Originally Posted by Any Cal.
There is a test for the recoil spring... With the chamber empty, pull the trigger and hold it. Raise the muzzle to vertical and pull the slide back then let go. The slide will want to move forward, but will be unable. Slowly lower the muzzle toward horizontal, the slide should return to battery by the time you get to 45* elevation. If you have to go nearly horizontal, the spring is too weak.
You might also check for crud under the extractor, or gummed up extractor.
Wow! I had 2 FTF's yesterday at my local indoor range and today I read this post. Sure enough my G20 did not pass the test. I don't think I've shot more than 2,000 rounds on the original factory spring but maybe I have...?
I ordered a stainless guide rod and complete flat spring kit from GlockMeister. I anticipate running the 20lb spring. I mostly shoot Underwood, Double Tap, Remington, Georgia Arms ammo.-( More Remington and Georgia Arms target ammo than the other two ) Thanks for the info.! Also, I had an FTF with 200 grain hardcast this past summer and subsequently swapped out ammo for Underwood 200 grain XTP's which cycled just fine at the time. My recoil spring may have needed changing for as long as a year. Again thanks for the info.