Re: Mag primers in non-mag cartridges?
Absolute best accuracy I can get in my 223 match rounds is with mag small rifle primers. I don't use ball powder.
I work all my loads up from the bottom in all cartridges so pressure is not a concern. IE I won't swap a regular to a mag without backing down and starting over.
I have seen higher MV with match primers than with mag primers.
IMHO you cannot learn much from the label of primers(IE how hot per mag, reg or match etc....) And you simply have to use what works best. I've been able to double or triple group sizes with same powder by swapping primers. I've also cut group sizes in half or less by same tactic.
I test with every primer made at times. Just to see. I have loaded too long to get hung up to have to use a mag primer only in mags etc...
Get as close as you can, but utilize your skills as needed.