I have 2 ARs, std 16” barrels one is 1:9 other is 1:7
My most accurate load is 62gr Sierra SP with 24.5g Varget, CCI primer, 2.25 OAL
3/4” groups @ 100yds off a bench rest.
Best groups with factory ammo was hornady match bthp which managed 2” groups
All hunting rounds I tried 3” was typical out of either gun.