I've got a 500 Max revolver; and out of my 5" barrel it will push 435's @ 1500 fps, 500's @ 1350, and 580's @ 1200. None of those loads are pushing the envelope -- I know of one 500 Max shooter who gets over 1600 fps from 450's in a 6" barrel. Those same loads in a rifle-length tube would probably pick up around 400 fps which would put them in pretty much the same class as "Marlin-only" 45-70 loads. It would be a neat rifle, but the 50 Alaskan probably makes more sense for those that don't have a 500 revolver.