I had one of the knives ironhead described above. Bought it out of Shotgun News back in '85 for about $100 if I remember right. The sold them unrestricted, or at least at first they did.
Overall, it was fairly well made, except for the "trigger". Mostly it was aluminum, with a steel bayonet type blade. You could fire it with or without the baton cover. It did use a very heavy spring, and it was a bear to "load", and once loaded, it was a scary thing to have in your hand, as the "trigger" was easily bumped off, if the grenade pin safety was not in place.
Mine would stick into sheet rock at 10', but would barely stick in a sheet of plywood, or any wood, at the same distance. It was "supposed" to kill at 30+ feet, and I suppose maybe it could, in the unlikely event all the stars and planets just happened to be aligned precisely, and it were to hit something vital at that distance. Still, I wouldnt want to be on the receiving end of it. It was actually pretty cool, and I wish now I hadnt traded it off.