It works even better when you install the whole kit.I installed the PRP striker spring today and it made a big difference in the trigger pull. Do I or should I change all the other springs as well? I can't see where it would make any difference.
In the post-recall world, the grip safety spring has been shown to add to the trigger pull weight so you would expect that you could see some change from replacing it (and in my case, there was - to the tune of about 10-12 oz.) The others? I'm not really sure what effect they could have - probably mostly to make you feel like you got your money's worth from the kit.In the "pre-recall" PRP trigger spring kit, all of the springs were installed EXCEPT for the striker spring in my XDs. They yielded 1 ounce of trigger pull reduction as measured on a Lyman digital gauge. Worth the effort? Not.
The others? I'm not really sure what effect they could have - probably mostly to make you feel like you got your money's worth from the kit.