My gun never has shot much factory ammo. When I first bought the gun I shot some Winchester 150 grains Silver BT because no one at that time had much load data for the 300WSM. In fact I was rather disappointed with the accuracy of the factory ammo,(1.5 inches for 3 shots) so I started reloading as quickly as I could get dies and data. I started to realize how accurate this gun would shoot when I loaded some 165 grain Nosler Partitions in WW brass with RL-19 powder. This load would shoot 5 shots under an inch.. My results with the Nosler bullets led me to try some match bullets. I found that I could get great accuracy with 155 grain Sierra match and that is the bullet that my son in law shot the .25 inch group. Since then I have shot many Sierra match bullets,(155, 168, and 175). As for hunting bullets I found that I could get very good accuracy using 168 Barnes TSX bullets as well as the Nosler Partitions already mentioned.
What I found was the more I shot the gun the more accurate it became. I don't know if it was just the barrel getting broke in or that I was just finding better loads. Any way I am very pleased with the gun.