US Patent 7895787 Porting feature for firearm

A choke for use with a shotgun is provided. In accordance with one embodiment the choke has a body that defines a bore with a longitudinal axis therethrough. The body is configured for engagement with a shotgun, and the bore is positioned for traversal of a wad and shot therethrough and out of an end of the bore. The body has a circumference, an inner surface, and outer surface. The body defines at least one port for venting gas from the bore that extends from the inner surface to the outer surface. The shape of the port at the inner surface is asymmetrical.