Re: 22lr lower-223 upper?
I have a 22LR, but it was built form the ground up as a rimfire training rifle. Completely identical to my 5.56mm NM Service Rifles, which was the whole idea. The lower, however, is a standard AR-15 pattern lower, and could be converted to centerfire simply by swapping the uppers. I've never messed with the various 22 "ARs" that have popped up recently, beyond handling them in the stores. Didn't like the feel of them, since they were obviously built to be more plinkers (in my opinion, anyway) than serious training rifles. Didn't get the impression that you'd be able to convert these to take a standard upper, or use centerfire stuff in any way. I love my 22LR, and use it extensively, but can't get too excited about the dedicated rimfire versions that are out now. Big difference between them and the CLE's, Accuracy Speaks (the one I have) and the CMMG versions that all use standard AR components .