Lone Wolf makes a AR-15 lower that takes Glock mags. Rock River makes a .40 S&W AR-15 upper. Use the Lone Wolf lower with the bolt and receiver from the RRA. All you need is to have a .357 Sig barrel made.
"No, it's not a silencer. This little doodad is my own invention. I call it a loudener." --Sledge Hammer