It’s much better now, definitely an improvement, but still having an occasional problem not fully feeding (about 1-2 rounds per mag now, instead of several). Had the same with 1-2 rd issue with the REM 115gr, but again, no problems whatsoever with the reload Super Vel 100gr. Blitz. 100% function.
Nobody noticed that you answered your own question.
My UZI started running like crap, so I took it to the range and changed every part, one thing at a time. There is a thread about it here.
The two big culprits were a dead extractor and weak ammo.
The extractor looked fine, but it lost enough of its springyness to cause FTEs.
UZIs like a lot of recoil energy. IT'S IMPORTANT. Notice how UZIs don't throw empties a mile like some guns do. That UZI mechanism is eating up a lot of energy.
I had been loading softball ammo to save powder and that was 90% of the problem with the gun.
SOME FACTORY AMMO IS WEAK AF. If you chronograph factory ammo, the velocity varies amazingly, even in the same brand. LIke Speer Lawman is 100 fps slower than CCI Blazer for the same bullet weight.
Remington UMC is a complete joke, the bullets barely dribble out of the end of the barrel. This is well known among shooters. Seriously, load half a mag of Federal and then top it off with Remington and do a mag dump. You'll be astonished by the difference in ROF.
Muzzle energy for Super Vel Blitz = 375 ft-lbs
Muzzle energy for Remington 115 = 335 ft-lbs per their website, probably in reality it's more like 250 ft-lbs.
Muzzle energy for Federal 124 = 365 ft-lbs.
I first discovered this Remington thing when I had a MAC M11/9. It ran slow on Remington ammo. The gun was literally chugging like a M3 grease gun. And I was stupefied, until I mixed a mag of Remington with some WWB and it went from chugging to brrrrrrrrrrrrrrtttttttttt.