Try two things, less powder, and a different primer. I too use Win 748. Dirty stuff. 24.5 grains under Hornady V-Max 55 gr. bullets in a mixed bag of cases. 748 fouls the action in 200-300 rounds. Fun as ice cream to shoot the M-16 though. I didn't start shooting for groups until I got past the "Let-er-Rip" stage of five or six 30-round magazines. Most fun I have had blowing $50.00 in a L O N G time. After all, it's only money, right? Naw, its much more visceral than that...now I am getting quarter size at 200 yards for a 10 shot bench rest group and I AM STOKED. I did one string of rapid fire and the 2" group at 100 yards was a thing of PLEASURE. Good Luck!