use improver cyl. choke tube for slugs. dont know about buck shot it is illeagal in ohio. if you want the best results spend a few bucks and buy a riffled barrell. you wont be disappointed. i shoot a mossberg 835 12GA riffled barrle and shoot winchester platinum series slugs. open sight and can group in a paper plate at 100 yrds no problem. as for your 20GA i hunt with some guys who have kids old enough to hunt and same configuration as my 12GA riffled barrel good slugs and they will stop a deer just as well if you hit where you are supposed to hit.