Target distance 100 yards, Colt AR 6724 24" 1 in 9 twist SS 5.56 barrel

Upper left 24.9 gr Varget 69 SMK velocity 2940 SD 13

Upper right 25.1 gr Varget 69 SMK velocity 2965 SD 18

Lower right 25.3 gr Varget 69 SMK velocity 2988 SD 12

Lower left 25.5 gr Varget 69 SMK velocity 2986 SD 17 ???

Trying to read group shape, and think that the more dispersed appearing lower right was best? The fault in these groups was the poor Brass quality I choose FC Am Eagle assorted mixed lots.

Obvious plan is to try again with a fresh start. Comments please.