A choke tube assembly having a rear part and a front part selected from a plurality of front parts is releasably retained within a stepped cylindrical bore in the muzzle end of a shotgun barrel. The front and rear parts cooperate to define a forwardly converging forcing cone contiguous to a cylindrical choke bore which opens through the forward end of the front part. Each of the front parts define a choke bore of a different diameter. The shot pattern characteristics of the gun barrel may be altered by substituting one front part for another having a different choke characteristic.

A shotgun barrel assembly for producing a prematurely enlarged shot pattern has an axially position on barrel and a barrel extension mounted in fixed position on the forward end of the barrel. The barrel defines a shell chamber and a bore which communicates with and extends forwardly of the shell chamber and opens through the forward end of the barrel. A portion of the bore forward of the shell chamber is generally cylindrical and terminates at a conically tapered forwardly diverging portion which opens through the forward end of the barrel and has an axial length at least equal to eight times the diameter of the cylindrical portion. The barrel extension defines an expansion portion which forms an extension of the bore and which has a diameter greater than the major diameter of the conically tapered portion. Compensating slots may be formed in the barrel extension portion.