If it is 1 in 12, Winchester White Box ammo with 45gr bullets seem to work best. Hodgen puts out a magazine size reloading manual. In it they give the Winchester factory duplication load. I use that load for my old Handi with the 1 in 12 twist. The newer Ultra has a 1 in 9 twist and I like to load and shoot heavier bullets with it. (It's an Ejector with 1 in 9 twist, so that old rule about ejectors being 1 in 12 and extractors being 1 in 9 is not always correct. You need to check it with a tight patch and cleaning rod.