I was at the range a week ago. They only have a 25 yd range limited to handgun calibers. One person brought in what looked like an M4 carbine as I was leaving. A quick inquiry to him on this and he said it was convertible between 22 LR rimfire and .223 center fire. Later I saw a photo post from the Shot Show in Orlando that said Colt made something similar to what I saw. I'll be darned if I can find anything else on this. No info on the civilian Colt web site and I can't remember where I found the photos of the Shot Show. Can anyone help me out with this? I tried a forum search and came up empty. I realize, though, that this does not mean it's not there. Thanks in advance.