Complete Guide to Identifying Choke Tube Sizes - WaterfowlChoke (2024)

Identifying a choke tube can be problematic when you don’t know what the markings mean, or the diameter of the choke isn’t listed. Luckily, there are several proven methods that work to identify choke tubes and find the correct size.

Shotgun choke markings can be identified using 5 simple methods. They include referencing a sizing chart to find the correct choke, counting the lines or notches, observing dots or circles on the choke, locating writing on the side wall, and using bore sizing tools to measure the diameter.

In this guide, we’ll discuss in more detail how to identify choke tube sizes and what the markings mean. Using these methods, you’ll be able to figure out what choke size you have in no time!

1) How to tell what choke a shotgun is

One of the easiest ways to tell the size of a shotgun choke is to use a handy reference chart like the one shown above. This chart lists the most common choke sizes from cylinder (open) to full (tight). Choke sizes can be shown in text, numbers, and markings which indicate the size or diameter.

The first step in identifying a choke tube is to remove it from the shotgun and observe the outside of the choke for text. Most choke tubes will have the brand and choke size written on the outside wall just above the threads.

If a choke tube doesn’t have anything written on it, the next step is to look for lines or notches at the end of the choke furthest away from the threads. For fixed choke shotguns, look for barrel markings near where it mates with the receiver. The choke size is often listed here with info on the barrel make and manufacturer.

If any identifiable markings are present, consult the choke tube size chart to see what choke you have. To see a comprehensive list of choke sizes for all brands and gauges, check out the choke tube diameter and constriction table here.

2) Look for writing on the side of the choke tube

Shotgun choke sizes are often written on the outer wall of the choke tube just above the threads. The choke brand, size, and diameter should be listed. An example is ‘INVECTOR PLUS FULL BROWNING”. This indicates the choke fits only Invector plus choke systems, has a full choke diameter of 0.700”, and is made by Browning.

It is not uncommon for writing to wear off with time. This can make identifying a choke tube even more difficult, but there are still several ways it can be done. Other markings, including lines, notches, and dots can help solve the mystery if the text has worn off.

If you can’t see any markings on the choke, try using a flashlight to closely look for any raised indentions or faded numbers. Some chokes have markings etched into the choke itself, which under bright light can reveal subtle dips and rises.

3) Lines or notches marked on the end of the choke

• 5 lines or notches (*****) – Cylinder Choke
• 4 lines or notches (****) – Improved Cylinder
• 3 lines or notches (***) – Modified Choke
• 2 lines or notches (**) – Improved Modified
• 1 line or notch (*) – Full Choke

Notches or lines on a choke tube indicate the size of the choke. They can be found on the top end of the choke, opposite the threads. Notches are shallow parallel lines that are grouped together and are found on most factory flush chokes, especially Browning, Winchester, and Remington.

Cylinder chokes have 5 lines or notches, the most of any choke size. Improved cylinder has 4 lines, modified has 3 lines, improved modified has 2, and a full choke only has one line or notch. It’s rare to find lines or notches outside this list, as it’s an accepted industry standard.

Many choke tubes have 4 large notches spaced equally around the top end. These are not choke size markings, but rather grooves to place a choke wrench. If a choke doesn’t have lines or notches indicating the size, but does have 4 choke tube wrench grooves, you’ll have to use another method to determine its diameter.

4) Dots or round indentions

Similar to lines and notches, some older choke tubes are marked with dots or circles. These dots are located at the top end of the choke opposite the threads and a grouped together.

Dots have the same number scheme as lines, where 5 dots are cylinder, 4 dots are improved cylinder, 3 dots are modified, 2 dots are improved modified, and 1 dot is a full choke.

Remington and several other brands will place dots on the outer wall of the choke near the text, but these dots or circles aren’t an identifying feature.

5) Measure the choke with calipers

Shotgun choke types that can’t be identified with the 4 methods already discussed leave no other option other than measuring with calipers or using a bore sizing tool. Choke tube diameter is measured to a thousandth of an inch, so finding a tool set with this precision is key.

To measure a choke tube with calipers, first make sure it’s turned on, calibrated, and reading zero fully closed. Expand the calipers outward until the tips of both sides are resting on the inner wall of the choke. Typical readings for 12-gauge chokes will be in the range of 0.730” to 0.695”.

One of the best digital calipers for measuring choke tubes is the Mitutoyo 500. It measures 0 to 6 inches in 0.0005″ increments for precision use when determining choke tube size. It’s one of the most trusted calipers for gunsmiths, so check it out if you have a choke that doesn’t have any markings on it.

Bottom Line

If you’re wondering how to tell what choke your shotgun is, then the methods listed in this guide will certainly find that out. The simplest way is to look for markings on the choke tube itself or on fixed choke barrels it will be written on the barrel near where it meets the receiver.

If the choke size isn’t written anywhere, the choke may have lines, notches, or stars on the top end furthest away from the threads. Count the lines or notches and compare them to the chart listed near the beginning of this guide. 5 lines is cylinder, 4 lines is improved cylinder, 3 lines is modified, 2 lines is improved modified, and 1 line is a full choke.

The fail proof way to identify choke tube size is to use a pair of calipers or bore gauge tool that measures to a thousandth of an inch and compare the readout to the diameters listed in this chart.

Identify a choke and want to know its diameter? See the guide here.

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Related

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• Choke Tube Diameter and Constriction Table
• What do the numbers mean on a choke tube?
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Last update on 2024-06-02 / Affiliate links / Product Images from Amazon Product Advertising API