I had the same issue with an M70 in 300WM. I really wanted to shoot 180s and spent a lot of loading bench and range time trying to make it happen. No matter what combination I tried it would not shoot the 180 grain bullets (Partitions, Ballistic Tips, and Accubonds). On a whim I tried the 200s and presto! Completely different rifle. Great results with both Partitions and Accubonds. I settled on IMR 7977 which shoots right at 2800 fps for me out of a 26" barrel.