According to all the "stats" that have been written, I'll have to agree with Jack Roberts on Win748 and WSR primers. As usual there is always the exception for individual weapons. However reloaders need to consider all the components, both cartridge components and weapon components. Such as; primer, case, powder and bullet brand and style. Same for the weapon; auto, lever, bolt, etc., barrel length and twist rate. Lots of variations, Lots of varied results. Only a rule of thumb, but, usually medium to fast burn powders do not require a mag. primer. However ball powders are treated a little different. But, as Jack Roberts stated, "Win primers are a little hotter". I only can imagine that the previous statements are really going to cause a stir.