↬ What do the numbers mean on a choke tube? Choke tube numbers are usually found on the outside of the choke and can be confusing if you haven’t seen them before.
The numbers on a choke tube indicate the constriction of the choke tube to a thousandth of an inch. For example, the numbers written on a modified choke tube will be 0.705”. This number is the inner diameter of the choke and can be verified by measuring the choke with a bore micrometer.
Numbers on choke tubes are a quick way to visually identify the choke size without having to measure the inside diameter. Other numbers that may be listed on a choke tube include the gauge of the shotgun, brand, and model number.
What do the numbers mean on a choke tube?
Numbers on a choke tube indicate the size of the choke. The diameter of a choke tube is written with a decimal place followed by three numbers. These numbers indicate the diameter of the choke to a thousandth of an inch.
Choke tube numbers are etched into the choke just below the threads. If a choke tube doesn’t have numbers on it, the notches or lines at the top of the choke could also indicate the constriction. Check out this guide for identifying the notches on choke tubes.
12 Gauge Choke Tube Numbers
| 12 Gauge Choke Type | Diameter |
|---|---|
| Cylinder | 0.729 |
| Skeet | 0.719 |
| Improved Cylinder | 0.716 |
| Modified | 0.705 |
| Improved Modified | 0.695 |
| Full | 0.685 |
20 Gauge Choke Tube Numbers
| 20 Gauge Choke Type | Diameter |
|---|---|
| Cylinder | 0.625 |
| Skeet | 0.621 |
| Improved Cylinder | 0.603 |
| Modified | 0.595 |
| Improved Modified | 0.590 |
| Full | 0.585 |
16 Gauge Choke Tube Numbers
| 16 Gauge Choke Type | Diameter |
|---|---|
| Cylinder | 0.673 |
| Skeet | 0.665 |
| Improved Cylinder | 0.661 |
| Modified | 0.657 |
| Full | 0.624 |
10 Gauge Choke Tube Numbers
| 10 Gauge Choke Type | Diameter |
|---|---|
| Cylinder | 0.775 |
| Improved Cylinder | 0.768 |
| Modified | 0.758 |
| Full | 0.740 |
| Turkey | 0.730 |
For choke sizes of other gauges and brands, see this chart.
Examples
The most common number on a choke tube is the choke size or diameter. Both factory and aftermarket choke tubes will show the diameter of the choke etched into the outside wall of the choke. Additional numbers can include the shotgun gauge and brand specific markings.
In order to read the numbers, the choke tube will need to be removed from the barrel. This can be done with a choke wrench by unscrewing the choke in a counterclockwise direction. Some extended choke tubes have the choke size written on the exposed portion of the choke just forward of the end of the barrel.
More Choke Tube Markings
There are over 30 different choke tube markings used for choke identification. Below are the most common markings. Please click the links below to see what each choke tube marking means.
Choke Tubes Without Numbers
The numbers on a choke tube can become worn or illegible over time. Assuming there are no other identifiable markings, such as lines or notches, the only way to determine a choke size at this point is to measure the inside diameter of the choke with calipers or a bore size tool. If you dont have a bore micrometer, consider calipers like the Mitutoyo 500. It’s a high precision option trusted by many gunsmiths for exact measurements.
Another way to determine choke size is to look for markings on the end of the choke. Vertical lines can designate the choke size without having to remove it from the barrel. Worn lettering, etching, and raised indentions are examples of other hard to see markings that could require a closer inspection.
Bottom Line: Choke Numbers Mean The Diameter
The numbers on a choke tube reference the size of the choke. These measurements are the inner diameter and are listed to a thousandth of an inch. Choke tube numbers are found on the outer walls of the choke, along with choke system and brand markings. The choke may need to be removed to see the these markings.
Popular 12-gauge choke numbers are Cylinder (0.726), Skeet (0.721), Improved Skeet (0.716), Improved Cylinder (0.711), Light Modified (0.706), Modified (0.701), Improved Modified (0.696), Light Full (0.691), Full (0.686), and Extra Full (0.681).
If a choke tube doesn’t have any markings, or numbers have worn off with time, measuring the inner diameter with calipers or a bore micrometer is the most accurate way to determine choke size. The diameter can then be compared to the numbers in this chart.
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- Complete Guide to Identifying Choke Tube Sizes
- Choke Tube Diameter and Constriction Table
- What do the numbers mean on a choke tube?
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