A duck hunter from Illinois named Fred Kimble is credited with the invention of the choke tube back in 1866. However, the idea of a choke tube did not start to slowly catch on until around 1959 when Winchester produced their Model 59 with a Versalite choke system. Eventually manufactures started to produce and tweak choke systems into what we have today.

Choke tubes are small tubes, usually a few inches long that constrict the disbursement of shot as it exits the barrel. The way choke is determined is by subtracting the diameter of the bore of a choke tube from the diameter of the bore of the barrel. Let’s say the diameter of the inside of a 12 gauge barrel is .720, and the diameter of the choke tube is .700. That is a .20 of an inch constriction of the shot as it exits the barrel which makes this choke a “Modified” choke size.

The chart below shows the diameter of the many different size chokes.

CHOKE SIZE 10/12/16/20 GAUGE 20/410 GAUGE
Cylinder .000 .000
Light Skeet .003 .003
Skeet .005 .005
Improved Skeet .007 .007
Improved Cylinder .010 .009
Light Modified .015 .012
Modified .020 .015
Improved Modified .025 .018
Light Full .030 .021
Full .035 .024
Extra Full .040 .027
Super Full .050 NA

This chart shows the percentage of shot that is placed inside of a 30” circle fired from various distances indicated in the three columns.

CHOKE SIZE 20 Yards 30 Yards 40 Yards
Cylinder Bore 80% 60% 40%
Improved Cylinder 100% 77% 55%
Modified 100% 83% 60%
Improved Modified 100% 91% 65%
Full 100% 100% 70%

What does all of this mean? A tighter choke, “Full” for example, will keep the pellets in a tighter pattern as opposed to “Cylinder” which will spread the shot pattern out. A Full choke would be used for making a long distance shot; since the pellets are grouped tightly they will travel farther and keep more pellets in the kill zone. A Cylinder choke will quickly spread the pellets which will provide good coverage of pellets in the kill zone for close shots.