I make my .303 from 7.62x54R, both are .311". I pull the bullets and use with the powder.. 43 grains gives exceptional accuracy in my No4's if I'm on form.Where do you get your ammo? I have a #4mk 1* but its just a wall hanger at this point because .303 ammo is too expensive and too hard to find to make it worth it to me.
5 shot group at 110 yards, under 3/4". 3 shots at exactly the same POI