Magnum Primers

Magnum primers contain a greater amount and/or slightly different explosive mix than is used in standard primers.  On ignition, magnum primers give longer burning, hotter flames.  Their use is recommended for (1) any ammunition that will be used at or below zero degrees F., (2) with most Ball powders and (3) with slow burning rifle powders like MRP and IMR 4831 in very large cases.  Magnum pistol primers often will give more uniform velocities in magnum handgun cartridges loaded with large charges or slow powders like 296, 2400 and H-110. Magnum primers may be used with faster burning or easy-to-ignite powders, but normally there will be no advantage in doing so.  As when changing other components, it is advisable to reduce powder charge weights on initial loading with magnum primers.