Originally Posted by
tirod
I thought that at one time. What moves the bolt carrier on a .22 blow back, or the slide on a semi auto pistol? Gas pressure in the case pushing back against the bolt face.
Roller locked bolts on HK's? Case forcing the bolt back. There's no operating rod.
I believe DI just opens the bolt. Case pressure pushes the bolt back, rotating the cam pin and forcing the head against the upper track, where the TM states to "lube generously."
If I had two AR's, I could demonstrate by connecting the gas tube of one to the other, observing whether it would cycle the bolt on the non fired gun, extracting, cocking, ejecting, and reloading. That would eliminate the affect of gas in the barrel.
I don't even think it would eject.