Drillings are generally designed for Breneke slugs.
A few thoughts:
: Roll crimp formers are available from Lyman & probably Lee.
: Brass cases are of larger capacity due to thinner walls, but should allow light star or stab crimping. They may require annealing frequently depending on the amount of crimp. They are expensive. Proper size wads for brass cases may have to be made due to larger size.
: I'd try "Old West Scrounger" for 16 bore brass and Breneke slugs and wads.
:Hope this is helpful.