I believe in keeping it simple. About the only thing I use shotguns for now days is 3 gun. I use an old Remington 870 Police Riot gun with an 18 inch smooth barrel.
In three gun, you don't shoot that far, you are required to shoot bird shot, slugs and buck shoot.
Like I said, I keep it simple, I use WW AA Hulls, AA wads, and a Mec 1 oz charge bar.
I load 1 oz of 8 shot, and Lee's 1 oz slug, and I use a Lee round ball mold that makes .319 balls at 48 grns, which I stick 9 into the same AA hulls and wads.
Recoil is the same across the board, the buck shot and bird shot pattern plenty good enough for the distance we shoot, and I have no problem hitting an 8 inch circle with my slug loads at 50 yards (again, within the distances we shoot).
The only modification I do to the above loads is I use a magic marker to mark which shell is buck shot or slugs.
I have other charge bars for my Mec 600 If I decide to go bird hunting, but there aren't many birds around here. Or I have the set up for trap and skeet loading if I decide to get back into those games.
You really don't have to get all fancy with slug loading.
Some people deer hunt with shot guns, If I was to do that I have faith in my slugs, but I'd probably put a bit more powder behind my buck shot loads.