Originally Posted by alaska
Thanks for all the replies, I was just looking at the MK 248 Mod 1 load and noticed they use a Fed 210 Match with a very heavy dose of H1000 with the 220 MK. I bet it's just to keep the pressure down a tad.
I normally use magnum primers in Magnum rifles, but since this is such a heavy load......I don't think I will duplicate it at that levels.
With such a slow powder and with the amount of powder being used I highly doubt a Magnum primer will add any significant pressure to the load, especially if you don't load the bullet right up against the lands. It will however insure a complete and clean burn so I would use a Magnum primers in loads of that type.
If I read that load correctly it's 75.7gr H1000 and Hodgdon lists a Max charge of H1000 under a 220gr bullet @78.0gr with a Win LRM primer. According to that data you can safely use a magnum primer. (I would)