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Barrel Lug Flanging


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I need some help understanding the causes of barrel lug flanging. I was running some factory 9x23 ammo through 3 limited class 1911 barrels (no compensator) and noted flanging on the barrels' upper lugs after 50 rounds or less. These were 'drop-in' barrels, not full house rebuilds. Barrel fit was ‘fair’. One barrel had some front to back slop, the other two did not. The amount of lug engagement was not measured prior to firing; it was ‘fair’ for one, good for another, and unknown for the third. There was no concomitant damage to the slide's lugs. I did a brief timing test (not very thorough) and noted no obvious issues, but the timing might have been imperfect.

The first question is what causes the flanging? If I were to guess I’d say that a couple factors might be involved. One is insufficient lug engagement. Another guess is there sheer power of the cartridge = slide velocity. A third is timing.

Okay folks, educate me! What causes it and how do I stop it?

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My opinion is this: If the barrel is timed right and fitted right this won't happen. You might beat the snot out of the gun, but it won't flange the lugs.

Flanging is from the barrel being slammed forward into lockup with the upper lugs. Depending on the load this might only take a couple thousandths of hood length clearance to let the barrel hit the lugs HARD. If upper lug engagement depth is short it will be greatly accelerated too. If it is timed a little early it will pull the lugs from lock with a good deal of pressure still locking them to the slide, this will roll the edges and tear the heck out of both the lugs and the slide. You can cheat timing a little with firing pin stop geometry and mainspring weight, and to a very slight degree with hammer strut length. It won't make up for a poorly fit barrel though.

Send those barrels to EGW, have the hoods and lugs welded up, then fit them right if you want to continue.

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How much contact area does the barrel have? You can coat the locking lugs with a black magic marker then shoot a few rounds and see where the lugs are contacting.

Do you have full lug engagement? If not, the barrel will need fitted correctly.

Do you have all three lugs contacting? If not, measure the spacing of the slide lugs and the spacing of the barrel lugs and see which one is off and how much. If they are off a few thousands, the flanging may stop when they wear in and all 3 contact. If they are off considerably more, send the part back and get one that is correct.

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thanks for the input.

the recoil springs were 18 and 20 lbs. Hammer spring for one gun was 19 lb, unknown for the other, probably an old Colt factory spring.

in one case i noticed a gap between the rear barrel lug and the slide lug, and wondered if that contributed to the problem. sounds like it might. in the other cases lug fit in that region was pretty good.

obe barrel is a Nowlin 9x23 barrel and it seemed like it did not have much lug engagement when inspected. NOTE, i don't blame the barrel- i don't want hate mail from Nowlin!

one gun is an old series 70 Colt. its original barrel had severe flanging. it had hardly any lug engagement. the collet bushing was binding and prevented the barrel from pushing up very much during lockup. in this case it pointed very clearly to the amount of lug engagement as a possible cause of flanging, and that was one thing i looked at with the other barrels, though i did not measured it.

keep it coming!

Edited by superdude
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