I understand now. Have you shot for groups with iron sights?
If everything you have shot is FMJ you may want to try a different bullet like 69gr Sierra Match Kings from Black Hills or Federal.
The truth is many production barrels are loose in the muzzle and spray bullets, the 69 SMK seems to work much better in those loose barrels.
The second check is borrow a scope from someone and try it just to narrow down the problem.
The 6.8 is the fastest growing cartridge and #1 choice for hunting deer and hogs with an AR15.
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