What I meant by the above statement, and should have clarified, is that you can duplicate that velocity (approx. 1,650fps) with a 420gr. bullet in the weaker actions, indeed, 1,700fps is available, with appropriate powders, of course.
I am currently shooting just such a load in my 35" bl. Sharps .45/60 (1.9" case), a 400gr. Jacketed at 1,750fps using benchmark with large BP firing pin, without any pressure problems. With full power black powder loads, it will show some primer cup movement due the angle of the large pin, however the smokeless load shows less expansion and no cup movement. This is a load I'd use in about any .45/70's, 2.1" case and should develop between 1,550fps and 1,600fps with the jacketed bullet. Cast bullets will give approx. 100fps more velocity for the same load. Hodgdon's Annual Manuals show the loads and pressures given.