Mesa Tactical, Remington 870 Magazine Clamp, Rail & Sling Swivel

The magazine clamp can be used to more securely retain aftermarket or factory magazine extensions, while at the same time offering flexible accessory mounting options near the shotgun muzzle. All Magazine clamps are available with a push-button quick release sling swivel or a two inch MIL-STD-1913 (NATO STANAG 4694) Picatinny rail that can accept standard weapon light mounts. The Magazine Clamp can also be used to mount one inch diameter weapon lights simply by clamping one side to the shotgun barrel and the other side to the light body (recommended for use with shotguns with tall front sight posts). 

So far, Mesa Tactical clamps for the Remington 870 and Mossberg 930 shotguns only (they happen to have the same dimensions). Demand for additional platform support has been resisted because of the difficulty in supporting the wide variety of, for example, barrel diameters and other differences between shotguns within the same model series.