I have a 26" Hart barrel heavy 6 flutes. It's on a FN action "SPR" same thing as a pre 64 Winchester model 70. I'm going to try 65-75 grain bullets after I break this barrel in with these 60 grain Hornady's Custom loads so I'll have some fire formed brass to work with. I guess all I can do is wait and see what shoots the best group. Ah by the way I'll be shooting small game, prairie dogs and other varmints as well as paper targets. Anyone here have some different load data they would like to offer up?