as in smooth bore do you mean no choke or anything?? most 18inch barrels come on riot guns....(law enforcment/tactical shotguns) and most come with a straight cylinder choke....that will not throw a turkey pattern for beans after about 10yards.....be better off throwing the shell at the turkey by hand....all shotguns are "smooth bore" unless they have rifled slug barrels.....which will not be good to shoot shotshells from....if the 18 inch barrel takes chokes...get a good turkey choke for it....extra full super full....they come by many names....and pattern it with turkey loads and see how it shoots....i shot a 21 inch barrel on my turkey gun....loose a little velocity....but i like the lightness and manuverability with the small barrel.......