Had a friend give me a few hundred of these. From what I understand, magnum primers are harder rather than more powerful. Can I just substitute these or do I need to work up a load again. Not looking for any accuracy, just plinking. .223 current load is a Rem BR primer (#7 1/2 I think), 24gns of H335 under a 55gn FMJ which is nowhere near max and shows no signs of pressure.