Forgot to mention, my current lead slinger is a 1970 Marlin 336 in 30-30 with Microgroove rifling. Shoots wonderfully with cast, but I took the time to lap it and make sure the tightest part of the bore is the muzzle. Bullets are sized to .310, bore measures .309 at breech and .308 at muzzle. Scoped it with a Leupold Vari-x II 1-4 power.