Re: Magnum or standard primers
I have used Remington 9.5M primers in loads developed for several .22-250's, .243's and a .25-06. I always started at the bottom of the powder range and worked up looking for pressure signs.
Some of the loads developed in the .22-250 and .243 were using H414 powder. Now I'm not saying a magnum primer is needed with this powder, but I was doing load development (read as: experimenting) and did find accurate, repeatable loads. YMMV. JohnnyK.