New FA Uzi with Feed Issues. Ugh, please help!

[Southern Raider]

After a lengthy wait with the ATF, the paperwork for my Uzi arrived and I took it for a test drive today. I didn't shoot it as much as I hoped, since it has a peculiar feed issue I'm hoping somebody recognizes.

The gun is a registered receiver IMI Model B that still retains most semi-auto features with the exception of the blocking bar. The gun will run for a bit in FA then jam. The jam is a bullet tip lodged against the top of the chamber and only happens when the round is fed from the left side of the magazine. Several mags were checked (German 32-round mags bought from RTGParts).

One thing I noticed is that when a mag is inserted, the left side rounds are pinched against the underside of the ejector. I'm fairly certain that this is causing a slightly steeper feed angle for left side rounds and is probably the cause of the misfeed, but this would be present in all guns.

As a side note, I did notice the the tack welds for the barrel restrictor ring are broken and it does wiggle a bit with the barrel removed, but tightens up with a barrel locked down. The barrel still seems more constrained with it in than it would otherwise be. I want to get this fixed, but I don't think this is the root cause here.

Any ideas?

 

[mrbmist]

What type of ammo?

Rationale is: some flat tip and/or JHP ammo tend to do as you described. Have you tried round tip ball ammo?

I ran into a similar issue on one of mine, I removed the bolt and top cover inserted a mag with ammo and fed a few rounds by finger, my feed ramp was the culprit. The rounds would hang up on the barrel lip. It just didn't like flat tipped ammo, whereas round tip ammo runs fine all day long.

My IMI Mod A eats everything I feed it... Just my 1 Cent (1 cent due to recession)

 

[Southern Raider]

Ammo today was a mix of WWB, Remington UMC and a few old IMI rounds. All was 115gr round nose ball ammo.

 

[9mmsubgun-m11]

Try some 25rd mags-they are ultra reliable. The 32rd mags are notorious for issues feeding from left side-The IDF were not issued 32's because of this. You may also want to avoid Remington 9mm as it is too weak to reliably cycle most open bolt guns. HTH.

 

[xichlo]

What type of ammo?



My IMI Mod A eats everything I feed it... Just my 1 Cent (1 cent due to recession)

More like 12 cents due to all the money printing and inflation

 

[abundigas]

I had a similar problem with a new barrel I had purchased from Vector, I compared it to the factory barrel and noticed a sharper edge on the lip of the chamber, I took some valve grinding paste and a rag, and spend a few minutes spinning the Barrel on the tip of my finger, just enough to smooth out that lip, and have not had a FTF since.
If no Valve grinding paste, some 1000, of 1500 wet sand paper can work also.

 

[Southern Raider]

Thanks for the tips. I took a closer look at stuff and think I see what may be happening.

I loaded a mag with some snap caps and very slowly cycled the bolt back and forth. The first thing that stuck out is that the bolt was hitting the mag then overruning it. I did a few measurements and it looks as if the German mags have a bit less space (0.005" - 0.010") at the rear for the bolt to pass through. A couple swipes of a file resolved that. I also polished the sharp edges of the feed lips with sandpaper for good measure.

I was able to recreate the left side feed issue this way. A smack on the rear of the receiver cause the snap cap to fuly chamber, so I'm guessing the above problem may have been robbing the bolt of the energy to reliably chamber a round. I'm not sure where it has a preference to fail on the left side, but I'll follow up with an inspection of the bolt for burrs in that area.

I do have some IMI mags, including a 25 rounder, to try next time. Hopefully that's all it is.