"QUOTE" Lot of deer hunting guys want less recoil and more speed with
a flatter trajectory that speed and
a slimmer more streamlined 50 cal slug in
12ga sabot can give them. And a 4-500 gr 50cal
slug at 2000 plus fps will do credible job. "QUOTE"

Yes - I am aware of what they are doing - I just don't understand - well, never mind -
A 400 to 500 gr. .50 cal slug should have a 24" twist or perhaps a bit faster, but not needed. Apparently, PacNor makes a 22" twist 12 bore barrel. I wanted an 80-85" twist with 5-6 thou rifling, but am having difficulty finding one.