I have an extracting problem with my remington 700. once you chamber a round and fire it, it fails to extract it first go. I watched it trying to extract and it and the case gets about half way out of the chamber, then the case fires back into the chamber. on the second attempt, if you dont pull the bolt back in a hurry it will drop the round befor it has come far enough back to go out the ejection port.

Would cutting the plungers spring stop it from doing this?

with the rifle sitting on sand bags a foot or so above ground it will fire the fired case about a meter (about 1 yard)

It will help to some extent, but it sounds like you are do for a new extractor, it has lost some of its "spring" or was not shaped correctly before it was installed and is not getting full engagement with the shell rim. If it is the pop in type you can pop it out and reshape it, if it is the rivet type the process is a little more involved. I usually clip a couple coils at least off all the ejector springs.