Bullets tumble upon exit from barrel.

[GeeRam]

which ever way you look at it tumbling projectiles at 50 yards I'd say your barrel is stooofed...

Does seem the more likely scenario in the circumstances.....given using PPU ammo, which is the best available commercial ammo, other than finding some genuine milsurp Mk.VII which is not easy......and the fact that it was a $400 rifle, which in this day and age, is somewhat cheap for a No.4?