I have a bolt-action 450 Marlin built on a short Rem 700 action and I can easily get 4000 ftlbs of muzzle energy with bullets ranging from 250gr to 350gr and I probably could with the 400gr bullets except the recoil is stiffer than I want to put up with. I think they would work fine for leopard and lion and I think with a proper bullet it would be OK for buffalo...but not for elephant.