I just did a complete MCARBO job on the PF9 I’ve carried for 11 years. Prior to upgrades, it was 100% reliable, if a bit uncomfortable to shoot. Now it feels great, has a great trigger, and fails to fire about every other round due to light strikes. Seems like the MCARBO hammer spring is a little weak, or else the MCARBO recoil spring isn’t quite getting the slide back to full battery—not sure which yet. Anyone else have this happen? I’m thinking I should go back to the KT spring and keep the MCARBO trigger. I’d appreciate hearing experiences. Until I get this ironed out, I’ll go back to a .38 snubbie.
Check the firing pin spring, possibly is interfering with the firing pins motion. Use a punch and feel if the firing pin moves without drag and only a spring force. I’ve shot their kit without an issue. Also assuming you are using new manufactured ammo.