A device and method of using the device to attach an accessory to a firearm. The device is a longitudinally elongated, rigid, two-piece clamping coupling forming a longitudinally extending channel with a longitudinally extending seam and a longitudinally extending lateral gap in the coupling between the pieces. A set of longitudinally spaced clamping screws operably engaging both pieces of the coupling and extending laterally across the seam for laterally repositioning the pieces relative to one another to effect compressive clamping when rotated. A longitudinally extending receiving track is formed in at least one of the pieces.