Abstract: An elongated base is provided for mounting on a gun barrel with the base extending longitudinally of the barrel. The base includes opposite end portions and a longitudinally slotted mid-portion extending therebetween. A pair of scope mounting rings are seatable against the base on one side thereof through which the slot opens and include outstanding mounting lug portions projecting into and slidable along the slot of the base. The mounting lug portions include aligned bores extending therethrough longitudinally of the slot and an elongated shaft is disposed in the slot and extends through the bores. An abutment member opposes the opposite side of the body through which the slot also opens and includes an anchor lug projecting into the slot between the lug portions.