It is a gas-piston operated rifle, using the revolutionary bullpup design (magazine and action located behind the trigger), and allows M16A2 length barrel, in an overall package the size of an M4A1 carbine. The stock is made of high-strength polymer, and has endured being run over by a Unimog over 30 times. The reciever is made of aircraft-grade aluminum casting, and either houses a 1.5x optic, or an optic rail. Barrels and receivers are fully interchangeable. Barrels include a 16" carbine, 20" rifle, and 24" HBAR (Heavy Barreled Assault Rifle), with a bipod. The magazines are made of translucent polymer, and can hold either 30 or 42 rounds.
Select fire is accomplished by a "pull through" trigger system: half-pull is semi-automatic, complete pull is full-automatic. There is a distinct stopping point between the pulls so that accidental discharge of full-automatic is rare.
AUG A1-receiver housing has either a 1.5x optic or rail mount
AUG A2-receiver housing has a removeable 1.5x optic or rail mount
AUG A3-essentially an AUG A2 with a RIS system.