The 5.56×45mm SCF (short for Synthetic Cased Flechette) was an experimental military cartridge developed by Steyr Mannlicher for use in their entrant in the Advanced Combat Rifle program.
Details[]
The cartridge is of a telescoped configuration, which means that the projectile is embedded within the casing and surrounded by the propellant. The projectile is a 9.85 grain (0.638 grams), fin-stabilized steel flechette encased in a four-part plastic spindle sabot. The cartridge has a side-initiating peripheral primer in an aluminum ring, and the casing is made of polymer. The use of this lightweight material made the cartridge weigh in at around 5 grams, less than half as much as the standard 5.56×45mm M855 round. When fired, the flechette would ride the sabot until it leaves the ACR's barrel, at which point the pieces of the sabot would disperse due to a slow, slight spin of 1 in 85 inches thanks to the ACR's very slight rifling. This also caused the flechettes to spin very slowly as they traveled, providing additional stabilization.
Tests had shown that because of the flechette's flatter trajectory, lower recoil, and lighter weight compared to the standard M855 projectile, it outperformed the M855 with its higher flight speed when zeroed in at 600 meters.
Drawbacks[]
There were drawbacks, however. When the sabot leaves the barrel and disperses, the pieces would be a potential safety hazard to friendly troops or the shooter, bouncing off the ground when firing in prone.
Along with that, due to inconsistencies in the strength of the plastic casings, which deformed from external forces, the flechette tends to leave the cartridge at varying pressures. This, in turn, leads to varying muzzle velocities and changes in trajectory from shot to shot, negatively affecting accuracy. Steyr responded to this problem by experimenting with different materials and combinations of methods.
Another problem laid in the high production costs of these cartridges, meaning that very few countries were interested in them. In addition to this, is that even though spent casings eject from the bottom side of the ACR, the hot plastic can potentially burn the shooter in the wrists, so they would have to wear gloves to protect their wrists.
Gallery[]
See also[]
External Links[]
- cartridgecollector.net page on the 5.56×45mm SCF
- patronensammler.de patrone des monats (German)
- Municion.org page on the 5.56×45mm SCF (Spanish)
- Forgotten Weapons Video: Steyr ACR: A Polymer Flechette-Firing Bullpup From the 90s
- Cartridge Collector
- Steyr ACR Flechette - whole and sectioned
- Docdroid PDF Advanced Combat Rifle program