Shotgun chokes are used to alter the pattern of the shot. A choke constricts the shotgun bore at the barrel's muzzle. The amount of choke constriction applied to the barrel changes the tightness of the pattern produced. The higher the constriction the tighter the pattern. Increasing the choke size generally increases the recoil or "kick" of the shotgun when fired. Altering the choke size will change the pattern of the shot produced by the gun but will not increase the speed at which the shot exits the barrel or the force of the pellets on target.
Inspect the barrel for choke size stamping. Barrels with built-in chokes will usually have the choke size stamped directly on the barrel. The stamping is generally located in front of the action on the outside of the barrel in the location where the round is chambered.
Use a choke removal tool to unscrew the choke from the end of the barrel. Read the stamping on the choke. The choke size on removable chokes is stamped on the outer edge of the choke and is visible once unscrewed from the barrel. Fixed choke barrels will not have removable chokes.
Shoot the shotgun at a 30-inch-diameter target to pattern the pellets. Shoot at the target center from 40 yards away using a shell with a known number of pellets. Most factory loads will specify the number of pellets contained in each shell. The greater the choke constriction, the more pellets will hit the target. Compare the results to the following guidelines for choke sizes: 75 percent or more pellets strikes on target indicate a full choke; 73 percent indicates improved modified choke; 67 percent indicates a modified cylinder choke; 57 percent indicates modified cylinder choke; 53 percent indicates a skeet choke; and 40 percent indicates a cylinder choke.
Insert a choke gauge, sized for your gauge of shotgun, into the muzzle of the barrel. A choke gauge has graduated sizing and will indicate the choke size in place by how deep the gauge can be inserted into the muzzle. Read the line on the outer edge of the choke gauge corresponding to the amount of gauge inserted into the barrel. The line indicates the choke size.
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