I've still got the stock recoil spring in my ported .40 and have no problem with it. I've considered going to a full length guide rod in it to experiment with the recoil and followup shots, but haven't gotten around to it. I can see a big advantage like, molonlabetn has said, if you compete and reload your own rounds. If you like the bunny fart rounds, you can have a light spring that would make them function unlike a stiff factory spring.