Jona, I was reading a debate about a problem like this on SurplusRifle and they seemed to think that the ejector screw in the receiver is a vestigial hold over from the mkIII that doesn't eject the rimless cartridge. There is a bit of the screw protruding, but I don't have anything to compare it to. They seemed to think problems like this are from the lip on the mag not grabbing the cartridge. The spring in the mag also doesn't seem very tight to me. Could that do it?

The extractor spring is in the bolt, correct? I remove the little screw on the side of the bolt-head and pull the extractor out of the bolt, right? I'll check that next. Is there anything really tell-tale in there to look for? I mean, would the spring be physically compressed or broken, or would it just be that it isn't..responding? Springing? I don't know how to put that, but maybe some oil wouldn't hurt, eh?