The Steyr 5.56 mm ACR is a gas operated/ rising chamber modular weapon system firing semiautomatic or high cyclic 3 round burst of flechette projectiles from a 24 double round magazine. This system combines the ultimate feature in weapon optics, and ammunition design. To ensure maximum hit probability under battlefield stress the ACR ammunition design utilizes the latest kinetic energy projectile technology: a 9.85 grain carbon steel flechette in a lightweight synthetic case. The streamlined design and fin stabilization of this 5.56 X 45 synthetic cased flechette reduces the drag coefficient and produces a highly stable projectile with excellent penetration at all ranges. Its translucent magazine allows for instant assessment of ammunition supply. Most importantly the flechette outperforms the current M16 A2 M855 by traveling twice as fast as the M855 on a completely flat trajectory when zeroed in at 600m.

The weapon and the ammunition are designed to eliminate the need to change adjustments to sighting in all conditions. Faster flight speed, flatter trajectory, lower recoil and high cyclic rate add up to systematically engineered performance for maximum hit probability under combat stress. The Synthetic Cased Flechette also weighs less than one half the weight as the SS109 cartridge allowing for increase in the number of rounds per combat load. At 600 yards the velocity of the flechette is 910 M/S allowing it to penetrate steel plate and all known body armor. (http://www.steyr-aug.com/acr2002.htm)