Don't know what your budget is, but you may want to try a Ceiner or other conversion along with a dedicated upper for your .22 rimfire needs. I was checking in to this and Derek Martin, the owner of Accuracy Speaks builds one with Douglas or Kreiger barrels with a twist rate more conducive for accuracy with the rimfire cartridge.
http://www.accuracyspeaks.com
You may want to email him for a snail mail catalog and a price quote.