Umax 44 Mag Cowboy load is a 240 gr flatpoint lead bullet at 750fps, compared to a mid-range lead Remington at 1000fps, or a full house at 1200 fps. The 'magnum load' is almost 2x as fast as the cowboy load.
"Cowboy loads are usally limted to well under 1000 fps by the Single Action Shooting Society rule book, you could load them hotter by hand and still make the rules. 240g @ 750fps is nothing to sneeze at.