It would look hella cool! There was a carbon fiber ar out a while back and they make jets out of the stuff so it must be ok. I'll bet you could mock up the gun and maybe even test fire it before glueing it all together (or what ever fancy name they call it). If you're doing a dedicated 22 you don't have to worry too much about the buffer tube diameters or length as the 22lr versions use their own recoil system. That would open up a whole bunch of custom stock options for you. Maybe you could even make a galil type folding stock for it. If you're doing your own barrel how about one of the alumilite 22lr barrels for the 10/22? Its basically an aluminum barrel with a steel liner. They also make a tenion (ms?) barrel thats aluminum on the outside and has an air space around the liner on the inside. I don't think that would work well to remachine into an ar15/22 barrel. One of my back burner projects is a 17hmr upper for an ar15 and I'll be using a 10/17 mag barrel for it. I have the bolt done except for an extractor. I just need to make a bushing for the 17hmr bull barrel so I can bolt it onto the upper. I've been toying with a delayed blowback idea for it also.