The saboted slugs require a rifled barrel to stabilize the slugs. The first to hit the market, back in the 70's were the hour-glass shaped ones from BRI.
: Even from a rifled barrel, they'll show tipping when going through a target at 50yards. This idicates they weren't stabil and would not travel in a straight line after impact.
; For straight-line penetration from a shotgun smoothbore, I found .684" round balls, either held in a thin denim patch(as in a muzzleloader) loaded in a shotshell or set between shot-cup bases shot the best. When cast from WheelWeight metal, they were terrific and shot into 5" at 50yards.
; For a non-choked gun, I'd use .715" balls (Lyman mould) that run 545gr. in pure lead, or 520gr. in WW metal. Held betwen the bottom cups of a shot-cup, they'll generally shoot very accurately at close range.
; I used data for 1 1/4 oz. and 1 3/8oz shot. SR4756 and SSR7625 seemed to give the best results. You can easily get 1,500fps, which matches the light, 5.5 dram Afrcian 12 bore RB load, with very light to moderate recoil. On the other hand, you can load Black Powder for Rball loads in either the light or heavy load which was 7 drams. Both shot well in my shortened sideby side.
; The 'heavy' load will apparently exit an Indian Elephant's head quite easily and can be duplicated with smokeless powder as well, for lighter recoil than the BP loads.