When the bolt has 45,000 CUP pressing against it it isn't going to move, you have the right idea about replacing the extractor spring. The two most used and abused springs are the extractor spring and firing pin spring.

Just replace both the firing pin spring and extractor spring, you should get faster lock times and less bolt jump. Sand, polish, stone the ends of the firing pin spring so they can't dig into the bolt body and the collar on the firing pin spring. The sharp ends cause torque to be stored in the spring when compressed.

Replacing the springs "might" very possibly help but your bolt and lug recesses just might be well polished from much use. Bolt jump to the best of my knowledge has NEVER killed anyone and it has the advantage of speeding up your cyclic rate of fire.

You must remember you have the slickest and fastest bolt action in the world and the Enfield action is slicker than snot on a door knob.

(replace the springs and see what happens, the worst that can happen is you will know your bolt inside and out)