GLOCK GEN 4 20-21-40-41 & SF Models
DPM MECHANICAL RECOIL REDUCTION SYSTEM
This system works due to the multi spring intricate rod (three springs) and controls the functionality of the pistol. The third spring which is contained within the rod controls the movement of the slide so it never rams on the frame.
The system includes two different in length washers and two external springs. Washers differentiate only the buffer force (slide full open position) and the external springs differentiate only the slide closed position (slide on the battery). The shorter washer offers a light buffer effect and the longest washer offers the heaviest buffer effect.
The external springs are different in length with the longer offering heavier slide travel and locking than the shorter spring.
Caution: Always use ONLY One washer.