Given the tremendous diff in recoil between 308 and .22lr, and the range limitation of the .22, and the stiff price, I really have my doubts about the return on this investment. $150 on a Ciener .22 unit for the AR, ok, but better yet, $100 for used one, proven reliable and accurate, with a 30 rd mag. :-) then you can't lose, and since the 223 has about half as much recoil as the 308, and almost all of it is gone if you add a suppressor to the AR, now the 22 unit practice truly will result in 223 ability, especially if an optical sight is used.