The choke of a shotgun barrel works in large part the same as a nozzle of a hose. When the nozzle is tightened, water forms a stream and is projected further out. When the nozzle is opened, the spray becomes wider, and the water travels a shorter distance.
Even though manipulating the nozzle changes the stream, the amount of water flowing through the hose does not change; only the width of the nozzle opening does. In the same context, the shot pattern is changed by narrowing the size of the bore diameter at the muzzle of a shotgun.
Shotguns throughout history have been made with a wide variety of choke tube boring sizes, although recently fixed choke systems tend to be few and only regulated to single shot shotguns. Most newer guns tend to favor choke tube systems that allow for the interchanging of choke tubes in a quick manner.
The effective shooting range for a choke bore is often determined by the distance where at least 60 percent of the shot falls within a 30-inch circle. This is estimated to be 25 yards for improved cylinder, 35 yards for modified, and 40 yards for a full choke.
Recommended chokes and game type:
Improved Cylinder: Dove, Quail, Rabbit, Woodcock
Modified: Pheasant, Ducks and Geese Over Decoys
Full Choke: Pass Shooting Waterfowl, Turkey, Sandhill Cranes, Coyote
Advantages to bore diameter can be gained from shooting a double barrel or over/under shotgun that allows for two different choke sizes. Interchangeable barrels are another option for fixed choke systems. Additionally, adjustable choke systems can provide quick options for picking the correct choke tube for a particular situation.
Popular waterfowl shotguns come in standard barrel lengths of 26, 28, 30, and 32-inches. The longer barrels are geared toward goose hunting and long-range pass shooting. Shorter barrels, even down to 24-inches are used for improved handling in tighter situations such as duck blinds or timber hunting.
Ribs are usually attached to the barrel of a shotgun and are either vented or solid. The raised surface of the ribbing adds a better sight plane than the barrel itself. The ventilated rib allows for the barrel to cool off quicker in situations such as trap shooting where many rounds are fired, and the barrel can get quite hot. The vent rib allows for heat to be channeled out of the surface slots and away from the barrel.
Understanding how choke tubes work and what to expect while hunting can make the difference between a successful hunt and going home empty handed.