" a striking problem, but only when the barrel is pointed down"



In this picture below, the rounded tip of the firing pin looks broken off. Like Floyd pointed out it looks like a Flat nose. I wouldn't be surprised to see the slotted area of the Firing pin is wobbled out where it intersects with the stem of the Extractor... Allowing the Firing pin longer travel. Have seen this before.

If you enlarge the OP's last picture of the bolt face... You can also see under the Plunger cone that the extra webbing (below the left side of the Extractor) has a rough/burred area. To me the Primers have a larger diameter impact area, not like a U imprint the spent casings in my hand look like. Maybe this 'Blunt Impact' is in part the reason the Primers are backed out?

If mine, I would swap out the Firing Pin, File away the rough edge on the bolt Web, install a new Extractor, Plunger Spring assembly, and install a new Ejector spring. If the Ejector tip is in good shape and working properly it could stay. But for a few $$ more you could have a rebuilt bolt and change the Ejector tip/spring assembly. Anything still in serviceable condition become extra parts.

I'd be interested in seeing a Macro pic of the current Firing Pin tip.



Pic from a Auction showing Firing Pin Tips: