That twist should shoot a lot of bullets pretty well. for 300 yards, I'd try the Berger 73's, Sierra 69's, etc. I have never got the 77's to shoot exceptionally well unless a faster 7" twist. I'd expect to get 1 1/4" to 1 1/2" groups at 300 with those bullets. If your rifle cooperates with your loads - you might get much better - maybe 3/4" if you are lucky. I cannot recall not being able to ultimately get 1/2" MOA out of a quality bolt gun when handloading.It's sounding more like I would be happy with a rem varmint or tikka varmint and drop in my stock of choice. I'm happy with 1/2 moa at 100 . Would you expect at 300 yards ? The rem varmint with 26in barrel has a 1in8 twist and should shoot 77g smk I'd think