So many newcomers to the reloading scene tend to think that if their cartridge is labeled "Magnum" then so should their primer, and vice versa.
The word "magnum" is a marketing tool and it really has been since it debuted with the .357 Magnum. Well, debuted in our corner of the world. Before the first Registered Magnums, "magnum" was a large bottle of champagne, and little else as far as I know.
The term ends up being one of those annoyances that are not held to a standard. Perhaps the finest example is the .32 H&R Magnum which, by any rational line of thinking should have most definitely been named the .32 H&R Special and nothing more. Look at the muzzle velocities and SAAMI max pressure of the cartridge for all the evidence you might need.
When the first "magnum" primers were debuted (I have no idea), it would have been quite nice of them if they'd found a different name for them. I consider this one of those annoyances that complicate things for those new to this hobby -- not at all unlike the Hodgdon "Clays" series of powders where we have "Clays", "International Clays" and "Universal Clays." More and more we see them being simply called "International" and "Universal" but jeez, something this important should never
be made easily confused.
My next annoyance which I will not address:
Boutique ammunition producers that label and market "+P" products in any chambering that isn't .38 Special, 9mm and .45 Auto, with an exception for .38 Super. (another annoyance)
I need to get some coffee.