stuff, and by the time they realoze that somethin's wrong, the damage is done, and the gun isn't even safe to shoot with hardball. If they're lucky, the damage is to the barrel only. If they're not so lucky...they're lookin' at a
whole new top-end. To date, I've had three of these on the bench. The owners of two got lucky. One didn't...and the rupture into the magwell bulged the magazine so badly that I literally had to beat it out. The frame was okay. The top-end was history.