What are the Notches on Choke Tubes

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A choke is a tapered constriction of a barrel’s bore located at the muzzle end. Its primary purpose is to shape the spread of a shot for better range and accuracy. It is designed to alter the distribution of the pellets of a shot. 

Since their invention in 1866, chokes have evolved several times. The first choke was a fixed, permanent choke that could not be changed without a full barrel swap or a gunsmith altering it. Interchangeable chokes, also known as screw-ins, were made soon after and are still commonly used today. 

Screw-in chokes create a variety of patterns to allow a single gun impressive versatility. These days, there are more guns with interchangeable choke tubes than guns with fixed choke tubes. But what are the notches on choke tubes and what do they do? Find out here.

What Choke Tube for Slugs

Implementation of Chokes

Chokes may be fixed chokes or interchangeable chokes. Fixed chokes are formed at the time of manufacture as part of the barrel. This is done by squeezing the end of the barrel’s bore down over a mandrel. Shotguns with interchangeable chokes are made at the time of manufacture by threading the barrel and screwing in an interchangeable choke tube.

Chokes may also be formed after the manufacture of a barrel. This is done by increasing the diameter of the barrel’s bore, creating a “jug choke,” or installing screw-in chokes inside a barrel. Regardless of its implementation, a choke typically consists of a conical section and a cylindrical section. The conical section tapers from the bore diameter to the choke diameter and is followed by the cylindrical section of the choke diameter.

What are the Notches on Choke Tubes?

Interchangeable chokes or screw-ins have a unique system of identification. The system of identification usually uses notches, dots, or stars. Whatever symbol is used does not matter. What matters is the number of symbols. A single star on a choke tube means the same thing as a single notch on another choke tube. 

The number of notches, stars, or dots is a means of identifying choke tubes. Some older interchangeable chokes use combinations of dots, stars, and letters. If you come across such choke tubes, visit the manufacturer’s website or check the manual to identify them correctly.

Five Basic Choke Tubes and the Number of Notches they have

Cylinder choke

Cylinder chokes are the most open chokes. The cylinder choke, also called “no choke,” is the simplest shotgun choke and it has no constriction. Screw-in cylinder chokes are identified by five notches (IIIII).

Its bore design is the original fixed bore design of shotguns. Because it has no constriction, its pattern is relatively vast. The choke distributes about 40% of pellets in a 30-inch circle at 40 yards.

Their wide pattern makes them excellent for hunting small game in thick woods or brushes where you have a small range. At 25 yards, cylindrical chokes have a pattern of about 70%. They are very effective at short range, making them excellent for home defense. Many law enforcement agents also use them for their shotguns.

Improved cylinder choke

Improved cylinder chokes have a slight constriction of 0.25mm/0.01″ barrel to muzzle. They are identified by four notches (IIII), have a pattern of about 50% at 40 yards, and have great hunting applications for upland game or close-up waterfowl. They are an excellent fit for rifled slugs for hunting medium-size or large games at 50 to 75 yards.

Modified choke

A modified choke has a moderate constriction of 0.55mm/0.02″ and is identified by three notches (III). Its constriction allows it to deliver about 60% of a shell’s total pellets at 40 yards, making it excellent for duck hunting. It’s great for hunting small game while alternating between brushes and open fields. Modified chokes can also be used with different shots, including steel and other non-toxic ammo.

Improved modified choke

This choke patterns 65% of the total pellets at 40 yards. It has a constriction of 0.635mm/0.25″ and is identified by two notches (II). They come in handy when birds are flushing and flying further away. They are also suitable for hunting small game like squirrels and rabbits.

Full choke

Full choke is the tightest of the basic five chokes, with a constriction of 0.76mm/0.03″ barrel to muzzle. The choke patterns about 70% of the shell’s total pellets at 40 yards. Full chokes are identified by one notch (I). They are designed for long-range shotgun applications. They are excellent for shooting waterfowl overhead and for turkey hunting.

choke gun and key for them isolated on white back

Most Common Specialized Chokes and the Number of Notches they have

  1. Skeet 1. Skeet is a form of moving target for shotguns made of clay. Skeet 1 is a specialty choke for skeet shooting and has a constriction of 0.13mm/0.005″ barrel to muzzle, patterns 45% at 40 yards, and 75% at 25 yards. It has a slightly tighter constriction than cylinder chokes. Instead of notches, it is usually identified as SK1.
  2. Skeet 2. Skeet 2 is another specialty used in skeet shooting. It has a slightly tighter constriction than Skeet 1, with a constriction of 0.38mm/0.015″. It patterns 55% at 40 yards. Instead of notches, it is usually identified as SK2.
  3. Extra Full. It is tighter than the ordinary full choke, with a constriction of 1.015mm/0.04″ and patterns 73% at 40 yards. It is often identified with one notch (I) and used when longer distances than a full choke are needed. 
  4. Turkey. These chokes have the tightest constriction. They have a constriction of at least 1.145mm/0.045″ barrel to muzzle and patterns at least 75% at 40 yards. As the name implies, Turkey chokes are the ideal chokes for hunting turkey. Turkeys are tougher than pheasants. To kill them cleanly, you need pellets to hit them in vital areas. 

A turkey’s head and neck are the ideal target areas because layers of feathers do not protect them. Turkeys are very wary and have acute hearing and excellent vision. Consequently, you may only have one chance to hit it. Turkey chokes also bear one notch for identification, but they almost always have a differentiating printing or stamping. Something like “TKY.”

There are other specialized chokes like waterfowl tubes, coyote choke tubes, etc., and they have their means of identification too. Identifying the five basic chokes is easy once you remember that a higher notch means less restriction and a lower notch means more restriction.

Following that logic, 1 notch = Full, 2 notches = Improved modified, 3 notches = Modified, 4 notches = Improved cylinder, 5 notches = Cylinder. Before using any choke, tubes or firing ammunition, you should check your firearm’s specifications in the user manual or the manufacturer’s website.

Final Thoughts

Now you know the answer to what the notches on choke tubes are so you can make an informed decision about everything you do with your firearm.