remington slugger foster slugs are slightly oversized so i personally wouldnt go tighter than an IC for those, but the accuracy of most other foster slugs benefits from the slightly tighter choke. same goes for brenneke style since they are hardened.
you have to shell out (no pun intended) for a variety of different boxes of commercial slugs and hit the range and see which works best in YOUR shotgun though.
Most slugs other than sabots are oversized to accomodate the variety of bore diameters. Some are hollow on the rear end to allow conformation to size of the bore and make a seal so they will not just bloop down and out of the bore. Some have some sort of wad attached to the bore to accomplish the seal.
Which choke? Much like trying several commercial slugs to see which work best, one should try their slugs with a variety of chokes to determine best.



















































