Green mountain barrel getting clipped by the bolt?

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Hey guys, I recently got ahold of some new 9mm SMG spec GM barrels for my semi auto McKay build Uzi (with an Israeli kit trunnion and SMG feed ramp). I've noticed that the top left edge of the chamber side of the barrel has been getting contacted by the semi auto bolt I'm running. I read in a few places that the GM barrels have been known to have these issues sometimes, along with the inner diameter of the chamber being rough and causing feeding issues. Anyone have a similar issue, and was able to resolve it at home? I don't have access to a machine shop with a lathe unfortunately.
 

ScottinTexas

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I had this problem with a GM barrel in my GI Vector FA Uzi.

Had lots of light strikes.

Turns out by comparing the chamfer of the outer edge of the GM barrel vs. the factory GI Vector barrel revealed the GI / Vector had a smoother radius. The bolt was hitting the top of the GM barrel and just riding over the same spot on the GI / Vector barrel.

I carefully hand-filed the outer edge of the GM barrel, then sanded and finally dremelled with a flitz-drenched pad. That solved the problem. Yes, it would be easier with a lathe but I don't have one.

Ultimately I think this is not really a GM problem but a misaligned / slightly out of spec trunion to receiver weld. Likely the barrel muzzle is tilted slight downward vs. horizontal.
 
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Shit. It's good to know what the issue is, but it sucks knowing that the trunnion might be tilted. On YouTube I watched Richard from BWE Firearms simply use a dummy barrel locked into his trunnion as a way to whack the trunnion against a table and slightly adjust it, but I don't have a dummy barrel. The barrel looks like it's concentric with the rest of the gun while peeping through the rear stock hole, but I know that isn't the most reliable way of telling. Guess I'll grab a hand file and some sandpaper and start with smoothing out the top of the GM barrel, then work from there.
 

emrisg

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I have a green mtn barrel that is not reliable in my fa Uzi. My gun was brought to full imi full auto spec by BWE. Green mountain refused to help me. There barrels are not to spec.
 
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I have a green mtn barrel that is not reliable in my fa Uzi. My gun was brought to full imi full auto spec by BWE. Green mountain refused to help me. There barrels are not to spec.
I’ve seen multiple people online state the same thing. They own Uzis that were professionally built, they get a GM barrel, and suddenly theres issues. Just sucks that there isn’t much surplus IMI barrels available anymore. Did you resolve your issue with your barrel or do you just not use it? I took a dremmel, some sandpaper, and finally some steel wool to mine and it seems to have resolved it, although only time will tell. Can’t really tell if the barrel is still being contacted now because it’s sanded down to bare metal lol
 

emrisg

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It’s just sitting in my parts box. You can see the difference when comparing it to a imi barrel. I was lucky to buy several new imi barrels when I got my gun. I bought the green mountain as a beater but it is too unreliable.
 

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