I was shooting 208 ELDms from my new 300 Mag. C.O A.L 3.500. 79.5 grs N570 Fed 215 primers. I was getting over MOA at 100yds, and the EXT spread was 100FPS(2,839-2,942) and SD about 60. That isn't very good. Even so, I could hit the gongs at 300-400 yds. 10" rifling twist Bergara B-14 HMR. What could be the cause?