Do a Google search on "Savage Axis Trigger Job" and you will get a couple of hits for this site. Check through them and you will get more information. I think the screw size was 10-24 and about a half inch long.
I just saw that somebody is selling an aftermarket spring on Amazon for $15 that will do the same thing. It just uses a thinner wire and still coils it to fit the screw hole like the factory spring.