Uzi Mini Bursting in Semi Mode

[uzifan78]

Just picked up a Mini Uzi and have a bit of a problem. It works perfectly in Full Auto, but doesn't cycle properly in Semi.

The bolt doesn't go back all the way in Semi. It came with a ratcheting top and it doesn't always go back all the way. Maybe half of the rounds properly cycle.

Then I swapped in a non ratcheting top cover and it is doing the same thing, but bursting, probably because the ratcheting cover isn't holding it back, but this is my first Uzi and I don't know much about it.

How do I make the bolt go all the way back?

 

[Caverpete]

Is it open bolt operation or closed bolt?

 

[uzifan78]

Is it open bolt operation or closed bolt?

Open bolt. It seems like it isn't going back all the way and then falling on another round.

 

[slimshady]

The only difference between semi and FA is the sear pops back up in semi. If it is dragging on the bottom of the bolt it could slow it down enough to short stroke.

What ammo? Maybe some hotter stuff would work better.

 

[AKarms]

Is it open bolt operation or closed bolt?

Could be having a sear reset issue. Could possibly have a mix match of trigger group parts or sear hanging up on receiver. If you can’t figure it out and need it serviced give me a shout
Andrew
AK Arms

 

[Caverpete]

Could be having a sear reset issue.
Andrew
AK Arms

My thoughts exactly though my only experience is with a home build. To resolve a similar problem I had to open up the rectangular sear hole in the receiver a tiny bit with a jeweler’s file. Maybe pull out the bolt, switch the selector to semi auto and observe what the sear does when pulling the trigger.

Then again, the OP’s mini is not a home build so this really shouldn’t be the issue. Still have to eliminate the possibility of the sear hanging up on the receiver or not going down far enough during operation.

 

[slimshady]

From the description in the OP the gun functions fine in full but short strokes in semi. With the ratchet top cover the bolt doesn't go back far enough on semi to reset the ratchet and stays locked back instead of firing a second shot. With a non ratchet top cover it fires bursts in semi, likely because the bolt is not coming back far enough to catch on the sear. Assuming that info is correct.

Unless it is also short stroking in FA and he is just not noticing the extra round or two after releasing the trigger, the only difference would be the sear adding friction during semi cycling. The first step would be to remove the springs and see if the bolt freely moves back and forth under it's own weight with the non ratchet cover and the trigger pulled in FA. If it doesn't then he needs to correct the tight spots.

If it does move, then muzzle down pull the trigger in semi and hold it, bolt should drop. Raise muzzle, bolt should fall fully rearward. If it doesn't or takes a substantially higher angle than FA to get it to move some polishing is probably in order. Hotter ammo may cure the issue without further action.

 

[uzifan78]

From the description in the OP the gun functions fine in full but short strokes in semi. With the ratchet top cover the bolt doesn't go back far enough on semi to reset the ratchet and stays locked back instead of firing a second shot. With a non ratchet top cover it fires bursts in semi, likely because the bolt is not coming back far enough to catch on the sear. Assuming that info is correct.

Unless it is also short stroking in FA and he is just not noticing the extra round or two after releasing the trigger, the only difference would be the sear adding friction during semi cycling. The first step would be to remove the springs and see if the bolt freely moves back and forth under it's own weight with the non ratchet cover and the trigger pulled in FA. If it doesn't then he needs to correct the tight spots.

If it does move, then muzzle down pull the trigger in semi and hold it, bolt should drop. Raise muzzle, bolt should fall fully rearward. If it doesn't or takes a substantially higher angle than FA to get it to move some polishing is probably in order. Hotter ammo may cure the issue without further action.

I was hoping there was a known way fix. I’ll look at your tios and report back. Thanks.

 

[AKarms]

From the description in the OP the gun functions fine in full but short strokes in semi. With the ratchet top cover the bolt doesn't go back far enough on semi to reset the ratchet and stays locked back instead of firing a second shot. With a non ratchet top cover it fires bursts in semi, likely because the bolt is not coming back far enough to catch on the sear. Assuming that info is correct.

Unless it is also short stroking in FA and he is just not noticing the extra round or two after releasing the trigger, the only difference would be the sear adding friction during semi cycling. The first step would be to remove the springs and see if the bolt freely moves back and forth under it's own weight with the non ratchet cover and the trigger pulled in FA. If it doesn't then he needs to correct the tight spots.

If it does move, then muzzle down pull the trigger in semi and hold it, bolt should drop. Raise muzzle, bolt should fall fully rearward. If it doesn't or takes a substantially higher angle than FA to get it to move some polishing is probably in order. Hotter ammo may cure the issue without further action.

I don’t disagree with anything you said except hotter ammo. Hotter ammo might make it work but it’s not a “cure” the uzi should be able to cycle regular target rounds with no issues.