CGW 3 Spring Kit! (Hammer Spring, Firing Pin Spring and Firing Pin Block Spring). Get the hardened firing pin retaining pin while you are at it. Keep the recoil spring stock unless brass is trickling out or flying out to the next county.
I've used their 3 spring kit on my PCR and one for a Full Size with the stock firing pin and shot a variety of ammo all of which goes bang and dents the primer nicely. Some will recommend going with extended firing pin for 'guaranteed' primer ignition. Shoot it until you are confident everything is working fine.