Re: Mag primers in non-mag cartridges?
Other than cold weather performance, or a substantial quantity of hard to ignite ball powder, there is not much reason to use a mag primer, except for the thrill involved?
I think mag primers, in hot varmint cartridges are not recommended. If you accept the theory that capacity versus bore size will indicate a slow burning rate powder, then the mag primer defeats the purpose, and accelerates your burning rate, yielding slower velocity than a controlled burn with a large rifle primer.
In my 300Winchester, for example, I have always used W8½ primers and 80 grains of H4831, which produces a relatively hot spark (165) I could be wrong(?) but I think that Winchester uses that exact primer in loaded 300 Win Mag ammunition. And, yes, it is a hot large rifle primer. That tells me that Mag primers have a very narrow application. In other words, not a blanket solution. Unless you have a definite purpose, and understand the cause and effect.
Good hunting. LB