40 grn winchester hp's, and you'll have passthrough's on broadside body shots.
Don't try to recover/follow up for 30-60 minutes. Although he's shooting them with a rifle, follow up should be similar to bowhunting. 60 yards give or take, or into the closest cover, and they lay down.
I'd be more in favor of a head shot than high neck if it were me. If the kid can head shoot a squirrel, then a head shot on a deer is viable.
