Firearms use rapidly expanding gasses, typically from an explosive charge, such as smokeless powder, to accelerate a projectile down a barrel of the firearm toward a target. In contrast to bullets used in many rifles and handguns, shotgun shells include a collection of “shot” in the shell. The shotgun uses an explosive charge to accelerate a shot toward a target. Shot can take various forms, including various sizes, quantities, packing orientations, shapes (e.g., spherical, cubic, tetrahedron, etc.), and compositions. The shot may be initially contained by a wad during acceleration of the shot in the barrel. The wad exits the barrel of the shotgun with the shot while the shell remains in the shotgun. Conventional wads may travel a short distance with the shot, but are designed to experience atmospheric drag such that the shot separates from the wad in flight.
Shotguns utilize shot instead of a bullet to allow the shot to spread over an area as the shot travels from the barrel to the target. A bullet is intended to remain a single object during flight of the projectile to the target. The spread of the shot at the target may depend, at least partially, upon a number of characteristics of the shotgun and the shell fired, such as the muzzle velocity of the shot, the length of the barrel, the type of shot, and the distance to the target. The shape and dimensions of the area over which the shot spreads during the flight of the shot is known as the “pattern” of the shot. The pattern may be important to a shooter, as different patterns may be desirable for different purposes and different types of shot.
The shotgun itself may be altered or customized to modify the pattern of the shot. For example, the barrel may be shortened and/or widened (e.g., a home defense shotgun) to decrease the density of the shot pattern (i.e., create a larger spread to the pattern) at the expense of effective range and velocity of the shot. In contrast, a barrel may lengthened and/or constrained (e.g., a choke may be added) to increase the velocity of the shot and to increase the density of the shot pattern (i.e., reduce the area over which the shot spreads).
The wad may also affect the pattern. The wad will exit with the shot after moving through the barrel. The wad is lighter than the shot and will decelerate from drag with the air more readily than the shot, causing the shot and wad to decouple during flight to the target. Rotation of the wad during decoupling may cause the pattern to deviate in the direction of the rotation. Conventional wads are designed to decouple quickly from the shot to minimize the impact unintended rotation may have on the direction and, hence, pattern of the shot. However, after the shot is released from the wad, the shot may experience additional turbulence and drag in the air, causing the shot to slow and spread, reducing the effectiveness of the shot at distance.