Colt Trouble

J

John Travis

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Lexington, NC or thereabouts.
Colt 0991 Series 80 Enhanced Government Model, circa 2001. I was living in Rural Hall at the time.

Neighbor bought it lightly used from a local dealer. Pistol was dead reliable, and never missed a beat. About 1500 rounds into it, he noticed something odd with the brass. A weird "U" shaped bulge that was wider at the legs than at the curve...like a V with a radius in the bottom. The legs were toward the front of the case.

Puzzled, he brought the gun to me with a few rounds of the brass. I knew what it was immediately, and a field strip confirmed it. The lower barrel lug was being torn off the barrel, and had pulled all the way through to the chamber, causing the brass to bulge into the defect. The crack wasn't very noticeable and I had to look closely for it. Static on the bench, the chamber would simply spring back into position and the crack would close up.

I estimated that another 50 rounds would have caused it to fail completely.

Clue: It was a spec issue that was easily corrected, but it did require a new barrel. He decided to replace it with a Kart that I had on hand rather than go through Colt's warranty.


What tore the lug off the barrel?
 
Squeezing the trigger too hard? Sorry Johnny, I couldn't resist. :)
 
Obviously failure to install a shock buffer ;-)
 
I’m going with barrel hood too long, barrel forced forward during chambering, strain on the link pushes the rear portion of the lower lug up into the chamber.
 
Lower lug not hitting the vertical impact surface properly if at all.
 
John Travis said:
It was a spec issue that was easily corrected...


What tore the lug off the barrel?
Click to expand...
It's the lower lug.

Aha! The other clue is the V shaped defect, which had the wide part forward. That indicates that the lug was being torn off upon return to battery... not on unlocking, but on locking up.

Lemme work on why a wee bit more...

Was the rear face of the lower lug too short, as in too far forward?
 
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No, the upper lugs would prevent that from happening.

It had to be from slamming into the frame, at the bottom of the tilt.
 
Improperly machined vertical impact surface on the frame.
 
No bad. Not bad. Most of the contributors here have hit all around it.

The vertical impact surface and the lower barrel lug were right where they should be.

The cause of the torn lug is related to all this, and the end result is the same in any case. It's one of only two things that will break a lower lug like that when the link is the correct length.

The barrel was hitting the bed before it was being stopped by the VIS while the link was still trying to pull it down. It can also happen when the barrel hits the bed at the same time as it hits the VIS, though it takes longer for the lower lug to show the ill effects.

The telltale indications were visible as soon as I got the slide off. Bright burnished marks in the frame bed and on the bottom of the barrel from the link pulling the barrel tight against the bed while the barrel was still moving backward.

Either condition will show when doing the field test for stopping on the link, but a separate test is needed to determine which condition is in play.

The field test is to assemble the gun with the slidestop arm hanging vertically...then pushing the muzzle firmly against the edge of a bench as far as it will go...and flipping the slidestop arm to see if it swings freely. If it gets into even a light bind, you have one of the two problems.

The bench test to determine which problem is to cover the barrel bed and the rear face of the lower lug with layout fluid and hit the muzzle sharply a few times with a heavy rubber mallet. Then, disassemble the gun and look at the blued areas. If the bluing has been removed from the bed, there's your bug. If it HASN'T been removed from the rear of the lower lug, the barrel is stopping on the link. If it's being removed from both, the barrel is hitting the bed at the same time as the VIS.

The frame bed is usually the easier of the two to correct. I was able to take care of the Colt in question by removing about .005 inch from the frame bed with a half-round striking file, taking a few strokes and retesting until the bluing remained...and then running the test with the new barrel, and taking a couple more strokes to allow for carbon buildup in the bed.

Correcting for stopping on the link can be a little more involved. It's usually because either the VIS is too far rearward, or the barrel lug is set too far forward on the barrel. and sometimes it's just a matter of tolerances on both parts stacking in the wrong direction. It's rarely because of a short link unless somebody installed one in an attempt to correct a linkdown timing problem.

I never determined whether the barrel or the frame was out of spec, but because it required so little material removal from the bed, I suspect that it was also tolerance stacking.

Just another one of those little oddball things that have made their way to me.

Just a note to let everybody know.

Every stock Norinco I've ever handled has failed the field test. The bind is very light, and most Norinco barrels are tossed due to lug deformation taking the headspace beyond the allowable maximum before the lugs fracture...but every one I've seen fails it. Here, the cause has always been the barrel lug being a little too far forward. So, if any of you has a Norinco with the original barrel, keep watch on the lower lug for signs of an impending crack. Oddly enough, you'll probably be able to see the start of a defect in the chamber floor before it will show on the outside of the barrel.

Cheers all!
 
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Another most interesting case. I once had a Norinco 1911... brought it to you for inspection. It must have had an in-spec barrel, 'cause we didn't do anything to it. Shoulda kept it.

Reminds me of my Para that had a guide rod way out of spec, and was slamming into the link... you got grief on the Forum for fixing a Para with a Colt part. :cool:

Specs!
 
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MacEntyre said:
I once had a Norinco 1911... brought it to you for inspection. It must have had an in-spec barrel, 'cause we didn't do anything to it. Shoulda kept it.
Click to expand...

The way our conversations usually go, I probably got distracted and it slipped my mind. I do remember giving the vertical bazrrel engagement a quick look...I do that to all of;em...and I didn't see anything that warranted measuring it.
 
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