SMG IMI Uzi Jamming

[fishtix]

Hey all, new to me IMI - Model B NFA SMG owner here. First uzi.

Looking for some much appreciated guidance from the sages on this side. Basically getting nose up unfired rounds on 9mm that has COAL greater than 1.150" (which kind of stinks becuase I have tons of subsonic reloaded at 1.150" that fire in my macs just fine).

-IMI Model B, full SMG coversion by the late Richard Hoffman w/ his feed ramp
-Top cover gap is about 0.005"-0.007"
-Mags mix of IMI, German & Meccgar

I've scoured the search function, Dave's book and found some ideas (too tight top cover, mag height, ejector issues etc). I figure it may be an easy fix someone has dealt with before, and before I start messing and changing things, I thought I would ask. I've have / had other SMG's and am no stranger to tweaking things to get things going, but this is my first full size uzi.

Brought it out the first time yesterday. Blazer brass, 200rds 115gr 9mm shot 100%.

Winchester, both 124gr nato head stamp and 115gr WWB jammed with somewhat of a stovepipe every 2 sometimes 3 rounds which was unfortunate because I had double the WWB & 124gr nato with me.

I measured the Blazer brass 9mm COAL, very very consistent on average 1.126".
WWB 115gr & Win 124gr nato, COAL was all over the place. anyhwere from 1.120" to 1.174"

What I found is that as, it runs fine on Blazer brass 9mm ammo, which all from sampling assume to be less than 1.150". Anything longer and I get a weird nose up type jam with the cartridge rim deforemed by the lip under the bolt face as evidenced by the WWB & WWB 124gr.

-Played mix and match with ammo and about 20 mags, result was the same with longer rounds so I am assuming the mags are OK.

Thanks guys for the help!

 

[AKarms]

Gap could be too large for subs. I find subs need a tighter top cover gap. Also if you’re running pro mags that itself will cause an issue. And being that they’re reloads that’s another variable. It’s probably going to be trial and error to get them to run properly

 

[AKarms]

And another thing, sometimes you have to open chamber mouth and polish to feed subs properly. I just do this on every barrel now

 

[AKarms]

If you can’t get it worked out, gimme a shout 6033404339 I’d be happy to go through it for you. But if you can tinker, you should be able to work it out

 

[bigu2fan]

How is your extractor? Possibly worn out? Blazer Brass, in my experience, tends to be on the weak side of 9mm ammo. It does not run my RR IMI reliably. I also get jams (failure to eject). Switch to S&B (which is a hotter round) and it runs pretty much 100 percent. I swapped extractors awhile ago. How about your recoil spring? Is it possibly worn out?

 

[fishtix]

Haven't run any subs through it yet. I was just saying I have a boatload of sub reloads that I load at COAL 1.150". Just ran blazer brass 9mm 115, WWB 115 & WWB 124 so far. The common denominator seems to be COAL over 1.150" causes issues.

Blazer brass ran 100%. Extractor looked clean and fine.

I apologize, I should have said nose up unfired round.

 

[bigu2fan]

Haven't run any subs through it yet. I was just saying I have a boatload of sub reloads that I load at COAL 1.150". Just ran blazer brass 9mm 115, WWB 115 & WWB 124. The common denominator seems to be COAL over 1.150"

Blazer brass ran 100%. Extractor looked clean and fine. But the issue isn't FTE.

My mistake, the jamming I was referring to were fired cartridges that did not eject and were stuck in a stovepipe fashion. They would be extracted from the chamber, bumped out of the claw of the extractor (but not out of the gun) and then the bolt would slam the empty back into the chamber in a funky angle with a live round in the chamber.

 

[AKarms]

How is your extractor? Possibly worn out? Blazer Brass, in my experience, tends to be on the weak side of 9mm ammo. It does not run my RR IMI reliably. I also get jams (failure to eject). Switch to S&B (which is a hotter round) and it runs pretty much 100 percent. I swapped extractors awhile ago. How about your recoil spring? Is it possibly worn out?

I run blazer brass in every smg that comes through my shop as a baseline. I’ve yet to have one that won’t run it in 3 years. That’s crazy yours won’t. It’s the most reliable 9 I’ve ever found for uzis

 

[AKarms]

My mistake, the jamming I was referring to were fired cartridges that did not eject and were stuck in a stovepipe fashion. They would be extracted from the chamber, bumped out of the claw of the extractor (but not out of the gun) and then the bolt would slam the empty back into the chamber in a funky angle with a live round in the chamber.

Replied to your other comment before seeing this

 

[AKarms]

Haven't run any subs through it yet. I was just saying I have a boatload of sub reloads that I load at COAL 1.150". Just ran blazer brass 9mm 115, WWB 115 & WWB 124 so far. The common denominator seems to be COAL over 1.150" causes issues.

Blazer brass ran 100%. Extractor looked clean and fine.

I apologize, I should have said nose up unfired round.

Nose up is usually feed ramp/barrel issue, or something is slowing bolt down. Have you tried another barrel?

 

[bigu2fan]

I run blazer brass in every smg that comes through my shop as a baseline. I’ve yet to have one that won’t run it in 3 years. That’s crazy yours won’t. It’s the most reliable 9 I’ve ever found for uzis

Wow, ok, thank you. I will say my RR IMI still has the barrel restrictor ring installed. The surplus IMI SMG bolt I am running has been "clearanced" for use with the restrictor ring, however, it still ever so slightly "bumps up" when it interfaces with the barrel restrictor ring just before it gets completely into battery. Do you think this might cause the gun to jam on Blazer Brass but not on the more hotter loaded S&B?

 

[AKarms]

Wow, ok, thank you. I will say my RR IMI still has the barrel restrictor ring installed. The surplus IMI SMG bolt I am running has been "clearanced" for use with the restrictor ring, however, it still ever so slightly "bumps up" when it interfaces with the barrel restrictor ring just before it gets completely into battery. Do you think this might cause the gun to jam on Blazer Brass but not on the more hotter loaded S&B?

Yea I’d say that’s another issue and the hotter ammo is able to cycle through the issue

If you ever want to update it to smg spec let me know

 

[bigu2fan]

Yea I’d say that’s another issue and the hotter ammo is able to cycle through the issue

If you ever want to update it to smg spec let me know

Check out these attached photos with the circled area. The bolt appears to have been parkerized after being "clearanced." Notice the areas where the parkerized finish is worn. That appears to be where it is ever so slightly making contact with the restrictor ring. What do you think? Is that enough to impact functioning?

 

[Slowmo]

Make sure you are really pressing the grip safety all the way in. If not, it can drag on the bolt.

 

[AKarms]

Check out these attached photos with the circled area. The bolt appears to have been parkerized after being "clearanced." Notice the areas where the parkerized finish is worn. That appears to be where it is ever so slightly making contact with the restrictor ring. What do you think? Is that enough to impact functioning?

That will absolutely cause issues

 

[bigu2fan]

That will absolutely cause issues

I just sent you a private message

 

[Nome Nomad]

I had issues with my uzi when I first got it, stovepipe and ftf. I found it was my barrel chamber being too tight (aftermarket barrel) switched to a factory IMI barrel, no issue then extracting. However, I would still get ftf. Found my bolt's firing pin was worn. Tossed in a new bolt and it's been humming along with zero issues for years on every ammo except flat point.

 

[gorillastomp]

Magazine height is something else to look at. If it’s to high it will drag to low it will strip but doesn’t feed into the barrel well.

Pictures are worth taking also of the jam. Years ago I had an issue similar to this. My extractor looked fine but once I removed it from the bolt. I discovered it was completely gummed up with carbon buildup cleaning solved it.

 

[KickStand]

I’m new to Uzi’s but recently got two on a trade. One was nib box and the other was used. It was made clear to me that the used one wasn’t working 100%. I figured it would be an easy fix. When I first tried it, the ejection seemed weak and was getting stovepipes. I first looked at the extractor and saw 45 engraved on it and I told myself that’s the problem and replaced it. Unfortunately, that didn’t fix it and I went down a rabbit hole and even reached out to a few people on here for assistance. I also watched all of the videos from bwe. I tried everything and couldn’t get it to eject right. Everything looked fine, tested fined and I tried this and that.
Well, I said the barrel is the last thing that I haven’t changed. I changed the barrel with a cheap KAK barrel and it works 100% with factory ammo now. Unfortunately, the KAK barrel doesn’t like my reloads. The barrel needs more of a funnel at the leading edge of the chamber.

 

[fishtix]

Thanks guys, I'll try a new barrel first then mag height adjustment. I'll snap a few pics too.