I'm at the local indoor picking up my brass, when i see primerless 9x19 and several VERY flat primers with flowback. I remember the rental UZI being in/near that lane and matched primer flow with the UZI bolt face. Are UZIs known to have tight chambers? Do they get dirty and require cleaning? Aside from the length, bullet weight, powder charge (& argueably primer choice) what could cause this? I was able to pop primers out with my fingernail. Thanks for insight.