I don't know how the muscle and bone tissue of large game differs from that of a human and the differences in power needed to drop either, but I can tell you that the Barret .50 is catastrophic to humans. Being in the military, I've seen videos come through e-mail showing various clips of Army snipers using the Barret to snipe Afghan snipers that were hiding in this hills around certain camps. Let me just say that "one shot, one kill" is an understatement with this rifle. Often times you can see large sections of the target's body flying off from the impact of the round (including arms and sometimes legs). It is brutally powerful.
As for accuracy, I'm an admin troop, so I can't claim to have ever shot one of these. However, I have a friend that is EOD (Bomb Squad) and they use the Barrets to "disable" IEDs from a safe distance. From what he says, it is fairly easy to shoot the detonation devices (blasting cap, electronic detonator, etc.) out of a bomb without setting it off from several hundred yards. So, take that as you will.