I would want something, where the bullet will open up quickly and turn his switch off fast. If its just for leopard, a .308 Win, 30-06, 7/57, with thin jacketed bullets quick expanding bullets. It wants to be a tack driver and sighted in dead on at what ever your PH suggested range is, with a low power scope good light gathering scope. I have a 20" barrel L57 Sako/manlicher .308 Win that Im just dying to use on a Leopard, it will shoot cloverleafs at 100 yards.
Bob