I installed these new components in my old aluminum trigger assembly yesterday and had some problems. The gun would not fire in the binary position. When I finished the installation I had a leftover spring even though I followed the instructions. It was the new trigger return spring. I installed this trigger return spring and plunger and it still didn't work. The issue was the spring is too long and wouldn't allow the trigger to move far enough to the rear to allow the binary sear to engage. I cut about three coils off of the spring and it works like a champ. I suspect the newer polymer housings use a longer return spring and that is where the problem lies. This thing will dump a 25 round mag in what seems like 3 seconds. These are $299 online plus shipping so I went out to my LGS, Tick Licker in Corvallis and asked if they could order me one, expecting to pay a little more. The guy there smiled and pointed to a display rack on the wall and he had several for $295 out the door. Shop your LGS !