BEAMSHOT RF2/B - Laser Sight Mount for round barrel firearms All 20 gauge shotgun .223, 250, 257, 270, 7mm, .30 carbine, 308, 30.06, 300, 375, 416 cal. rifle / autoloaders. Revolver S&W model 14, 17, 19, 27, 29, 57, 586, 686, 657, 6" barrel; revolver Ruger red hawk, super red hawk, black hawk, super black hawk, 7.5", All 16-20mm(.63"-.79")OD round barrel.