Empirevr,

The 577/500#2 has a case length of 2 13/16". The 577/500 magnum is 3 1/4".

The standard load of the day was 130grs. powder w/ a 340gr. or 380gr. bullet. The one I own regulated nicely with this load.

It is basically the same as a 500 3" BPE, although I have found it easier to load with todays black powder because of the increased case capacity.