I zeroed my rifle at 100yds for hunting with the winchester .308 150 gr PowerPoints. I then started to set my rifle up for some LR a few weeks later by switching to the federal gold medal match 168gr sierra match king bthp's. The fed gmm started grouping 8" to the left and 3" low, but it was a tight group. I thought stuff might have loosened up on me, but I threw a 150 gr power point in to see if I still had a zero for it and it hit dead center and split the cross. I have since brought the fed gmm to .5" moa and am not having any zero issues. My question is why such a huge deviation between rounds? 8" to the left and 3" low is pretty drastic. Barrel data is 24" 1-10 twist chambered in .308.