My rifle sports a PSA Premium M4 upper and it's been trouble free and accurate for two outings. Between Both outings I've shot a mix of Lake City 55GR 100rnds, PMC XTAC 62GR (40rnds), PPU 69Gr Match (40rnds), TulAmmo 55gr (80Rnds), and a handful of old hand-loads I had hanging out in the .223...