Norc 1911 Barrel Lugs Question to Tuner

[combatantr2]

hello;

i know you have discussed this lenghthily in the past but one thread caught my eye started by farscott regarding the barrel lugs of his used norinco 1911. i have a new standard norinco 1911/45acp coming by the end of the week (actually my 2nd the first one was the np27 commander 45acP w/c i sold for money issues) and i was wondering if i can tell from the new looks of it if the new pistol will develop barrel lugs/headspace problems in the future 'say after 1000 rounds or so.

sadly i never bothered to check my first norinco for any barrel lug wear. the gun was flawless thru 600 rounds of factory and reload ammo.

with the new one all i know is that the pistol will be subjected to 3 to 5 shots fired for ballistics i.d. before i can finally claim come weekend. this headspace issue on 1911s continue to muddle up my understanding. and lastly are headspace problems only prevalent with the norinco?

thanks in advance and more power to you.

(others feel free to chime in.) thanks also.

 

[1911Tuner]

Norinco

Hey Combatant,

First, an understanding of how the 1911s locked breech works will help.
When the round fires, the slide and bullet are propelled in opposite directions.
When the thrust faces of the locking lugs are forced together by this opposite
movement, the breech locks. The barrel lugs' front faces and the slide lugs' rear faces are the thrust surfaces that engage under pressure.

As you probably know, I got into ferreting out all the Norinco owners that I could find in about a 6-county area...and even got a few from Tennessee.
I found that a small percentage had barrel fit problems that resulted in damaged lugs and excessive headspace that resulted from that damage and deformation. All the Norincos that I saw had headspace that was a little
looser than I'm comfortable with, along with a lot of fore/aft barrel play within the slide...which can contribute to early lug deformation and increased headspace.

Maybe if I define what headspace is just a little differently...and how it can go wrong in a 1911 pistol, you'll know what to keep an eye peeled for. Headspace can be defined in two ways, and it can be excessive in two ways.
One of which is dangerous, and the other only causes erratic ignition and possible innacuracy.

Static Headspace is the distance from the breechface to the chamber stop shoulder with the gun in battery. Static headspace is what it is, and is constant until lug deformation causes it to change. When that occurs,
the breech will open slightly when the gun is fired, allowing the case to become unsupported in the head area. Evidence that headspace is seen
in the shape and condition of the barrel locking lugs on the front faces.
If they take on a noticeable stepped appearance, with the upper areas farther rearward than the lower, original location of the faces...there's a good chance that your static headspace has increased to an excessive level, and this stepped deformation can occur on the slide's lugs as well as the barrel's.


When the lugs deform, the static headspace increases by the same amount as the deformation. Rolled lugs...rounded off at the corners...aren't a sign of excessive headspace, but if allowed to continue for very long can lead to it.
that damage is due to other issues besides the straight-line deformation...also known as "Slap-Seating."

Slap-seating occurs because of excessive barrel endplay in the slide. Lug deformation will occur with enough use, but the less endplay that you have, the longer it's delayed. The reason is simple. More end-play means that the slide and barrel lugs have a longer running start at each other before they
engage...but deformation will occur even with zero endplay. It just takes longer to get started. Likewise, the better the lug engagement that is persent, the more the lugs resist deformation. Full depth delays it. Equal horizontal engagement with all three lugs delays it. Very few production barrel and slide combos provide equal lug engagement. Many don't provide even two. If we're lucky, the single lug that engages horizontally is the first one, which is the strongest and most supported. It will deform slower than the others, but the depth of the lug's engagement determines how slow or fast that will occur.

Working, or "Live" headspace is determined as the difference between static and the length of the cartridge case in the chamber. This will vary according to the length of a given case. You can have minimum static headspace...slip a GAP .45 round into the chamber...and produce excessive headspace. This is the type of excessive that isn't dangerous, and works the same as reaming the chamber too deep.

When you look over your pistol, you can check a few things to determine how well your barrel to slide fit is to some degree by using a dial caliper to measure the barrel's endplay in the slide. Slide off, push the barrel back as far as it will go and measure the distance between the muzzle and the bushing. Then force the barrel fully forward and measure again. The difference is the amount of endplay that you have. Not precise, but close enough for government work.

To check the vertical engagement, put the gun together and slip a 1/8th drill rod, (or even a piece of popsicle stick to fit the breechface) between the hood and breechface. Measure carefully from the top of the slide to the top of the barrel. Take the rod out and measure again. The difference is roughly the amount of vertical engagement. Ideally, you want the full depth of the lug...or about .050 inch. Again, most production guns don't provide that much, and usually fall between .042 and .045 inch. Some don't go that deep.

Checking for equal horizontal engagement, or to determine which lug(s) are bearing is a little more involved. You need to use gauge blocks to determine the locations of the rear lug faces within the slide, and measure the distance from the rear of the barrel hood to the front barrel lug faces. If you have clearance between the hood and the breechface, you need to measure that
and add it to the hood to lug face dimension. You'll probably be surprised to find that only one lug is taking the heat...and it's probaby not going to be lug #1. In case you don't know, #1 lug is the first wall ahead of the chamber, and it doesn't have a slot behind it like the others do.

In searching for a good pistol, you may want to have a machinist whittle out a set of headspace gauges from cold-rolled steel...which will be soft, and not very long-lived, but will be adequate for occasional use. .898 Go and .920
NO-GO...and you can probably get by with just the NO-GO gauge, since I've never found a Norinco or any other factory-built 1911 that wouldn't go to battery on the GO gauge. If the gun goes to battery easily on the NO-GO, you probably need to leave the gun laying unless you can get the price down enough to pay for another barrel and the fitting. Note that all the Norincos would come very close to going to battery on a NO-GO gauge. To the untrained eye, it appeared that they actually did. You'll have to look closely at the rear of the slide and frame alignment to see if there's a difference. If the lugs are deformed and damaged, you can about bet that the headspace is excessive, and in the dangerous direction.

I bought 4 of the Norincos that I looked at, and rebarrelled all 4...because I wasn't comfortable with the barrel fit on 3 pistols...and one because it was so bad that 500 rounds would probably have put it over the NO-GO limit.
The three that were okay were slated for hard use, and would have done fine as they were if they had only been intended for limited use and/or carry.

Hope this helps.

 

[1911Tuner]

Addendum

Okay...Had to jump off because the dogs were hollerin' for my attention.

A step further in explaining headspace details is to add, due to dimensional differences between cartridge case length and static headspace, there is almost always an "excessive" live headspace condition. The exceptions are...
with a bolt-action rifle, the cases are fire-formed to fit the chamber, and neck-resized only to prevent setback of the case shoulder. Bottleneck cases headspace between the boltface and the stop point on the chamber shoulder...called a datum line. Known as headspacing on the shoulder. With straignt-walled pistol cases, the headspace is set by the breechface and the shoulder that arrests the forward movement of the case. These cartridges headspace on the breechface and the case mouth...or headspacing on the mouth. This is why roll-crimping a straight-walled pistol case isn't a good thing to do. In order to eliminate "excessive" headspace in a pistol that headspaces on the mouth is to custom fit a barrel with the chamber reamed to below minimum and trim all brass that is to be used to the exact same length as the barrel chamber from breechface to shoulder. Impractical, but doable if one is willing to take the time.

Rimmed revolver cases headspace on the rim and the recoil shield...known as headspacing on the rim. Belted rifle cases headspace on the belt. One noteable exception is the older .38 Super setup in which you had a straight-walled pistol case that headspaced on the rim like a revolver.
These had accuracy issues until recently designed barrels allowed it to headspace on the case mouth.

This "excessive" headspace is known as simply..."Headspace" which is defined as the difference between case length and static headspace dimension.
It may be only a little...or it may be a lot. Revolvers...for example...typically operate with about 5 or 6 thousandths of headspace, and can never work with "Zero Headspace." The rims would drag on the recoil shield and tie up the cylinder. So...a little headspace is a good thing, as long as it's not truly excesive in terms of going outside of allowable tolerances. In the case of the .45ACP, these tolerances are generous. .022 inch from minimum to maximum blueprint specs.

EDIT TO ADD:

Check your E-mail. A forum member sent me a link showing a picture of three barrel lugs that you don't want to see in your gun. I've sent it to you so you'll have a clear idea of what to look for.

 

[1911Tuner]

E-mail Picture

Combatant...E-mail sent with photo showing badly deformed lugs.
Subject line "Ruined Lugs" Scanned by Symantec.

 

[a454me]

Tuner ,
I had a problem with a Norinco barrel earlier this year ( which you helped me with ) I later bought a barrel/slide assembly off EBAY and put on the same gun , After shooting it this weekend I've noticed the barrel lugs looking like they're deforming . I also noticed a mark where the extractor seems to be hitting the barrel . Is the damage usually to the barrel or have you also seen some slides damaged ? Do you still recommend the Springfield Armory barrel for an "easy to fit" replacement ?
thanks

 

[1911Tuner]

Hits

Tuner ,
I had a problem with a Norinco barrel earlier this year ( which you helped me with ) I later bought a barrel/slide assembly off EBAY and put on the same gun , After shooting it this weekend I've noticed the barrel lugs looking like they're deforming . I also noticed a mark where the extractor seems to be hitting the barrel . Is the damage usually to the barrel or have you also seen some slides damaged ? Do you still recommend the Springfield Armory barrel for an "easy to fit" replacement ?
thanks

Barrel lugs deforming how, exactly? Rolled/radiused on the top front corners, or have they taken on a sort of stair-step appearance. Two different things cause both. In Combatant's pistol, it was a whole lot of the former, with a bit of the latter starting soon after.

Extractor contact with the barrel face happens in some pistols, and it's a spec/tolerance stack issue with the barrel, slide, and probably the extractor
too. You can angle cut the nose of the extractor to see if it provides enough clearance...and even a little out of the area on the barrel...but go easy on the barrel. if a little won't do it, a lot won't do it either..at least until it gets to the point of too much.

I'll E-mail the picture to you so you can see if this is the deformation on your lugs.

Stand by...

 

[forquidder]

Vertical engagement

Tuner,

I saw the original post where a pistol was purchased and the barrel lugs were being rounded off. I then clicked on this thread and decided to take a officers model out of it's rug to take a look and a few measurements as per the numbers you posted in this thread.
I noticed the front edges on the first two barrel lugs were slightly angled (not really rounded) near the top. The corresponding lug edges on the slide were slightly worn but not as bad.
So I took a few measurements and the first I came up with was that I'm getting approximately ten thousandths vertical engagement between the barrel and slide. The small angles on the top edges of the lugs are about as deep as the lugs are being engaged. Not good.
Not being an expert 1911 gunsmith, my guess is that I either need to lengthen my existing barrel link or buy a new, longer link and install it.
Any advice?

 

[1911Tuner]

Vertical

Hi forquidder,

Using a long link to increase vertical engagement isn't a good way to go at it.
For one thing, standing the barrel on the link doesn't provide good support,
and usually causes accuracy to suffer. It also puts a strain on the link and its mounting pin that those parts weren't designed to bear...wallowing out the
pin hole in the lug and putting strain on a narrow part of the slidestop pin itself. It also puts the loading farther down on the lower lug feet, and...if the link is long enough to actually cam the barrel into lock as it swings a little past vertical, puts a hard strain on the whole group of related parts when the gun fires.

A longer link also delays the unlock and linkdown timing of the barrel, possibly allowing the barrel to hit the vertical impact surface before the lugs are completely clear of their mating slots within the slide, which will cause some expensive damage to the barrel and slide...even as far as separating the lower lug from the barrel and/or shearing the locking lugs.

Insufficient vertical engagement depth is generally caused by one of two things. Either the lower lug is out of spec,(height) or the slide's installed height is too far from the centerline of the slidestop pin. This can be due to a pinhole mislocation...low...or a stacking of dimensions in the slidestop pin, frame rails, slide rails, and even the slide lugs and slots. All individual parts may be within spec, but together, the tolerances add up to throw the whole
group out.

Sounds like you need a smith who understands how to massage the pistol back into acceptable dimensions. You may simply need a new barrel...and you may need more extensive work. I'd contact Colt and see what they sugest. One that's that far off the mark, they may be willing to correct it even if it's exceeded the warranty limit, or at least, do the work on the cheap.

Sorry to be the bearer of bad tidings...

 

[combatantr2]

Tuner;

Got your email and photo, thanks. Surprisingly, my NORC arrived this afternoon. I'll be break-in shooting this pistol this Saturday for a little test run. Re headspace and barrel lug issues and problems, unfortunately, this is a not too common lingo among local g'smiths here in DVO (RP). I have yet to encounter one that is knowledgeable with these issues. Though it seems this topic is way too technical for me i shall try to digest each and valued detail and discuss this with my preferred g'smith. I shall also try to take and post pics of my new NORC once i get the chance to borrow a digital camera.

One stupid solution (i guess) regarding lug deformation - it seems deformed lugs are crashing against the slide lugs. Is it logical to file down (or sand it down) the file lugs to minimize crashing contact against the slide lugs?

Thanks in advance.

 

[1911Tuner]

File?

The question:

One stupid solution (i guess) regarding lug deformation - it seems deformed lugs are crashing against the slide lugs. Is it logical to file down (or sand it down) the file lugs to minimize crashing contact against the slide lugs?
*********************

You can do that, and it'll make'em look better...but it won't solve anything, and will probably make it worse. The barrel lugs always have the "crash" contact with the mating lugs in the slide whenever the gun fires. Simply put...pressure drives the bullet into the rifling, holding the barrel forward.
The same pressure drives the slide backward, and the lugs engage each other under pressure, and lock the breech. When the barrel lugs deform, the slide moves farther from the barrel under pressure, and working headspace increases by the same amount of distance as the lugs have set back.

If the condition worsens...and it will if you fire the gun a lot...it will eventually reach a dangerous point in which the case backs out of the chamber as it follows the slide...and the case loses chamber support. If that goes far enough, it will cause the case to rupture in the area adjacent to the barrel ramp. (aka barrel Throat) Hot gasses and shards of brass vent downward into the magazine, and...if you're lucky...don't cause sympathetic detonation of other rounds in the magazine. Best to either get it repaired or limit the gun to carry service and shoot it only sparingly. Just enough to periodically check for function.

 

[forquidder]

Thanks

Thanks for the info Tuner.
Although I'm not happy about spending the extra money to get this fixed, it is an OM that actually works.
Watch, I'll get it fixed and it won't work.

 

[combatantr2]

Tuner;

A friend of mine who is a die-hard of FLGRs has this interesting theory on the crashing barrel lugs. He said one probable cause for this could be the recoil spring kinking up towards the barrel thereby obstructing barrel movement downward timing, causing the barrel to crash against the slide. W/c he said is common among 2 piece standard guide rods. Could it be?

I know FLGRs relevance in the 1911 is a touchy issue and infact i never use one.

Thanks.

 

[Old Fuff]

combatantr2:

If your friend ever took the time to look at the original Browning design he'd see that his theory was all wet. At the back the recoil spring is threaded onto a guide. Obviously it can't kink at that end. On the front it is enclosed inside of a cap (called a "plug'). As the slide travels backward compressing the recoil spring the plug slides over the guide on which the spring is being compressed. Since the recoil spring is in one way or another, contained at both ends it is unlikely it's going to kink or bend.

If you want to confirm this, take a regular, full-sized 1911 pistol with the standard recoil system, and after removing the magazine and then inspecting the chamber to be sure it's unloaded, take an ordinary wood pencil and push on the recoil spring plug. As you push the plug backwards you can feel if the spring is kinking or not.

The Browning/Colt system was used since 1911 without any modifications, and never was thought to be a problem until the current crop of gamers came along, starting in the 1970's. Ever since that time we have been seeing reliability problems in "old slabsides" that were never noticed before.

I wonder why...

 

[1911Tuner]

Kinky Spring

Fuff hit it. The standard spring guide OD is pretty close to the spring ID.
The plug ID is pretty close to the spring OD. The spring compresses equally from both ends and in the middle. As the spring compresses and shortens, the coils climb over the guide rod while the plug climbs over the spring. At full travel, which is only about 2.25 inches, the spring is almost completely encapsulated by the guide and the plug...inside and out...with very little room for deflection in either direction.

Your friend needs schoolin'.

 

[combatantr2]

I have faith in you guys

 

[Old Fuff]

I have faith in you guys

Tuner and I are right of course...

But you can test our answers if you have access to an ordinary, full-sized 1911 style pistol with the Colt/Browning recoil spring system. All you need in addition to the pistol is an unsharpened wood pencil to push on the Recoil Spring Plug with. You can't of course, do this if the gun is equipped with an aftermarket FLGR.

In my opinion, the only advantage the FLGR offers is a little more weight forward, that helps balance the pistol and slightly lessens felt recoil. But they are more bother then they're worth. This is yet another gadget dreamed up by some gamers, hoping to get a slight edge. If they believe it works that's fine, but I don't.