There are some brands out there that are a little "ambiguous" about their standard vs. magnum status (Federal 205M's - I have a box labeled "Magnum" and a box labeled "Match", or Rem 7 1/2's are closer to a SR Mag primer than a standard), so I try to pay attention to that particular detail if I'm needing to change a standard primer, but other than that, a standard primer is a standard primer, a magnum primer is a magnum primer in my book. I wouldn't want to be at the very top end of my pressure tolerance with a lower pressure standard primer then feed it a "semi-magnum" standard primer and get into hot wax. So that's the easy one - stay safe...

Then there are some unique powders that aren't recommended for use with magnum primers either (2400), or some powders that are recommended for use with magnum primers and not standard (ball powder) so I suppose that's something to consider too.

Or there are low pressure loads out there that can get away with a thinner Rem 6 1/2 that might torch because they don't seal well with a rem 7 1/2 (harder cup), or loads that might flatten a soft 6 1/2 (204 Ruger).

After writing all of that - I have to admit - that's literally the most thought I have given to a simple primer swap, ever. Without the context of the cartridge you're loading to know if any of the above applies, or how close you are to the top end pressure, or what powder, then my mind goes to all of those considerations.

But if I think about my 223rem pet load that I've been shooting for the last 7-8yrs - and we all know how crazy it has been getting primers during parts of that time - I've substituted CCI 400's, 450's, 41's, BR4's, Federal 205M's, Rem 7 1/2's, and WSR's without changing my zero or my charge. A near-max load of Varget that's very well behaved. While not quite as many different primers, I've done the same with IMR 4064 in the 30-06 and H4198 in 45-70 - any primer that fits is fine.

I tend to load always with the same primer, just for consistency, but I've had enough instances where I've needed to cross-pollinate that I've tried it out, with almost NO noticeable effect, that I can't say that I believe there's a big difference in primers.

I used to think I was being a bad reloader, or being irresponsible when I did that, but I read a bit about the Houston Warehouse a few years ago and after hearing their results, I pretty well decided that the differences in primers only matter to my firing pin and striker or hammer spring - not to my load. Very interesting reading, if you ever have the time.