<P> In firearms, a choke is a tapered constriction of a shotgun barrel's bore at the muzzle end . Chokes are almost always used with modern hunting and target shotguns, to improve performance . Its purpose is to shape the spread of the shot to gain better range and accuracy . Chokes are implemented as either screw - in chokes, selected for particular applications, or as fixed, permanent chokes, integral to the shotgun barrel . </P> <P> Chokes may be formed at the time of manufacture either as part of the barrel, by squeezing the end of the bore down over a mandrel, or by threading the barrel and screwing in an interchangeable choke tube . Chokes may also be formed even after a barrel is manufactured by increasing the diameter of the bore inside a barrel, creating what is called a "jug choke", or by installing screw - in chokes within a barrel . However implemented, a choke typically consists of a conical section that smoothly tapers from the bore diameter down to the choke diameter, followed by a cylindrical section of the choke diameter . Briley Manufacturing, one maker of interchangeable shotgun chokes, uses a conical portion about 3 times the bore diameter in length, so that the shot is gradually squeezed down with minimal deformation . The cylindrical section is shorter, usually 0.6 to 0.75 inches (15 to 19 mm). </P>

What do the chokes do on a shotgun