OK here is the deal.. I have been thinking of building a heavy short varmint rig using a savage action with a no taper barrel with a laminated stock and an 17inch barrel 6BR. Max range would be 400 yards I would say. How much barrel do I need to burn up all the powder? Also what twist would I need for 55 to 68 grain pills? Would this even work out to 400 yards? But I would think that most shots would be under 300.