SO, I bought a Century UC9 for CHEAP because the previous owner said it would fail to feed from time to time. I took it out to the range and it runs 90%-95% depending on the ammunition. I have been running the usual diagnostics but I have a question.

When I measure the gap between the bolt and the top cover should the gun be "cocked" ready to fire (if it were loaded) or uncocked in the fired position before the bolt would begin to travel rearward? The gun passes the gap check in the uncocked (fired position) but I cannot even get a .002" feeler gauge between the bolt and top cover in the cocked (ready to fire) position.

Thank you all for any help or suggestions you can provide  

That's because the striker is trying to "ride up" on the sear, due to the angles involved and the recoil spring tension. It's pushing the bolt up with it. The only thing stopping them from going up is the top cover.



I'm unfamiliar with your test, but take out the recoil spring, tilt the muzzle down a bit and let gravity pull the bolt all the way forward, and the striker forward to the sear (ready-to-fire position), then repeat your test.

Failure to feed is 99% of the time a magazine issue. If it's running fine 95% of the time, I wouldn't be surprised if one of your mags isn't hanging up somewhere. Try to figure out which magazine is causing the problem. Then take that mag apart, clean, and inspect it. It may just have some crud in it, or perhaps a bur somewhere it's hanging on. Also, keep in mind that the Uzi was designed to use rather hot loaded ammo(as I recall the Israeli issued ammo was hotter than +p), and even the semis seem to run better with warmer stuff(since they are still recoil operated, though obviously not open bolt). So you may find it runs better with one brand or another if it's slightly higher pressure.

Failure to chamber is something else entirely, though again you may find running warmer ammo might help, simply because the bolt will be being moved more vigorously.

At least this is what I have found with mine. It will run decently with just about any 9mm ammo, but if I know I'm going to run it hard(or it's going to get nasty) I use warmer loads in it.

If it's running 90-95% of the time, your gap is fine. From what I understand if there is an issue there, it won't run much at all.