The powder manufacturers make specific recommendations about which primer to use. Magnum primers are only recommended for heavy loads of slow burning ball powders. You won't get in trouble following Hornadys load recommendations because they pressure test their loads before publishing them, as do almost all component manufacturers. There are some companies that only manufacture tool & accessories, and personally, I usually avoid their data, but there are some notable exceptions to this personal rule, such as Lyman & RCBS, who often list the pressure data for their loadings.