Spikes Tactical .22 LR Convertion Kit for the AR-15

Over 6 months ago I purchased this convertion kit for my S&W M&P 15. The original kit came complete with the bolt, addition recoil spring, gas block with pin and one magazine. I purchased and additional magazine and was grateful. The cost was $199.99 for the original kit.

The instructions stated that you may have to cut the recoil spring and test fire until you reach an optimal performance level. ie not miss fires FTF or jams FTE

I found the main difficulty was FTE's caused the FTF's. The recoil spring was so tight that the bolt would bearly clear the next cartridge. This caused the bolt to fail to deliver enough momentium to push the next cartridge into the camber.

The manufacture states that to correctly tune the spring you must cut 3 coils off at a time and then test fire.

I found that I had to cut 1-1/8" inch off the spring. After that modification FTE's rarely happen.