At the 400-450 you might have been resting the barrel against the backpack and the barrel just cleared resting on it at the 500. I think with a pencil barrel, upward pressure on the barrel would throw a shot significantly high.
Farmer Brown
2021-02-26 06:38:50 +0000 UTC
seems to do fine but man that looks and moreover the shortish handguard... seems an awful high package, too. weight must be nice though. don't recall. another ar18 based piston multible lug?