In my experience I have found 10 and 8 bore ball and shot guns are built much different than a conventional shotgun. Rifling them is a bad idea. Pressure builds with lands and grooves. An 8 bore shotgun weighs 10 to 11 lbs, a Ball or jungle gun, smooth bore, weighs about 13, a Paradox 15 and a fully rifled 16 to 17. Yes, the charge determines a bunch and these figures are +/-. but the point is the difference is usually in the barrel weight. Be careful!!