Uzi & pressure ?

[safenate]

Was at the indoor today and picking up some extra 9x19 to my stash, when i saw serious overpressure signs. Primers completely flatened and flowing back into ejector hole. I looked at the stamping (from pressure) on the headstamp and compared it to the bolt face of the rental uzi; sure enough. I've seen many of these range reloads shot in several models with no problems. Would the Uzi chamber get smaller/tighter (due to residue) and need cleaning? Anyone with input, interested. I don't want my local indoor range closed due to a shooter injury. I've emailed the reloader, but he doesn't reply. Thanks.

[GentlemanJim]

I had an A model UZI and it was rough on brass...but no real pressure signs.

Carbine length barrels can do some strange stuff with some powders.

I would check it out with some other brand of ammo...and see if there is a difference.

jim

[safenate]

Here is a pic. I pop'd out a primer with little effort from my fingernail. Not my UZI, but i don't want the K'bm next to me or closing the range.

[Bill Nesbitt]

Does Uzi fire from an open bolt? Does that have anything to do with it?

[safenate]

Yes, it does. Don't know if it matters. Was hoping others may enlighten us.

[SA Friday]

We use Uzi's in OSI. I have shot them for years, mostly with +P rounds. They are a slam-fire SMG (bolt open fire). They strip the round off the mag, chamber the round, and fire all in one pull of the trigger. The firing pin is fixed in place and isn't what one would consider a pin. It's simply a bump where a firing pin would be machined out of the same piece as the bolt. The bump is larger than you would see from a regular firing pin to add extra strength. The only thing that keeps the bolt against the chamber is the strength of the recoil spring. There is no mechanical means per se other than that spring keeping the bolt against the chamber other than the weight of the bolt and the strength of the spring.

These are Federal primers in these reloads, and the slam-fire is smashing the primers to hell. I would suspect they look like that because they are so soft and are getting smashed into by the overly large firing pin. So, what you are seeing is the pin is setting off the overly sensitive Federal primer a tiny little fraction before the bolt has the round fully supported into the chamber. The primer has no support like you would see from a bolt-closed siring sequence and is coming out a bit and buldging, then the cartrtidge is getting fully supported at the end of the bolts forward movement. It appears there is no pressure signs on the headstamp area of cartridge case. The +P rounds we have shot through the Uzi will leave striations on the brass part from pressure. I suspect the pressures are OK, but I would recommend he try a different primer for reloads in the Uzi. CCI's would probably be a better choice or you are going to start seeing some breachface wear from gasses escaping around the demolished primers (not that the wear would really matter, it would be just cosmetic, the Uzi is the AK of the SMG line of weapons IMO).

Edited August 1, 2008 by SA Friday

[safenate]

SA,

Thanks. i noticed what looked like soft, fed primers. i hadn't thought about premature detonation before being completely chambered, great point. The uzi is the AK of SMG. Feed it anything, anywhere & it'll shoot it, all the time.

[-JQ-]

the Uzi is the AK of the SMG line of weapons IMO).

And I love them for that...that would be the next on my Class III list. A buddy has a nice registered receiver (or is it the bolt ) uzi that he can run in 45, 9mm or .22 - that's the one I want.

Fun to shoot and accurate.

SA - sorry I don't have any spare uzi parts for you ;-)

[SA Friday]

SA - sorry I don't have any spare uzi parts for you ;-)

No problem. They are Israeli made, and cannot be brought into any of the Arab countries. We don't have any here and roll with M-4's, 249's, 240's, 203's, and M-2's. Hell, our handguns are just for show at this point. An Uzi would just get in the way.