Flechette
For the film producer, see Flechette (company).The word
flechette is
French and means "
dart" (literally, "little arrow"). It is a projectile having the form of a small metal dart, usually steel, with a sharp-pointed tip and a tail with several vanes to stabilize it during flight.
Flechettes were first used as an air-dropped weapon in
World War I by combatants on both sides. These were about four inches long ( 10 cm) and weighed a couple of ounces (60 g). Dropped from an
airplane over enemy
trenches, these gravity missiles were capable of penetrating a helmet and the wearer's skull. Similar weapons were 'Lazy Dogs' (or 'Devil Dogs'), used by the US in the Korean and Vietnam Wars. These 1 3/4" diameter (4.5 cm) bomblets were air-dropped at height in canisters by aircraft, or scattered from buckets by helicopter crews, reaching high sub-sonic speeds as they fell. Targeted at enemy personell and unarmored vehicles, the flechette hit the targets with the force of a bullet.
Smaller flechettes were used in special
artillery shells called "beehive" rounds (so named for the very distinctive whistling buzz made by thousands of flechettes flying downrange at supersonic speeds) and intended for use against troops in the open. They were used in the
Vietnam War by artillery gunners to defend their positions against infantry attacks.
Legal issues
The use of artillery flechette rounds has recently been criticised due to their use by the
Israel Defense Forces in the
Gaza Strip. Due to the wide area of effect, and their use in areas with large civilian populations, the rounds are said to conflict with the
Fourth Geneva Convention provisions protecting non-combatants. Note that the criticism is not directed at the muntitions themselves, which are not mentioned in the convention, but rather their use in civilian populated areas.[
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An APFSDS round discarding its sabot shortly after leaving the muzzle |
Known by most forces as
discarding sabot rounds, these anti-tank rounds can be more effective than
high explosive devices; see
kinetic energy penetrators. For reasons why a smaller diameter projectile is desirable, see
external ballistics and
terminal ballistics.
The
M1A1 (The US Army Main Battle Tank) and the
Challenger (the British Army MBT) both employ APFSDS (Armour-Piercing, Fin-Stabilised, Discarding Sabot) rounds as their primary AT capacity, fired from a 120-mm main gun. The
MGM-166 LOSAT was a man-portable APFS anti-tank system whose development was cancelled in 2004 due to cost-effectiveness issues.
Controversy
Modern anti-tank penetrator rounds are most effective when made with the highest density materials practical, and a common choice is
depleted uranium, or
DU. The controversy involves the residue of the use of DU rounds. DU is chemically very reactive, and the force of impact causes the DU to ignite and burn. The resulting ash of
uranium oxides is highly toxic and mildly
radioactive, and the health effects of exposure to this is still under debate. See the article on depleted urainum for more information.
In the
1960s the
U.S. Army began early developmental work on a flechette rifle cartridge. It fired steel darts that looked very much like steel nails with fins stamped into the back. The flechettes were 3â€"5 cm long, and 1â€"2 mm in diameter, with a 4â€"5 mm fin diameter. It was never fielded. Attempts have been made to develop a
selective-fire flechette several times since, with mixed results. There were also experimental flechette rounds for the
M203 grenade launcher and the 12-gauge
shotgun, but the military eventually decided that standard ammunition worked best in both.
Flechette rounds were developed for
small arms for a number of reasons. Being very small and light compared to traditional jacketed lead or steel bullets, flechette
ammunition weighs less per round, and thus an infantryman can carry more. Second is the issue of recoil--for the same amount of
kinetic energy, a lighter bullet (with a higher
muzzle velocity) produces less
recoil, and thus less shot dispersion in automatic fire. The last reason was the emergence of lightweight, flexible body armor for the average infantryman. A very high velocity, small diameter projectile is able to easily penetrate body armor. Also its mass-to-piercing-area ratio was much better than that of regular bullets.
However, the flechette has a number of weaknesses that limit its effectiveness as small arms ammunition. They tended to penetrate heavy armor less effectively than heavier, higher
momentum rifle bullets. Their extreme light weight caused them to be deflected extremely easily; a single leaf, or even a raindrop, could destabilize a flechette and cause it to tumble wildly. Because of the hard nature of the flechette, it does not deform on impact, and while it penetrates extremely well, it produces very little tissue damage. Since the purpose of firing at an opponent is to disable them, either by wounding or killing, projectiles that wound targets less are less productive. The last issue with small arms flechettes is accuracy. To fire the finned flechette out of a smoothbore requires the use of a
sabot. Since flechettes do not work well when spun by
rifling, the only source of stabilization is the fins. When the sabot separates, it can disturb the effectively unstabilized flechette, and cause deviations in its flight.
An interesting variation of the flechette that addresses its difficulties is the
SCIMTR, developed as part of the
CAWS project. Also, in 1989 and 1990 the U.S. Army experimented with the
Steyr ACR. However, the rifle did not achieve the necessary performance to be considered a viable avenue to pursue.
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Pictures of air dropped flechette, from WWI through the
1970s.
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Israeli Supreme Court decision on the use of flechette rounds in the Gaza Strip; the petition to ban their use was rejected by the court.
