Granted the primers could come apart from the back pressure. And I could lie and say this is one reason I seldom shoot large charges of powder out of plunger guns. But I shoot smaller charges for accuracy reasons only. If a magnum charge brought me accuracy, believe me.. I would be shooting them. But in all honesty.. I have shot stout loads out of the Black Diamond XR (150 grains of loose powder) and the primers stayed in tact.