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Sabot
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A sabot (: "saybow", or : "sabbow") is a device used in a firearm or cannon to fire a projectile, such as a bullet, that is smaller than the bore diameter. The term is also applied to a battery stub case, a device used similarly to make a small electrical battery usable instead of a larger one.
Since a strong seal is needed to trap propellant gasses behind the projectile, and keep the projectile centered in the barrel, something is needed to fill the gap between projectile and barrel, which is the role of the sabot. Firing a small size projectile wrapped in a sabot raises the muzzle velocity of the projectile. Made of some lightweight material (usually plastic in smallbore guns, and aluminium - and, in earlier times, wood - in cannon), the sabot usually consists of several pieces held in place by the cartridge or a loose connection. When the projectile is fired, the sabot blocks the gas, and accelerates the projectile down the barrel. When the sabot reaches the end of the barrel, the shock of hitting still air pulls the parts of the sabot away from the projectile, allowing the projectile to continue in flight.
Sabots are used to fire the flechettes that form anti-armour kinetic energy penetrators.
For reasons why a smaller diameter projectile is desirable, see external ballistics and terminal ballistics.
Sabot-type shotgun slugs were marketed in the U.S. starting in about 1985. When used with a rifled slug barrel, they offer vastly improved accuracy compared to traditional shotgun slugs. They are now legal for hunting in most states.
The name "sabot" comes from a French word for wooden shoes traditionally worn in some European countries, also called clogs.
Types of sabotsCup sabotA cup sabot merely supports the base and rear end of a projectile. When the sabot and projectile exit the muzzle of the gun, air pressure on the sabot forces the sabot to release the projectile.
Expanding cup sabotUsed typically in small arms (most commonly muzzleloaders), an expanding cup sabot has a one piece sabot surrounding the base and sides of a projectile. Upon firing, when the sabot and projectile leave the muzzle of the gun, centrifugal force from the rotation of the projectile and sabot opens up the segments surrounding the projectile, releasing it.
Base sabotA base sabot has a one piece base which supports the bottom of the projectile, and separate pieces that surround the sides of the projectile and center it.
The base sabot has better and cleaner sabot/projectile separation than cup or expanding cup sabots, but is more expensive since more pieces are involved.
Spindle sabotA spindle sabot uses a set (usually two) of matched rings which have a center section in contact with a long projectile, front sections which center that projectile in the barrel, and a rear section which both centers the projectile and seals propellant gases.
Spindle sabots are the standard western type armor piercing ammunition type. Two and three piece spindle type sabots are shown in the illustrations at the top of this article.
Shotgun slugs often use a cast plastic sabot similar to the spindle sabot. Shotgun sabots in general extend the full length of the projectile and are designed to be used in rifled barrels.
Ring sabotA ring sabot uses the rear fins on a long projectile to help center the projectile, and the multi-piece sabot forms only a single thin ring around the projectile near the front, sealing gases from escaping past it and centering the front of the projectile.
Because the rear fins have to have the same diameter as the gun bore, they typically are larger than is optimum for flight performance.
Several Soviet and current Russian design armor piercing sabot projectiles use ring sabots.
See also
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