A shotgun choke is simply a tapered constriction of the gun's bore at the muzzle end. The length of this constriction varies between the different shotgun makers but usually is not less than 1.5 nor more than 3 inches. This constriction is normally from .005-.045 (thousandths) of an inch, but in the case of special purpose tubes, it can be as much as .100 (thousandths) under bore size. With screw in chokes you can very easily change the degree of constriction by simply changing the choke. This allows the use of one shotgun for almost an shooting activity.

Patterns are normally expressed with a name such as improved cylinder or as a percentage such as 50%. The patterns are always assumed to be measured at a distance of 40 yards. The exceptions to this are cylinder bore and skeet 1 chokes in all gauges and .410 bore shotguns in all choke sizes. These are measured at a distance of 25 yards. The following chart can be used as a general guide.

Name	#%	Constriction
Cylinder Bore	40	.000
Skeet 1	50	.005
Improved Cylinder	50	.010
Skeet 2	55	.015
Modified	60	.020
Improved Modified	63	.025
Full	65	.030
Extra Full	68	.040
Super Full	70	.045
Turkey	70+	.045+

The above chart is based on using premium field loads with #8 shot. Generally the larger size of shot you use the less degree of choke is needed to get an equivalent size pattern. High velocity or magnum loads normally do not pattern as well as lighter loads. The same load by different ammunition manufacturers may not pattern the same. As you can see, there are many things that can cause a shotgun to shoot a different pattern with the same choke constriction. Most chokes will shoot a pattern reasonably close to the marked size, but the only way to be absolutely sure of what your gun is doing is to "pattern" it. Use the loads you plan to shoot and try different chokes to get the pattern you want.

Steel Shot
  •  As a general rule when switching from lead to steel shot you would use a choke with one full degree less constriction.
  •  If you want a full pattern with steel use a modified choke.
  •  If you want a modified pattern with steel use an improved cylinder choke.
  •  If you want an improved cylinder pattern with steel use a cylinder or skeet choke.
  •  Do not use any choke tighter than modified constriction with steel shot unless the choke is specifically marked for use with steel shot.

Bismuth Shot
  •  Use the same choke you would use with the appropriate size of lead shot.

Tungsten Alloy Shot
  •  There are several different alloys available. These can vary to a large degree in their level of hardness. When using factory chokes I suggest you use nothing tighter than full choke unless it is approved for tungsten shot.

As a general rule most Trulock chokes are rated for Hevi Shot, Hevi 13, Federal Heavyweight and Winchester Hi Density tungsten alloys.

They identify the degree of the choke. See our Choke identification page for more information.

Beretta uses three different chokes, Mobil, Optima, and Optima Plus.

Beneilli uses three different chokes, Mobil, Crio, and Crio Plus.