Shotgun choke tubes fit in the interior of the end of a shotgun barrel. These removable tubes control the dispersion of the shot fired from the shotgun. Changing the dispersion of the shot is useful if the same gun will be used in multiple sports, such as trap and skeet, or used in hunting different species of game.
Standard chokes for a shotgun are cylinder, improved cylinder, modified, improved modified, full and extra full. Cylinder choke indicates no choke effect and is the most open choke, providing the widest dispersion of shot as it exits the barrel. Extra full is the tightest choke and concentrates the shot into the tightest pattern.
The shot fired from a cylinder choke-equipped gun will place 70% of the shot within a 75 cm (30 inch) circle at a distance of 23 metres (25 yards). The modified choke type will create a 70% shot pattern in 75 cm (30 inch) at 32 metres (35 yards). The extra full choke tube accomplishes the same thing at a distance of 41 metres (45 yards).
Advantages and disadvantages
The idea is to have the optimum shot pattern. If the optimum shot pattern occurs at 23 metres (25 yards) and the target is at 41 metres (45 yards), the shot will disperse too much to place enough shot on target. Conversely, If an extra full choke tube is used, creating the ideal shot pattern at 41 metres (45 yards), then a target at 23 metres (25 yards) will be more difficult to hit.
The first system of interchangeable chokes was developed by Winchester Firearms in 1959 but discontinued in 1965 due to problems. It was improved and reintroduced in 1970 and marketed under the Winchoke name. Other manufacturers have also developed their own line of choke tube systems.
Choke tubes are standard on some guns or can be installed by a qualified gunsmith. Some sportsmen purchase a complete set of six choke tubes while others purchase two or three tubes that fit their hunting or shooting needs.