My UZI has a problem. Turns out that some of them had minor warpage in the stamped receiver, such that the barrel points uphill a bit. It seems to have been caused by iffy stamping dies, but solid information on the problem is scarce. Whatever the cause, it's just enough to cause the telescoping bolt to contact the barrel. There should be no contact at all.A problem with this is the friction between those parts apparently slows the bolt's momentum enough to cause ejection problem, which has indeed been a problem with the gun. Finding a smith I trust to not hose up a title II weapon has not been easy.
Looks like the fix involves removing the old trunnion and welding in a new one, plus a little tweaking of the receiver so the barrel is truly parallel to the receiver, and then reparking. All for only $650. Ouch. And I'm on a waiting list.
Here's what a trunnion looks like:
Apparently, this not that uncommon. I think this does a good job of illustrating how the cost of a machinegun has far less to do with quality than it does with its place on the long-closed registry.