Last fall I semi-panic-bought a Sport II, slapped on a Romeo5 and zeroed at 50yd with cheap Wal-Mart Federal .223 (
#BP223BL ). Last group after zeroing:
Fine. Then I continued with some XM193 headstamped "FC 17" from (I think) a Natchez loose bulk case:
Something was wrong with me or the gun or the ammo so I quit for the day. A couple weeks later I shot at an indoor 25yd range (hence the low POI). I alternated between the
#BP223BL (right) and XM193 (left) going from bottom to top, every 10 rounds. My groups with the .223 tightened while my XM193 groups slightly expanded:
Is it possible XM193 (or at least my lot) gets less precise with barrel temperature while other ammo does not?