New shooters may think that shotguns are shotguns are shotguns. What you may not realise is that some simple (and minor) changes to a shotgun can massively change its characteristics and effectiveness. Barrel length and ammunition type will change how the gun performs but there’s another change, one less permanent than changing barrel length, which can change the gun’s effectiveness at range.
This small modification is known as a ‘choke’.
How do they work?
A shotgun choke screws into the end of the shotgun’s barrel and modifies the ‘spread’ of the shot and therefore its effective range. The choke changes the shot’s spread by tightening the barrel (or not) at the muzzle. This effectively forces the shot into a tighter grouping, great for longer ranges but diminishing effectiveness at close range. Think about squeezing the end of a garden hose; by tightening the end of the hose, the range is increase but you must be more accurate.
Shotgun chokes also have the benefit of creating a more uniform, evenly distributed shot, ensuring that there are no gaps in its spread. A gap in the shot’s spread is a gap that can hit your target.
The effectiveness of a choke is determined by the percentage of the ‘shot’ that falls within a 30 inch (76cm) circle at a distance of 40 yards (37m). If the shotgun’s spread is so that a prospective target can be placed on the paper and covers less than 3 holes, it is deemed that the shotgun is past its effective range. This obviously does not mean that the shotgun is not lethal past this range, but its effectiveness for its task is severely reduced. Due to this, the chokes are largely based on personal preference and experience to understand which choke works best for the shooter’s needs.
A shotgun without a choke has the muzzle the same diameter the full length of the barrel, in some places this is known as ‘cylinder’. The effective range of a 12 gauge cylinder bore shotgun is stated to be 18m.
Stepping up to a 1/4 choke, known in the US as an improved cylinder choke, makes the effective range of the shotgun increase to 23m. For a miniscule barrel constriction of 0.25 millimetres (1/4 choke) the effective range of the shotgun has increased by 5 meters.
At the other end of the spectrum is a 1/1 choke, known as a ‘full choke’ in US. A 1/1 choke constricts the barrel by 0.889mm, just half a millimetre more than a 1/4 choke, however the effective range is increased to 37m. A small change of just 0.5mm in a shotgun choke is enough to double its effective range.
Chokes can be slightly more than a constriction in the barrel, however. Some chokes are designed similarly to a weapon’s compensator, with porting strategically positioned to use the expanding gases to mitigate recoil.
Other chokes have grooves parallel to the barrel that remove spin from the shot when it’s fired, giving a tighter, more uniform spread of shot. Other kinds deliberately impart spin on the shot, similarly to how barrel rifling works, however in a shotgun this is done to make the shot spread even more than before.
In certain conflicts, such as the Vietnam war, shotguns were occasionally modified to have an oval or ‘duckbill’ choke. These chokes are more constricted at the top and bottom of the barrel and wider at the sides, resulting in a shallow but wider spread for engaging multiple targets at once. However, these chokes were often unpredictable and had limited effectiveness.
Offset chokes are deliberately designed to change the point of impact of a shot. Whilst this might seem useless at first, they are particularly useful for double barrel shotguns, where the barrels are misaligned. These chokes will modify where the barrels shoot and cause them to fire consistently with one another.