to contact the forward face of the bolt carrier, causing it in turn to move rearwards. The bolt itself is of similar configuration to the AR-15 with seven radial locking lugs engaging corresponding recesses in the barrel extension, and the extractor in place of the eighth lug. The bolt is moved into and out of the locked position via a cam pin that engaged a helical slot in the bolt carrier, which rides on two metal guide rods (each with its own return spring) instead of contacting the receiver walls, providing additional clearance for foreign matter entering the receiver. Unlike the AR-15, the cocking handle fits directly into a recess in the bolt carrier and reciprocates with it during firing, allowing the firer to force the breech closed or open if necessary. The cocking handle slot has a spring-loaded cover that can be closed by the user to prevent debris entering the receiver, and it will open automatically as the bolt carrier moves rearwards after the first shot. The recoil springs are housed within the receiver, differing from the AR-15 which houses its more elaborate buffer mechanism in the buttstock. The AR-18's compact design enables the use of a side-folding stock with a hinging mechanism (which proved to be less than adequately rigid). The sights are of similar design and sight picture to those of the AR-15 - a 2-position flip aperture rear sight and post foresight - but the rear sight is made of stampings. A notable change is the use of a more conventional lower sight line closer to the axis of the bore, in contrast to the elevated sights of the AR-15. A dovetail is spot welded to the receiver in front of the rear sight for a proprietary ArmaLite quick-detachable scope mount. The magazines were of a brand new proprietary design and were different than those of the AR-15. The original magazines made by ArmaLite and Howa were of gray-anodized aluminum alloy with black-plastic followers and came in 5- and 20-round capacities. (The 5-round magazine, like that of the Colt AR-15 Sporter, was just a full-size 20-round magazine blocked to only hold 5 rounds.) They lacked the magazine-catch cutouts of the AR-15 magazines, making them incompatible. Sterling later produced black-enameled steel magazines in 20- 30- and 40-round capacities that did have cutouts and were able to feed from an AR-15. However, the AR-18/AR-180 was never capable