Well to start a rifled barrel will increase your gun's accuracy dramatically by putting a spin on the slug or sabot. A lot of states have outlawed buck shot for deer it was a short range load anyway. using a standard barreled shot gun limits your effective range to about 70 yds and sometimes accuracy is very poor. Rifled barrels will increase the range to 150 yds or so scoped. You really need to shoot various slugs to see which one gives you adequate accuracy. There is no need use to shoot a sabot slug from a non-rifled shot gun as it will not impart a spin to the slug. Try standard lead slugs in a smoothebore.