I have seen them and thought about getting some. I have read though that they may have functioning issues in some pumps or autos. If they feed and eject ok they would be great for HD loads as the magazine would hold quite a few.
I have some and have shot them. They will not function in most pumps, and none of the autos. Some claim limited sucess in Winchester 1300 pumps. They were designed for the Poseidon(sp) pump. I remember seeing an article in GA a few years back about it. I believe it would hold 10 or 12 of the little shells. Flopped. Now they are dumping the ammo. My dealer has quite a bit of it and it is decent for kids shooting 12 gauges. Recoil is less than full house, but more than you would think from looking at the shell. But like I said earlier, it will not function in pumps from my experience.