03-22-2011, 04:37 PM
Well, the harder cups can take more pressure, but I don't know if that is an issue with the grendel. 5.56 is loaded to pretty high pressures. It is probably just the product of some very experienced reloaders that don't use anything but magnum primers because they believe that they improve the standard deviation. Thats just a guess. I don't use magnum primers.
