Yes its useless it wouldn t matter if ballast in a 'Man of war'. But since you like ballance what does foreward dead wieght do for that ? .Re rifle barrels they Need to be heavier for stability . Of two guns rifle patched ball & smooth the smooth fireing shot with loads typically exceeding the fitting naked balls wieght are more stressed that with a heavier barrel. The rifleing isnt to do with strenght its to do with holding it steadier. and the spinning the ball . Rifleing is detremental to velocity & force. but the barrels are better suited to long ranges ,Whilst the shot gun needs be readily brought up to shoot moveing game or clays w ,h, y, Its thin wall stands more stress by the upsett of fireing of shot ( With a ball it can only fit round it's edges ). Ever notice the dimples on recovered shot ? ,ever try to place a wad in the muzzle then load shot & a top wad , Then try push it down? .Of course if you like lugging useless weight then fine but I don't and to me its Useless wieght .
Rudyard