Back in the late 90’s, subsonic 5.56/223 ammo that would reliably cycle an unmodified M-16 or AR-15 was only a mythical beast, at least in the circles that I ran in. I understood the premise that a heavy-for-caliber bullet was needed but nothing off the shelf was readily available.
The heaviest projectile I had at the time that would stabilize at subsonic velocities was a Speer 70 grain semi-spitzer. While I had developed a 5.56 load that was accurate and displayed consistent shot to shot velocities, it wouldn’t even budge the bolt of an M-16 rifle. So I applied a little redneck-tech and soldered together two of the 70 grain projectiles, base to base, ran them through a .224 size die, and made my own 140 grain bullet. Not only was the projectile really ugly but it was slightly banana shape. After some trial and error using numerous powders I came up with a load that gave fairly consistent velocities of 1,000-ish feet per second. With some small degree of confidence I loaded a magazine full of my new creation, put a suppressor on an M-16 with a 14 1/2” barrel and a 1-in-7 twist, fired a few rounds semi-auto then went full-auto into a thin metal plate at 25 yards. Every bullet went sideways through the plate but the gun cycled flawlessly and even locked the bolt back on the last round. I was half way there.
Eventually I found a couple bullet manufacturers who made 100 grain jacketed lead core projectiles for me, at a cost of fifty cents a piece, that worked quite well. I spent several years running around the country demonstrating the ammo to numerous state and federal agencies but it was never considered anything more than a novelty at the time. It was during that time we recorded this demonstration video.
On a side note: a friend of mine who manufacturers suppressor gave me a can that he had just completed with a new baffle design for this demo. He failed to clean all the cutting fluid out of the can during assembly so when I fired the gun during the demonstration the suppressor spewed large volumes of smoke….go figure.