No issues at all and it sounds like you are getting good groups from a semi auto Carbine. You want tighter groups get a bolt action.
NCH
1/9 twist should be good up to 69 gr bullets and depending on the barrel may still shoot 75gr ok too.
Don’t remove the firing pin and put the carrier in the upper again…you’ll have a not so fun situation on your hands.
What happens?
The firing pin hold the cam pin at the right angle. Without it, the cam pin can turn the wrong direction and lock your BCG up tight in the upper.
Oh, ill not do that again. Thanks!