Saw an Dan Wesson shooter at the range, he had a .375 "super magnum" gun.
Monster rounds, silly recoil.
Says he had to spend a few months finding brass and bullets that would work with the little published data. He had some real 375 brass, and some that was formed from cut down 30-30 winchester casings. He let me shoot one round, and its a hell of a load. .375 caliber flat nose 200 grainer.
I guess they were developed for long range steel shooting.
Hell of a thump in the recoil area, though!