I can probably use the magnum primers in the Garand since there is a possibility of slam fires with regular primers.
You can use the WLR magnums in the M1 with no problems. The Milspec CCI-34 primers which are made for M1s, M1As and other autoloaders are actually magnum primers. Slamfires aren't an issue with Winchester primers, or most any other primers so long as you seat them below flush.