The 500 S&W is a handgun round, so finding rifle ballistics will be damn near impossible. Even trying to "massage" specs for comparable rifle rounds is tough. You got a lot of lead and not much powder, maybe just modify the handgun ballistics. Velocities, trajectories, and energy, etc. are probably lower specs with the 20" barrel than the 10"handgun. Would be interesting to see.

I bet you're looking at the T/C Encore in 500S&W, huh? Maybe their support could help.