Sub-caliber ammunition (also spelled subcaliber) is firearm ammunition where the projectile has a smaller diameter than the bore of the

gun barrel A gun barrel is a crucial part of gun-type weapons such as small arms, small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high ...

from which it is fired. Firing sub-caliber ammunition has several potential benefits compared to full-caliber ammunition. It can for example allow for much higher muzzle velocities due to smaller lighter projectiles being fired from relatively larger propellant charges, but it can also lower the cost of ammunition due to less material being used to produce the round compared to a full-caliber ammunition etc. Several methods exist for firing sub-caliber ammunition.

Sabot method

The most traditional way to fire sub-caliber ammunition is to fit the projectile with an expendable sabot. The sabot is a device which fills out the missing caliber when the projectile is fired and then leaves the projectile once it has left the barrel. File:Sabot Diagram Example.png, Diagram of the sabot method

Saboted sub-caliber ammunition types

Armour-piercing discarding sabot Armor-piercing discarding sabot (APDS) is a type of Rifling, spin-stabilized kinetic energy penetrator, kinetic energy projectile for anti-armor warfare. Each projectile consists of a sub-caliber round fitted with a Sabot (firearms), sabot. The co ...

(APDS) *

Armour-piercing fin-stabilized discarding sabot Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds a ...

(APFSDS) *

Saboted light armor penetrator The saboted light armor penetrator (SLAP) family of firearm ammunition is designed to penetrate armor more efficiently than standard armor-piercing ammunition. In the US it was developed by the Marine Corps during the mid/late 1980s and was approv ...

(SLAP) *

Flechette A flechette or flèchette ( ) is a pointed, fin-stabilized steel projectile. The name comes from French (from \''wikt:flèche, flèche''), meaning "little arrow" or "Dart (missile), dart", and sometimes retains the grave accent in English: flè ...

(not necessarily a sub-caliber projectile) *

Shotgun shell A shotgun cartridge, shotshell, or shell is a type of rimmed, cylindrical (straight-walled) ammunition used specifically in shotguns. It is typically loaded with numerous small, spherical sub-projectiles called shot. Shotguns typically use a ...

( the wad is considered a sabot in some countries)

Flange method

A common method during

World War Two World War II or the Second World War (1 September 1939 – 2 September 1945) was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilisi ...

, often called the ''Gerlich-'', ''Littlejohn-'' or ''tapered bore'' principle, was to fit sub-caliber ammunition with soft metal

flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of a steel beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer o ...

s filling out the missing caliber and then fire them from

squeeze bore A squeeze bore, alternatively taper-bore, cone barrel or conical barrel, is a weapon where the internal gun barrel, barrel diameter progressively decreases towards the muzzle (firearms), muzzle, resulting in a reduced final internal diameter. Thes ...

barrels. Squeeze bore barrels, often found on

shotgun A shotgun (also known as a scattergun, peppergun, or historically as a fowling piece) is a long gun, long-barreled firearm designed to shoot a straight-walled cartridge (firearms), cartridge known as a shotshell, which discharges numerous small ...

s (see

Choke (firearms) A choke is a tapered constriction of a firearm gun barrel, barrel at its muzzle (firearm), muzzle end. Chokes are most commonly seen on shotguns, but are also used on some rifles, pistols, or even airguns. Notably, some .22 LR match rifles have a ...

), progressively decreases its bore diameter towards the muzzle, resulting in a reduced final bore. When fired the flanges on the projectile would fold inwards as it travels through the reducing inner diameter of the squeeze bore. File:Squeezebore Diagram Example.png, Diagram of the flange method

Flanged sub-caliber ammunition types

Armor-piercing composite non-rigid Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, and vehicle armour. The first, major application of armour-piercing projectiles was to defeat the ...

(APCNR) *Armor-piercing non-rigid (APNR)

Sub-caliber barrel

A third method is to simply fit a smaller barrel into the original full caliber weapon which then allows the firing of smaller caliber cartridges. This is called

sub-caliber training Sub-caliber training is used to save wear and expense when training with a larger gun by use of smaller weapons (sometimes, but not always, with very similar ballistic characteristics). The smaller weapons could be inserted into the larger weapo ...

and it is used to lower the cost of training with large caliber weapons by allowing them to fire cheaper lower caliber ammunition and to not put wear on the original barrel.

References

Notes

{{DEFAULTSORT:Sub-Caliber Ammunition Ammunition