New RUGER 22/45 Threaded Barrel Rimfire Ruger® 22/45™ Threaded Barrel Rimfire Pistol Models Introducing two new 22/45™ rimfire pistol models with threaded barrels. These new models allow owners to attach an assortment of muzzle accessories to one of America’s favorite rimfire handguns, the popular Ruger 22/45RP rimfire pistol. Both models feature a 4.5 inch, factory ½-28 thread barrel, which accepts many popular muzzle accessories. When not using a special application attachment, the threaded barrel and barrel crown are protected by a muzzle cap. The 22/45PRRP model (10149) comes without sights and features a Picatinny rail on top of the receiver for mounting optics. A shorter Picatinny rail is mounted on the bottom of the barrel for attaching lights, lasers and other accessories. The second model (10150) features a fixed rear sight and Partridge-style front sight. The receiver is drilled and tapped to accept a Weaver-style scope adapter (available at ShopRuger.com) so shooters can mount a variety of optics on the pistol.