OK..I have a Gen 3 model 23 and just purchased and Gen 4 Model 22. I upgraded my Guide and spring in the Gen 3 and Installed a Buffer. Has anyone upgrded their Gen 4? Also comparing the 2, aside from the Guide and Spring assemble, is a courios little bump on the trigger slide mechanism. Does anyone know why that was done?

Barrell 4150 Steel Preferred
Govt Profile
Chrome Lined Chamber and Bore
5.56 Nato Chamber
1/7 Twist
Parkerized under Front Site
M4 Feed Ramps
Magnetic Particle Tested
Stmped on Barrel " C MP 5.56 NATO 1/7"

Gas System "Mid Length"
Buffer "H" Style
Upper "A3"

Front Site Block should be "F" Marked
Make sure the Gas Key staking is Propper
Shrouded Firing...