The Steyr ACR was an experimental assault rifle developed by Steyr for the U.S. Army’s Advanced Combat Rifle (ACR) program in the late 1980s. Unlike conventional rifles, it fired small fin-stabilized flechettes housed in a plastic sabot rather than standard bullets. The weapon used a smoothbore barrel and a gas-operated mechanism, with the goal of increasing hit probability at longer ranges by producing extremely high projectile velocity and a flatter trajectory... that being said, it never really gotten much approval from the US trials against the other competitors like the G11 or the Colt ACR.
The ACR comes with a single or a three round burst, with its high rate of fire, one can assume that it's gonna hurt when you sling some sharp needles at the enemy.
Thank you Tweedy for the model!