My neighbor (a fairly new reloader) was wondering if he could use small pistol Mag primers in place of standard small pistol primers he will be using these in several different calibers, such as 9mm, 40 S&W 357mag and 38 special. I didn't have an answer for him. I have been loading for a very long time and have never tried it and have never even used Mag primers in all my reloading years. I am sure they will be ok in the 357 mag where called for. As for the other three, there is a big question mark. Help me out here guys so I can forewarn him, if need be.