Built an Uzi, possible sear trouble

[Historian]

Hello everyone, I recently decided to build a semi auto Uzi and until now I've never held or fired an Uzi so I'm not entirely sure what to expect. The first issue is that when I try to pull the bolt back it gets stuck like something is blocking it. If I keep pulling it then it will take a moment, get past a certain point, and then be a little tight but otherwise a consistent pull. I can rack the bolt repeatedly after this without any issue, until I pull the trigger (on an empty chamber), and then the issue restarts.

I have also tried taking the top cover off and just using my finger to pull back the bolt and the issue persists. Looking at it, it seems that the issue is a problem when the firing pin assembly is forward. When I muscle the bolt back it locks the firing pin assembly to the rear and then I can rack the bolt no problem.

I took it to the range once and mostly worked. The only two issues were occasional failure to feeds (which I'm assuming is just part of a break in period) but sometimes the firing pin assembly wouldn't lock back after firing a round. As a result I would need to rack the bolt, eject whatever round was chambered if one was chambered, and proceed as stated above.

Looking at the insides I've also noticed friction marks around and to the rear of the sear. Do any of you guys have any advice/suggestions? If you want more info or pics let me know and I'll help as best I can.

Edit: Also, if I hold down the trigger then I can rack the bolt without issue.

 

[chipster]

New US made Sear or Ground up FA Sear?

 

[Historian]

Modified FA sear

 

[chipster]

I presume that is your problem. Looks like this can be a tough part to get these days, but I presume there will be a run soon.

 

[Historian]

I don't suppose you can narrow it down to what about it is causing the problem? It still seems strange to me that I can avoid the problem by holding down the trigger when pulling back the bolt.

In terms of getting a new US made sear, yeah I've been on the lookout. Unfortunately the only option I've seen for the last 6 months was a few weeks ago when US barrel offered modified FA's.