I don't know the ballistics for my pro-hunter 500 S&W 20" barrel (I haven't cronyed it yet), but I do know what it did to 2 deer this fall (devastating wound channels, and complete chest cavity pass-through diagonally on both animals). I shot 3" groups at 100yds using a 4.5 power scope.
My hand loads are as follows:
Hornady brass
Winchester Magnum Pistol Primer
18gr Tight Group (luv it, burns very clean)
350gr Hornady XTP bullet (light roll crimp for single shot barrel)

And no, it didn't do a bit better job than my pro-hunter 50cal. muzzle loader barrel that shoots 3 quarter inch groups at 100yds. But---I didn't need an excuse for buying a new barrel or trying a new caliber. The 500 Smith is definitely the best choice to hunt with in rainy weather. What a "BLAST"!!!!