The inside bore constriction at the muzzle end of a shotgun's barrel is known as the "choke." When a shotshell is fired, shot travels down the bore, exits the muzzle and begins to "spread out." Just as a nozzle on the end of a garden hose controls the spray of water, the choke controls the spread of shot, making it narrower or wider.

The three basic chokes for a shotgun are known as full (tight constriction and delivers a narrow, dense spread), modified (less constriction and delivers a medium-width spread) and improved cylinder (even less constriction and delivers a wide, open spread). A gun with no choke is called a cylinder bore and delivers the widest spread. There are also a number of specialty chokes that provide narrower or wider spreads - some of the most popular are for skeet shooting and turkey hunting.

A shotgun's choke also determines its effective range. The tighter the constriction, the farther the effective range. For instance, a full choke is most effective at 40 to 50 yards. An improved cylinder is most effective from 20 to 35 yards. Shotgun barrels come with either fixed (non-removable) chokes or today's more popular interchangeable screw-in choke tubes that let hunters quickly and easily change chokes to match changing shooting conditions.

Most commonly used chokes

Super-Full and Extra-Full Chokes - Known as gobbler getters, these are ideally suited for the head shots necessary in turkey hunting. They have extra-tight constrictions and the most dense patterns.

Full Choke - This has tight constriction and a dense pattern, delivering approximately 70 percent of a shell's total pellets in a 30" circle at 40 yards. Best for trap shooting, waterfowl pass shooting, turkey hunting and buckshot loads.

Modified Choke - The modified is characterized by less constriction than full choke, delivering approximately 60 percent of a shell's total pellets in a 30" circle at 40 yards. Excellent for all-around hunting of waterfowl, long-range flushing of upland birds (such as late-season pheasant and sharptail grouse) as well as other small game. Also used for trap shooting.

Improved Cylinder Choke - Even less constricted than modified, the improved cylinder distributes approximately 50 percent of a shell's total pellets in a 30" circle at 40 yards. Ideal for close-in small game shooting, upland bird hunting (such as quail, grouse and pheasant) as well as hunting waterfowl close over decoys. Rifled slugs also perform very well with this choke.

Cylinder Bore - No constriction and distributes approximately 40 percent of a shell's total pellets in a 30" circle at 40 yards. Most often used by law enforcement for service shotguns.

Skeet Choke - A specialty choke that sends approximately 50 percent of a shell's total pellets in a 30" circle at 25 yards. This type is designed to deliver optimum patterns for close-range skeet shooting.