Re: 22LR conversion!!
Well, yes and no. I use one a great deal as a training rifle, but it's a dedicated unit, NOT the drop in kit for use on a 223 upper. I have one built by Derrick Martin (Accuracy Speaks, in AZ) and it is indeed a tack driver. Those units that replace the bolt and are used in a conventional AR upper are more like Minute Of Tin Can, at best. Several problems here that the Accuracy Speaks (and now several others as well) addressed related to the improper bore size (RF barrels are about .002" smaller than .22 cal CF barrels), a twist rate that twice as fast as it should be (1x16" vs the ARs 1x7" or thereabouts), the fact that the bullet travels about an inch and a half before it finds any rifling, and the fact that it has to pass over a gas port, which isn't helpful to the bullet or the upper's gas system. Lots of problems. Still, they're cheap, and can get you some enjoyable plinking time. If you're serious about accuracy, look at one of the dedicate uppers on the market these days.