If your pistol is a Gen4 you need the new issue Gen4 recoil spring seen here http://bit.ly/qlO0AM
or one of our Gen4 recoil spring adapters http://bit.ly/iYhdYq
and an 11 lb recoil spring. Here is some more info you will find interesting:
About 1% of our 9mm conversion barrels are affected by the poor performance of low powered 115 grain ammunition causing a Failure To Eject (FTE). A good example of ammunition that is “most likely to fail” is Winchester White Box (WWB). This rare failure is too low a percentage to make an issue, however it is one we are well aware of. The fix to resolve this issue is quite simple:
1 Clean and lube your slide and barrel.
2 Shoot 1 mag to 1 box of good quality +P or +P+ ammunition through the barrel.
3 Try the FTF ammunition again. If it runs... great! If you experience more failures you will have a couple choices to make:
Fix A Reduce the recoil spring weight to 11 lbs. Cost is about $25 for stainless steel guide rod and reduced power spring.
Fix B Shoot 124 gr or a better quality 115 gr ammunition exclusively. The FTF 115 gr ammunition you are currently using is no longer a valid option.
What causes this problem? Several issues come into play.
1 The 40 slide and (40 conversion) barrel is thicker than any standard 9mm slide and barrel. This extra thickness equates to more weight. The combined extra weight taps the energy of the "weak 115 gr ammunition” to its complete demise. It simply lacks in power and fails to reliably eject the spent round.
2 Every once in awhile a Failure To Feed/Failure To Eject (FTF/FTE) is caused by a fit issue. We resolve fit issues by pumping +P or +P+ ammunition through the gun. This hot ammunition provides extra pressure and the pressure will positively align any and all components. Once they are all aligned there is no longer a fit issue. The FTF/FTE is usually resolved.
FYI: Several manufactures are currently producing low powered 115 gr 9mm loads. This ammunition is also known to produce failures in all standard model Glock 9mm pistols.