Having issues with the bolt rubbing on my full size UZI build

[ljborns]

I'm working on my full size UZI, and have run into an issue with the bolt rubbing. I bought the repair section, and a kit from Numrich. I had a friend weld the ends of the receiver on, and everything went together pretty smoothly. I did notice that when I put the top cover on, the bolt would move smoothly from the rear of the receiver all the way forward until about 1.5" from the trunion. It would then bind up and stop going forward. Attached is a pic with the cover removed, but this is about the point at which the bolt would bind with the cover on. You can see where it would stop in this pic.

 

[ljborns]

I know that top cover doesn't sit flush on top of the receiver, and that there should be some room between the top of the bolt and the bottom of the receiver. Here is a side view of the receiver and you can see the bolt sitting above it by just a little bit. This is with the bolt all the way back in the receiver.

 

[ljborns]

So what are my options? I thought of two things. One is to grind away some of the material that is on the two ridges that run down the underside of the top cover. As you can see from the third pic, the top of the bolt is obviously rubbing on those two ridges.

 

[ljborns]

My other thought is too grind down the top of the bolt a little bit to remove some material. Any suggestions?

Whats odd is that I only had the issue with the bolt binding at the front of the receiver, when it was just the bare receiver with the top cover on. Once I installed the grip stick, foregrip, stock, etc, that's when the bolt will not move throughout the receiver at all. Its binding up pretty bad. Here's a pic of where I'm at so far.

 

[Funner]

Hey. Hope you figured out your problem.
Its very possible that the bolt is rubbing on the barrel support ring on the feed ramp. Without the lower or top cover on, flip the receiver over with bolt in and slide bolt forward. While looking through the mag hole, a flashlight will help. Observing the bolt to restrictor ring contact.
May be it.
Good luck

 

[Funner]

O yeah. No recoil spring in to feel resistance.

 

[Funner]

Also what bolt are you using. McKay, d&d, etc, semi auto bolt?

 

[Funner]

Or simply looking from the top/side down through ejection port area. All with receiver sitting normal (not upside down). Seeing if the bolt rubs on the ring..
It may or may not be your problem. But I have seen this before.
Good luck.

 

[ljborns]

Thank you for the suggestions. What I ended up doing was using a grinding disc to take a small amount of material off the top of the bolt. I knew I was taking a chance at messing it up but it worked. Almost... The only problem now is the tolerances are too tight between the bolt and the top of the magazine. With a mag in, if I rack it, the bolt goes forward but binds and stops about 1/4" from where it should stop at its most forward position. I can reach through the ejection opening and slide it forward pretty easily at that point. If I rack it with a mag out the bolt goes all the way through its range with no binding.
I ran a few rounds through it and noticed some scuff marks on the sides of the mag from the bolt. I'm hoping when I run a few boxes of ammo through it, everything will loosen up some.

 

[ljborns]

As far as the bolt, it is a SA bolt I got awhile back off of gunbroker but I'm not sure of the brand.

 

[Opelgt]

Can't tell from your pics. Was your repair section welded below the top of the front trunnion? Another words, is the top of the repair section flush with the top of the front trunnion?
Also, are the tabs still in place by the rear trunnion?

 

[ljborns]

Yes, its welded straight across with the tabs in place on the receiver for the top cover. What I ended up doing is grinding a small amount of metal off the top of the bolt. I kept cycling it numerous times, and then looked for marks on the top of the bolt and ground those down a little more. I'm guessing that when the front and rear sections were welded on, they were a little bit too low, causing tight tolerances between the bolt and top cover.

After that, it shot good; it had a few FTF, with light primer strikes, so I need to work on that to see what the problem is.