NFA Dealer Sample UZI...problems

[johnlewjohn]

I just finished my first Uzi...I have a few questions...I am having trouble with ftf's and no-fire "clunks"...and then sometimes it runs like a charm...I have been told that my feedramps could be a problem or something may be draging and causing the bolt to slow down enough to hit too soft...I made a registered full auto open bolt in a semi receiver....turned down the barrel and made sure the sear pads dont hang up on anything...
with no mag in the well I can cycle the bolt all day and nothing appears to be catching on the bolt...it moves very freely.
Obviously with an open bolt I cant really check the feed cycle on a live round...at least not without scaring the chickens...but I am wondering if it may be a mag problem...I only have one mag with 4 more on order...any ideas of what to check would be greatly appreciated....

Thanks

John

 

[RoverDave]

Are you sure the bolt doesn't hit the top of the barrel restrictor ring? It doesn't look like it from the photo but an unmodified FA open bolt typically will hit it.

 

[johnlewjohn]

Are you sure the bolt doesn't hit the top of the barrel restrictor ring? It doesn't look like it from the photo but an unmodified FA open bolt typically will hit it.

Yes I had to remove material on the bottom side of the bolt to clear the ring along with machining the slot in the side to clear the bar...at first I thought it wasnt going far enough forward...but the front of the bolt is hitting the back of the trunion...so that satisfied that theory, unless the trunions are different between the semi and full...

Still thinking.


John

 

[amphibian]

Are you sure the bolt doesn't hit the top of the barrel restrictor ring? It doesn't look like it from the photo but an unmodified FA open bolt typically will hit it.

Good call!
The exception would be a Group Industries SMG bolt. The ones I've seen were all "pre-clearanced" to go over the restrictor ring.
Do you know what the origin is of the bolt you're using? The Group bolts usually have a "G" stamped on the left side.
You have a nice semi feedramp so I doubt that is your problem.
Have you checked the clearance you have between the top of your bolt and the bottom of your topcover?
Use a feeler gauge. You don't want it to be less than .005".
You can also remove the recoil spring and w/ the muzzle pointing up, make sure the bolt freely goes back when pulling the trigger and likewise goes freely forward when pointing the muzzle down.

 

[johnlewjohn]

DIRTY CHAMBER?

I was wondering if a significantly dirty chamber could cause feed failures and possibly be slowing down the inertial energy of the bolt causing a misfire...
out of 125 rounds of WInchester White box I had 4 misfires and failure to feed...if I get chance I will take a shot of the primer hits and post em....

still trying to get to the bottom of my problem

John

 

[dsspro]

Is that the one I saw you with over at bernies.
call me sometime, I can take a look at it firsthand. plus I have a few different uzis we can test to check the parts.

Aren Dela
612-325-0314

 

[chrisp929]

bolt may be hitting the sides of the barrel ring .. i say .. chuck the reciever up on a mill and shave of several thousanths off each side of the barrel ring ..

 

[jwp]

put empty mag in well w/o the foillower and see if dragging on feed lips
couple of my mags have worn the front edge of the lips and now work fine but some ftf in the beginning

 

[johnlewjohn]

Feed ramps....

I fixed part of my problem...the grip frame was not straight coming off the receiver...causing the mag to be slightly cocked sideways and the bolt would rub on the feed lips of the mag and in one instance would stop it totally...I took off the grip frames and put it in a vice and straightened the lower so the mags sit in the receiver straight...the bolt does not hit any of the mags at all now...

So I thought it was fixed and tried shooting it again and I am still having feed troubles...the rounds are not smoothly going into the chamber slowing the inertia of the bolt down to non-ignition primer hits and sometimes stove piping into the chamber or jamming it on feed...

Is there a difference between the full auto and semi auto feedramps?

I have posted a detailed pic of the feedramp and chamber end of the barrel... I am really miffed at what would be causing the problem...


JOHN

 

[johnlewjohn]

Feed ramps....45 vs 9

this was the other thing I was thinking of...the receiver was orignally marked 45 acp and 45 acp only...it did not have all three calibers on it...would that make a difference on the 9mm as far as the feedramps go?

John

 

[RoverDave]

There is a difference between the full auto and semi auto feed ramps but generally the semi-auto ramps are considered more reliable and people sometimes pay Vector extra to have them installed in their full auto. Typically this is done with just the ramp and not the attached barrel restrictor ring.

There's no difference in the 9mm or .45 feed ramps.

 

[Vegas SMG]

Could be a worn recoil spring that simply is too tired to properly strip, chamber, and fire a round. Sometimes the really simple things are over looked.

I've shot many thousands of rounds in my UZI and the spring seems fine, but I did have the same problems as you with a M11/9 at about the 5,000 round mark and a new recoil spring cured my issues.

 

[drw]

I would like to see a picture of the bolt face to see if it has been clearanced for the restrictor ring. There are no apparent marks on the restrictor ring but that could be due to the two surfaces being square to each other.

 

[johnlewjohn]

Cyclic speed variations...

I also noticed that when it did seem to half work and I was able to get the gun to run like it was kinda supposed to that the cyclic rate would speed up and slow down...I would imagine it was because of the feed variations...

John