I am putting together a Not-So-Dedicated upper. My Gunsmith talked me into building a cheap upper that is still chambered 2.23 5.56. This way I have a something that will shoot .22lr, but could still be a real rifle at the end of the day (or if something breaks). I have all the parts less the BCG.
I bought the CMMG .22lr conversion from Mike at Bowers Tactical in DTC (big thumbs up). When I get it back from the smithy I will post my experience and hopefully some pics and range report.
The only drawback so far has been trying to find reasonably priced AR parts lately. A lot of phone calls and driving.
Pedro