Then anything will do. If you were going to be taking 600yd+ shots, then you might want to invest in a .5MOA shooter..... but for 300yds varmint shots (3" groups would be fine) then I would just get what suits you. Might conside a 20" rifle length if a lot of your stuff is going to be long shots, for more velocity. DPMS makes some nice, accurate barrels.