UZI "B" failure to feed after first round

[dherman304]

I have an Action Arms Uzi marked as 45 but came with 9mm barrel and bolt. (functions flawlessly in 9mm) I bought a stripped IMI 45acp bolt and 8.5" pike arms barrel and some SGM metal 45acp magazines. I reassumbled the gun in 45 and it loads and shoots the first round great but it gets stuck on the next round (See pictures)

Whats interesting is the very first 3-4 rounds ran fine, then it started happening. Any idea whats going on here, I know there are a lot of variables here but dont even know where to start. Was thinking about polishing the chamber?

 

[slimshady]

Have you tried changing ammunition brand?

 

[ToddA]

https://www.uzitalk.com/forums/index.php?threads/finally-got-the-uzi-smg-working-correctly.100546/

 

[Slowmo]

Are you sure the mags are meant for an Uzi? I wasn’t aware SGM made Uzi mags.

 

[AKarms]

I’ve had 2 pike barrels brand new come in with chamber out of spec due to their coating thickness. 9mm.

45 is a problem child anyways, but I’d check chamber specs

 

[Jim in Texas]

A few things to think about:

Does the stuck cartridge always come from the same side of the magazine? For example, does the jam always occur when the cartridge is coming from the right side of the magazine?

How far back does the bolt travel from the first shot? Could it be short stroking compared to how far back the bolt travels when you manually cock the gun?

 

[124NATO]

What does your extractor look like ? I'm assuming it's semi? Do you have a 45 extractor in it and does it have the semi cut on the corner?
One problem can be that round isn't sliding up the bolt face and under the extractor and since it's not fully supported the round can tip up. If you used your 9mm extractor that isn't going to work
Just a thought

 

[Slowmo]

A few things to think about:

Does the stuck cartridge always come from the same side of the magazine? For example, does the jam always occur when the cartridge is coming from the right side of the magazine?

How far back does the bolt travel from the first shot? Could it be short stroking compared to how far back the bolt travels when you manually cock the gun?

Aren’t .45 Uzi mags single feed?

 

[124NATO]

Aren’t .45 Uzi mags single feed?

Yeah there single feed.

 

[dubagel]

I’ve had 2 pike barrels brand new come in with chamber out of spec due to their coating thickness. 9mm.

45 is a problem child anyways, but I’d check chamber specs

When you say out of spec, did a 9mm round not go into the chamber fully? Reason I ask is I just got a pike full size Uzi barrel for my Model A that I SBR’d. I put a few rounds of new IMI ammo in the barrel on the bench and measured and did the same with those same rounds in my factory IMI barrel and the dimensions were the same between the 2 barrels as to how much the cartridge sat in the chamber.

 

[AKarms]

When you say out of spec, did a 9mm round not go into the chamber fully? Reason I ask is I just got a pike full size Uzi barrel for my Model A that I SBR’d. I put a few rounds of new IMI ammo in the barrel on the bench and measured and did the same with those same rounds in my factory IMI barrel and the dimensions were the same between the 2 barrels as to how much the cartridge sat in the chamber.

It was a few thousandths tighter than a factory barrel. Rounds were not feeding or extracting properly. I let pike know about it. Their coating was too thick

 

[Jim in Texas]

So much for my assumption that the 45 would follow the same pattern as the 9mm. I suggest fact-checking a couple other assumptions.

Using a micrometer or caliper, are the external dimensions of the 45 bolt (such as height and width) the same as the 9mm bolt? Just a few thousandths of an inch can cause rubbing that does not occur with the smaller bolt.

Can you compare the chamber bevel or feed ramp on the aftermarket barrel to a factory barrel? Same angle, depth, and transition to the actual chamber? Sometimes, breaking an edge can make a significant difference in how well a barrel feeds.

 

[SecondAmend]

So much for my assumption that the 45 would follow the same pattern as the 9mm. I suggest fact-checking a couple other assumption.

The good news - Having a full-size Uzi with 9mm, .45 ACP, and .22LR conversions is like owning three machine guns.
The bad news - Having a full-size Uzi with 9mm, .45 ACP, and .22LR conversions is like owning three machine guns.

 

[Dirk Hawthorne]

people came up with some good suggestions so far

did you check the top cover clearance with the 45 bolt? may be too tight, dragging on the bolt

off brand magazines cause a lot of jamming problems

what ammo are you using? maybe the gun is short-stroking on weak ammo?