IIRC the original was .45-70-405, 70 grains BP behind a 405 grain bullet

The 577/450 with 85 grains behind a 480 grain bullet is more powerful, it certainly kicks more with the steel butt plate!
Having read most of the mid to late African hunting books the 577/450 was occasionally used on all game including elephant, even after the introduction of Nitro powders

TH44