Image Number 6 for United States Patent #5970878.
The combination of a shot sleeve and a shot cup base form a universal shot wad that precisely fixes an adjustable volume for the shot column of a wide range of shot shell loads. The shot sleeve is a generally tubular member with an open end and a closed end. The inside of the shot sleeve is substantially smooth adjacent to both the open end and the closed end and has a plurality of substantially parallel, inwardly projecting, first ribs circumscribing the inside between the smooth portions.The shot cup base is a second tubular member and also has an open end and a closed end. A plurality of substantially parallel, outwardly protruding, second ribs circumscribe an outside of the shot cup base. The volume of a shot receiving portion is controlled by inserting the shot cup base a desired distance into the shot sleeve such that the two sets of ribs interengage. Apertures formed through the shot cup base cause the sidewall portions of the shot cup base to segment and open outward on expulsion from the muzzle of a shotgun increasing aerodynamic resistance. The increased aerodynamic resistance causes the shot cup base to separate from the shot string minimizing interference of the shot flight pattern by the shot cup base.