Taking a deer cleanly with a single shot (with no chance of fast reload) from over 20 yards away is an expert's business, to be sure! I'm extremely impressed. That's absolutely my limit for shots with my heavy .44 Mag loads out of my Super Blackhawk, and I've got 4 more to follow up! (It's an old model, so it gets carried on an empty chamber.)
Energy should be similar to a .44 Mag 180g (Federal loads a 180g Power Shock JHP to 1610, probably out of an 8" barrel). Penetration would be lesser, due to a much lower sectional density, but with a much broader "face", being a .50 ball. Interesting.
That is a mighty hot load you're throwing out of it. I assume the ball passed through? Any idea how the projectile held up?