Patent ID: 7810480

Claim:
An accessory for coupling to a modular lower receiver of a rifle to form a crossbow, the modular lower receiver having a housing, a trigger extending from the housing, and a hammer operated by the trigger, the accessory comprising in combination: a. a riser having a central portion and opposing end portions; b. first and second limbs coupled to the opposing end portions of the riser, the first limb extending from the riser toward a first limb tip, and the second limb extending from the riser toward a second limb tip; c. a bowstring extending between the first limb tip and the second limb tip for propelling an arrow; d. an elongated frame member having first and second opposing ends, the first end being coupled to the riser, and the second end being adapted for coupling with the modular lower receiver; e. a string retractor coupled to the second end of the elongated frame member for pulling the bowstring away from the riser toward a drawn position proximate the second end of the elongated frame member; and f. a bowstring release capable of being disposed proximate the modular lower receiver, and being responsive to the hammer of the modular lower receiver for selectively releasing the bowstring when a user pulls the trigger of the modular lower receiver.