Well, heard from Ruger this morning. I can at least use a hi-viz front with the stock rear sight. The reason ya can't use the adjustable is that the bbl is so short you could never get the rear sight low enough o get the proper sight picture. As a side note my gun was missing the key for the internal (infernal) lock and they are sending one no charge.. Have yet to get bad service from them. Folks wonder why most of my guns are Rugers....