I found out that the 209 was a shotshell primer while the 210 is a large rifle primer.

Can Large Rifle magnum primers be used in place of large rifle primers?

Natches has Large rifle magnum primers!

Greg

Yes you can. If you have max loads (actually I'd do it anyway even if not max) developed with LR primers, reduce it and work it back up with the magnum primer.

M1G,
Thanks,
Greg

Essentially, the magnums ignite a bit more of the powder than do the stds. This gets more burning sooner. So, the charge acts as if it were a faster powder. The general trend is that a smaller charge of a faster powder is required to maintain the same peak pressure. That's why one has to do as M1Garand said above.

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