I found factory supplied steel nipples burnt out in less than 10 shots in my .45/.44 rifles which shot long cylindrical slugs and heavy loads ,PH Whitworth , Henry, Rigby , and Pedersoli Gibbs , the first 3 shots would be dead on then the shots would start to drop as the hole burnt out letting the pressure / velocity drop .Hard stainless nipples were good for 50 or so shots , Beryllium nipples were much longer lasting and I never wore ( burnt) out a platinum lined nipple . Shooting patched round balls , beryllium nipples seemed to last indefinitely .