3. Definition of choke – inside the barrel

The term choke has two definitions which, in a perfect world, would be in total agreement with one another. From the perspective of the gun, the degree of choke refers to the constriction (if any) at the muzzle compared to the internal diameter of the bore measured 9 inches ahead of the breech. By definition, therefore, a cylinder bored barrel has no choke. The other perspective of choke is the distribution of shot at the target (see later). The shooter is concerned with the latter: the gun maker the former. The English system of choke notation is detailed in the table below.

Table 5: English specifications for choke in barrels

NOTE: A barrel can be bored to any degree of choke, including ‘negative choke’ i.e. a flared muzzle.

There is no guarantee that a barrel bored to ‘¼ choke’ will throw ¼ choke patterns with any particular brand of cartridge. The only way to determine how a barrel behaves is to pattern it (fire it at a patterning plate). Just because a barrel is marked, say full choke, does not mean that it is bored to full choke. A previous owner may have had the choke opened up. Hence the only way to be sure is to measure the barrel at both ends with the proper tools and/or test the patterns it throws – see next subject.

Some European gun barrels (esp. Italian) bear ‘star’ markings to indicate the degree of choke, as shown in Table 6 on the next page. Again, these markings are indicative of dimensions only, and do not guarantee that the patterns thrown will be of corresponding density and diameter.

Table 6: Choke markings on European barrels (source: GT)

Go to the top of this page, back to shotgun barrels and ammunition, or to the firearms reference main page