I have experienced really, really poor 5.56 accuracy from:
1. Lightweight barrels that heated up; in my case Mini-14's
2. Lightweight bullets through 1:8 twist barrels on AR's
You've got both
I agree you should rule out loose optics, muzzle crown and a LOOSE FLASH HIDER (a big problem I have experienced) but if one bullet weight is shooting well and another is not, they are probably just a bad match.
I keep a range log but I am considering putting a 3x5 card on the stocks if some of my rifles to help me keep all of this straight.
1. Lightweight barrels that heated up; in my case Mini-14's
2. Lightweight bullets through 1:8 twist barrels on AR's
You've got both
I agree you should rule out loose optics, muzzle crown and a LOOSE FLASH HIDER (a big problem I have experienced) but if one bullet weight is shooting well and another is not, they are probably just a bad match.
I keep a range log but I am considering putting a 3x5 card on the stocks if some of my rifles to help me keep all of this straight.