When referring to firearms, the choke is a part of the barrel, or a tube that screws into the muzzle that constricts the barrel at the muzzle. In today’s era, chokes are very commonly used to improve performance among hunters and target shooters.
There are many manufacturers of chokes, but the way they work is the same. They alter the shot pattern made when they leave your gun. The choke keeps an increased center density at increasing distances.
Choosing the right choke for your gun and type of shooting is absolutely critical. There are many brands and dimensions that can affect your performance.
To determine the size of choke that you need, subtract the inside diameter of the choked area from the diameter of the bore. There are various amounts of constriction provided by different chokes.
Constrictions are relatively similar for 10, 12, 16, and 20 gauge shotguns, but different for the 28 and 0.410 in an effort to keep constriction percentages the same. Here is a chart that shows the difference between cylinder, improved cylinder, modified, and full choke.
“I personally stand by all my my products” -Jim Cunningham