chamber not lining up with bolt face?

[UZIGUY1]

Hi all,
got a barrel for the smg from GB and it would appear that the chamber is off slightly? i.e. the cases are getting clipped on the right hand side slightly by the bolt face and getting light strikes and FTF?

anyone ever seen this before?

 

[brenbuilds]

Did this behavior begin after installing this new barrel? If so I would evaluate the barrel. Is your UZI a registered receiver or a registered bolt in a host gun?

This could occur if your trunnion is out of alignment, but if it began with a new barrel I would purse that first. Can you provide more details on your gun? Has it been converted to SMG specifications?

 

[barrelxchange]

Need a picture of chamber end of the barrel

 

[UZIGUY1]

hi all,
its a IMI registered receiver gun, will get a pic of the chamber end, i have notice that there is not as much chamfer on the barrel as on the original IMI barrel, could that be the issue?

thanks

 

[UZIGUY1]

here is the comparison pic

 

[K2]

Hi Uziguy1,

I'm a bit short on details. Do you have a barrel that works in the gun that came with the gun?

You indicated a SMG barrel? That will no fit in an IMI S/A trunnion. With that said, is the barrel cut to fit a S/A trunnion or was the trunnion replaced or re-bored?

If the trunnion was just re-bored or replaced I'd guess that the machinist/smith didn't get the alignment right. This may take some work to repair.

BTW, if checking alignment, use a de-primed empty cartridge case and remove the extractor from the bolt.

Enjoy the ride,

K2

 

[UZIGUY1]

Hi K2,
its a registered receiver with smg bolt and barrel, was done in 82, it runs perfect with the original smg barrel that came with it but i bought another barrel from GB to save the original.

do the chamfer differences make big difference?

thanks

 

[barrelxchange]

Need a pic of the end of the chamber (looking into it).
Could just be bad throating on the barrel.

All original SMG barrels I have seen have a nice chamfer at the chamber.

 

[emrisg]

I had a green mountain barrel that was not tapered enough and would not run.

 

[UZIGUY1]

so i just remembered i had an endoscope!!m took a while to find it though. here are some pics of the misalignment, i am tempted to give Richard at BWE; method of adjusting barrel alignment a go?

thoughts?

 

[StenAtopia]

so i just remembered i had an endoscope!!m took a while to find it though. here are some pics of the misalignment, i am tempted to give Richard at BWE; method of adjusting barrel alignment a go?

thoughts?

Is there an Uzi barrel alignment trick hack somewhere? I know of the Mac’s but never seen a Uzi one? Since Richards passing the only ones I’m confident with is Sam at PS and Andrewski! Ymmv.

 

[UZIGUY1]

Is there an Uzi barrel alignment trick hack somewhere? I know of the Mac’s but never seen a Uzi one? Since Richards passing the only ones I’m confident with is Sam at PS and Andrewski! Ymmv.

if you look at Richards trunnion reweld you will see how he makes the final adjustments, thats what i was thinking of doing.

 

[StenAtopia]

if you look at Richards trunnion reweld you will see how he makes the final adjustments, thats what i was thinking of doing.

Banging on the table method. I love it and it works. Put an aluminum rod through your barrel, it should align though the rear plate opening. If it doesn’t then you will know “which way to bang the barrel”?

 

[brenbuilds]

Try scoping it with your good barrel. It's possible the new barrel is "out of round", and the lack of concentricity renders the barrel offset in the trunnion.

 

[ScottinTexas]

Hi all,
got a barrel for the smg from GB and it would appear that the chamber is off slightly? i.e. the cases are getting clipped on the right hand side slightly by the bolt face and getting light strikes and FTF?

anyone ever seen this before?

I had this exact problem with a Group Vector FA.

It ran fine with the original barrel.

Bought a Green Mountain and I got light strikes frequently with all brands.

Turns out the outer profile of the GM barrel had a sharp break vs. the smoother more rounded profile of the factory barrel. So the upper face of the bolt was glancing off the upper outer edge of the barrel generating light strikes.

I ended up smoothing the GM barrel with a file and sandpaper; problem solved. But it's probably a misaligned trunnion ultimately.

 

[K2]

Hi OP,

A very generous chamber will likely be less sensitive to the alignment.

In your RR, what is left of the restrictor ring? I'm going to guess at least the top is cut off the ring. The photos you supplied indicate that the barrel is lower than the C/L of the bolt. Swing away.

16" barrels work good. As Richard would say "don't beat the hell out of it" .

As an afterthought, what do the scope photos look like with the old barrel? If that is not aligned with the old barrel it may be an issue of the re-bore of the trunnion to be in error. The generous chamber of the old barrel may have just masked alignment issue.

Enjoy,

K2

 

[K2]

Hi Uziguy1,

Curious about the resolution. I should have thought of rotating the barrel 180 degrees and doing the scope again. (Yes, loosen the barrel nut.) Anyway, if the offset follows the rotation of the barrel, the barrel has problems. If the offset stays in the same place relative to the gun, there are some trunion alignment concerns to be addressed.

From Dirty Harry "I gots to know."

Enjoy,

K2

 

[Jones]

Here are ths specs on chambers. Might help to narrow down the area(s) you need to pay attention to.
This is for a mini but all the 9mm chambers are the same.