Bronze Spiral Threaded Barrel. The MR920 is a feature-packed, compact-sized pistol that is designed to work with existing Glock 19 holsters, magazines, and gear. The match-grade barrel is conventionally rifled and spiral-fluted to improve evacuation of debris. MR920s are also available with threaded barrels. The drop-safe, flat-faced aluminum trigger has a 4.5-5.0 lbs trigger pull and a crisp, tactile reset. Optic cut models allow shooters to mount the mini red dot optic of their choosing. This pistol comes with a factory mounted Holosun 507C.