a safety mechanism (cross-bolt, button type), located immediately above the hand grip. In its "safe" position (white dot) the trigger is mechanically disabled; pressing the safety button to the left exposes a red dot and indicates the weapon is ready to fire. Some versions have an ALO or "automatic lockout", a small projection at the base of the trigger. This was first included on the Irish Defence Forces variant of the rifle, and soon after, the Australian Defence Forces variant. In the exposed position the ALO stops the trigger being squeezed past the semi-automatic position. If needed, the ALO can be pushed up to permit automatic fire. Ammunition feeding The AUG is fed from a translucent, double-column box magazines (molded from a high-strength polymer) with a 30-round capacity and an empty weight of . The light machine gun variant of the AUG uses an extended 42-round magazine. An Argentine variant of the FN FAL chambered in 5.56×45mm NATO cartridge and known as the FALMP III Type 2 also uses the same magazine. Sights The AUG has a 1.5× telescopic sight that is integrated with the receiver casting and is made by Swarovski Optik. It contains a simple black ring reticle with a basic rangefinder that is designed so that at a 180 cm (5 ft 11in) tall man-size target will completely fill it, giving the shooter an accurate method of estimating range. The sight cannot be set to a specific range but can be adjusted for windage and elevation for an initial zero and is designed to be calibrated for 300 m. So when it is set, aiming at the centre of a target will produce a hit at all ranges out to 300 m. It also has a backup iron sight with a rear notch and front blade, cast into the top of the aluminium optical sight housing, used in case of failure or damage to the primary optical sight. The sight is also equipped with a set of three illuminated dots (one on the front blade and two at the rear) for use in low-level lighting conditions. In order to mount a wide range of optics and accessories, a receiver with a NATO-standard Picatinny rail and detachable carrying handle was also developed and introduced in December 1997. Engineering The quick-change barrel used in the AUG is cold hammer-forged by GFM-GmbH of Steyr Austria for increased precision and durability,