A sabot is a device used in a firearm or cannon to fire a projectile, such as a bullet, that
is smaller than the bore diameter, or which must be held in a precise position.
Design Since a strong seal is needed to trap propellant
gases behind the projectile, and keep the projectile centered in the barrel, something
is needed to fill the undesirable but necessary gap between projectile and barrel, a space
referred to as the windage, and this 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, 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 carries 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.
This round consists of the outer cup which holds numerous subcaliber darts.
The sabot cup holds the individual flechettes together tightly until the sabot case separates
after leaving the barrel.
For reasons why a smaller diameter projectile can be 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.
Types of sabots
Cup sabot A 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 sabot Used typically in small arms, 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, inertia from
the rotation of the projectile and sabot opens up the segments surrounding the projectile,
releasing it.
Base sabot A 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 sabot A spindle sabot uses a set 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 of armor-piercing ammunition.
Two- and three-piece spindle-type sabots are shown in the illustrations at the right of
this paragraph.
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 sabot
A 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 Shell
Armour-piercing discarding sabot Gas check
Obturate Saboted Light Armor Penetrator
External links Shotgun sabot separation photography
PLANSEE Tungsten Ammunition Components at Army Technology.com, accessed December 30,
2012