The .450 BP Express used several loads, one of which was a 270gr. copper tube nosed bullet at 1,900fps, I believe. A Ruger or Browning lever gun easily exceeds those ballistics and so will a Trapdoor Springfield even though it has a lower pressure ceiling. Current factory load of 300gr. at 1,850fps is virtually identical to the 'factory' 300gr. BP loading for the .450BPE.