I talked to the man at Starline, where 460 Rowland brass is made, and he said that the 45 Super brass is the same design, just a hair shorter. He said that the really high pressures of 460 Rowland and 45 Super were for good chamber support guns. He said the +P brass acurally has a thicker web and is for guns with poor chamber support.
Clark Guns will not sell you a 460 Rowland pistol or converstion without a reoil compensator. Even with the heavy slide, heavy spring, and recoil compensator you are going to get slide slam.
My 42 pound spring set cuts out the slide slam at 10.3 gr AA#5, but at 14.4 gr [460 load], there is plenty of slide slam [but not enough for me to flinch].