Shot guns are meant to fire multiple Pellets ,called shot. Short range, scatter and lots of soft tissue damage. Plain or sometimes choked barrel.
Rifles have "rifling" A slow spiral of flutes to spin the Projectile for accuracy. Snipers rifles have heavier Barrels. Pistols don't have range accuracy Barrels are too short. If the Point is filed off the projectile will do more damage. Some times called dum dums. These shotguns were firing solid material so presume they were for being more Lethal. Nev