[Unclenick]

If you have or know somebody with a headspace measuring tool for brass (RCBS Precision Mic, Hornady (formerly Stoney Point) case gauge, etc.), check one of your once-fired cases against the new brass. As suggested, it will probably turn out to be more than just the normal 4-10 thousandths longer. This means the cartridge is so loose in the chamber it is being thrown farther forward than the firing pin can quite reach. This situation can be corrected, or you can use some more sensitive primers, like Federal, to get the cases to fireform, then set your sizing die up not to push the shoulder back all the way, but just enough to chamber easily. The cases are then married to that one gun.

The other thing I would do is a complete disassembly and detail cleaning of the bolt. My K38 Swede came so heavily packed in grease I was amazed it functioned at all.