I searched 30-06 loads in both of my old manuals Speer and Hornady. These books are both probably 30 years old right now or more. The Hornady had no loads listed with magnum primers only standard.

BUT the Speer manual was a different story. About half the loads in ever bullet weight list the possible use of magnum primers.

The important part of that information is to make it plausible that about any manufacture may have used either standard or magnum primers. Not that we KNOW they did or didn't just that it is plausible. ALLOWING for the possibility that one shell or a few shells of may be a different brand was mixed in with our characters bag of ammunition. MOST current bolt action rifles do not use removable box magazines. ONE OR TWO do. The newer current production Savage 110 something or other comes to mind but I don't think that is available in 30-06, only 223 which is a poor choice for multiple use applications including big or dangerous game.

The comment "bag of ammunition" is what sent me out that direction to explain why he is not using a detachable magazine. If our character used an M1 Garand he could be carrying a belt of magazine pouches with CLIPS of ammunition with 7 rounds in each.

Any way, meaning it could be plausible to have a hard primer combine with a rifle in the habit of giving light strikes any way, to give a dented primer that did not fire yet it does on the rest of the ammunition used in it.

This is going quite a long way in to the lands of "not likely" and the "never seen 'em" tribes. But it is the direction I'd look if someone brought that situation to me to help him figure out how to fix it.