Yeah, it was the XM177 I was referring to.

Back in the mid/late 70's I was at Ft Bragg, and did some training with some USAF zoomies that had 'em. IIRC, I was told that they unscrewed the flash hider, dropped a .223 bullet backwards into the muzzle and locked it in with the flash hider.
Never got to closely examine one to confirm that at the time, but I can say that they had no issue doing full auto mag dumps with blanks, with nothing on the end of the barrel.

I don't know about the cycling part but it's a training gadget that has been used as long as I can remember .

quote:

Originally posted by Haveme1or2:
I don't know about the cycling part but it's a training gadget that has been used as long as I can remember .

Since the early 1970s, or even a bit earlier. The BFA was adopted in the same time period as the birdcage flashider they were designed to mate with. The birdcage was initially adopted in 1967, and was installed on new production M16A1s and retrofitted onto older M16s by 1968/69.