Regarding Rifleman1776's post:
Loading tens of thousands of rounds with "no problems" is not informative at all. You did not bother to specify that even one of those rounds was loaded with a powder for which the manufacturers or manual developers recommend a magnum primer.
And, a letter that you "still have" of unspecified date with a similar opinion from "the NRA Dope Bag" provides little more credibility in this day. Dope Bag has been around far longer than some of the modern ball powders like H-110 for which magnum primers are specified. Primer manufacturers even revised their primer mixtures to accomodate some of those powders, years ago.
I think it is far wiser to take the advice of the people who run their load developments with substantial test instrumentation like pressure transducers and chronographs. They should know best what a powder needs to ignite and burn properly, as well as what can produce excessive pressures.