i use the hornady sabot slugs in my 20 gauge remington 870 rifled barrel.
my buddy uses normal rifled slugs in his mossberg 500 w/ rifled barrel and has good accuracy with that combo also, just have to clean it more then with sabots. can still shoot 30 shots a day no problem though...
box of 15 for 10 bucks for normal slugs
i get a box of 5 for 12 bucks... i only use mine for hunting, use smooth bore barrel and rifled slugs when target shooting