When starting loading balls in my 12 bore sxs, I started with using WAA12White wad bases as a gas check, then a fiber wad and a plastic base, cup-up under the ball to centre it in the bore. I also started with loads for a 1 1/4ounce shot charge using a slow burning shotshell powder, just to be super safe. It was super safe as the ball was only 1 1/8th ounce and I was able to safely increase the powder charge to get 1,500fps with the ball.

If loading them like they do on U-tube like TAOFLEDERMAUS and some others, they simply pull the shot load and stuff in whatever slug they are testing. I did not do that, as the fast burning powders used in most light shot loads, did not give me the peace of mind, that slow burning powders and low printed pressures gave me. Mine had standard star crimps.

I have noted, of late, that the above named lads are now hand loading for some of the slugs they are sent to test from around the world, using 'Steel' of 'Longshot' powders which are more suitable for these type of loads.

I have no slug or ball data for these.

I refer anyone who wants to try shot loads with balls or slugs, to buy a Lyman book, study it and use due care when developing your loads.

If not understanding what and how you are doing this, don't!