What is a Shotgun Choke?
A 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 to .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 any shooting activity.
Shotgun Patterns:
Patterns are normally expressed as a percentage such as 50%. This means that 50% or 1/2 of all shot in any given shell will hit inside a 30 inch circle on the target. This percentage is found by dividing the number of pellets inside the 30 inch circle by the total number of pellets in the shell. The patterns are always assumed to be measured at a distance of 40 yards. The exceptions to this are cylinder and skeet1 chokes in all gauges and .410 bore shotguns in all choke sizes. These are measured at a distance of 25 yards. The chart can be used as a general guide.
The 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. Also be advised that almost anything you change in the shell will also change the pattern. High velocity or mag loads normally do not pattern as well as lighter loads. The same load by different ammo 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. 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 actually pattern it with the different loads you use and try different chokes to get the pattern you want.
| 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 or more | .045 or more |
Steel Shot:
As a general rule, when using large diameter steel shot, you would use one full degree less choke than with lead shot. For example, if you want the effects of an Improved Cylinder choke with steel, use a Cylinder Bore choke tube. Or, is you want the effects of a Modified choke with steel, use an Improved Cylinder choke tube. Want the effects of a full choke with steel, use a Modified choke tube.
Steel shot that is smaller than BB size may take an improved modified choke to get a full choke pattern.
WARNING!: Do not use BBB-T-F size shot with any choke tighter than modified.
Bismuth shot.
Bismuth shot may be used with the same chokes as lead shot.
Tungsten iron shot
Tungsten iron shot should be used with the same chokes as steel shot.
Tungsten Polymer shot
Tungsten polymer shot may be used with the same chokes as lead shot.
Tungsten Nickel (Hevi Shot)
Hevi shot may be used with the same chokes as lead shot.