It doesn't sound like the ammo is the problem, but of course that can always be a possibility if you are talking about 50 year old surplus.
In addition to having some cosmoline stuck in there, as was said, I know with a Mosin Nagant, if you don't get the right amount of rotations as you put the bolt back together you can get light primer strikes because not enough of the firing pin is protruding from the bolt face.
I've not had that happen with my Mausers but I suspect you could have the same thing happen.