Abstract: A self-centering bore arbor device is disclosed which is self-aligning when inserted into the barrel of a shotgun and to which can be mounted a bore scope in a parallax relation with the central axis of the gun barrel. The self-centering property of this device is produced by a single source of pressure transmitted by a helical spring, inside a cylindrical bore collet tube, pressing against a circular 60 degree conical wedge inside the collet tube. This conical wedge distributes this pressure equally outward to the posterior free ends of three spring leaves displaced from each other about the posterior outer circumference of the collet tube by 120 degrees. Under this pressure the free ends of these spring leaves press outward against the inner wall of the gun barrel holding the collet tube in a proper concentric alignment with the gun barrel when the tapered muzzle plug forming the front end of the bore arbor is seated firmly against the inside of the gun barrel muzzle.

Abstract: A vehicle air horn is disclosed which is provided with heating cartridges and a temperature sensing switch. The temperature sensing switch automatically turns the heating cartridges on and off at predetermined temperatures. This automatic heating facility enables the horn to remain operational at low temperatures in inclement weather when other unheated horns would be expected to fail.