Be sure your chamber doesn't have an invisible build-up of plastic from some shells.
Also, I'd give the entire bbl. a good scrubbing for the same reason. If that checks out I'm sure that it could be dirt of some kind fouling you up. I'd remove the trigger group and use some Gun Scrubber - but I really think it could be plastic build-up in the chambers.
If not putting new extractor springs shouldn't be a problem if you watch what you're doing.