RE: Mossberg 500 Bantam
Yup, what he said.
You will probably get the best accuracy with a fully rifled barrel, cantilever scope mount ans sabot slugs. But that amounts to a few hundred bucks.
You can do just fine within 50-75 yds with a smoothbore barrel and foster style (rifled) slugs. You really need to concentrate on a consistent sight picture if you have only a front bead, but it can work.