Thanks for the input guys.
I don't think it's a firing pin problem, because the action doesn't open far enough for the lower edges of the chambers to catch on the firing pins.
Further investigation, however, has revealed a broken ejector screw. I'm not sure what effect this has, though, as the ejector seems to be staying in place. I guess that's the first thing to be replaced...though I may need a whole new ejector, since the screw is broken off in it. I'll keep you posted.
Dumb question #453...the extractor appears to be just that...not an ejector. When I get this screw replaced, will that turn the extractor into an ejector? If so (Dumb question #454), can I make it not be an ejector? I intended to use this for CAS which, of course, doesn't allow ejectors, and will defeat one of the major reasons for this whole project.