the gun barrel being cold hammer forged. It has a long stroke gas system and a two-lug Stoner-style bolt, boasting high reliability. The translucent magazine allows precise assessment of its current ammo load. The SAR 21 has a built-in Laser Aiming Device (powered by a single "AA-size" battery) which has a 5 position switch that emits a visible or infrared beam at high or low power. It can be set to a steady beam or a momentary beam that is triggered by a pressure switch activated with the user's left thumb. The rifle incorporates various patented safety features, such as a Kevlar cheek plate and a high pressure vent that protects the shooter in the event of a chamber explosion or catastrophic failure. The integral 1.5x optical scope that is built into its carrying handle aids in target acquisition, particularly under low light conditions. The scope is factory-zeroed, and requires minimal further zeroing to suit different users, shortening non-training range time. Design issues Early users of the weapon in the Singapore Armed Forces experienced many problems due to their unfamiliarity with the bullpup design. Their criticisms (usually compared to the M16S1 rifles they were trained with) include: the awkward position of the magazine well, and the difficulty in changing magazines, requiring multiple hand changes due to its bullpup shape the awkward position of the fire selector (located at the butt, with the action), as opposed to the thumb selector on the M16S1 the sluggish trigger pull compared with the crisp trigger of the M16S1 the heavy weight of the weapon the increased muzzle blast, due to the muzzle being nearer to the user's ears being told by instructors that it is a "right-handed only" weapon and left-handed soldiers having to (and are still being taught to) fire with their right hand iron sights that chip off easily when weapon is dropped Lack of internal illumination of the scope (the crosshairs in the scope are virtually invisible in the dark) Some of these criticisms were addressed with design modifications to the later production models. New weapon handling procedures were also introduced. The magazine changing issue was solved with training soldiers to always hold the pistol grip with their master hand. The charging of the weapon and reloading of magazines are to be done by the non-master hand. The sluggish trigger pull was improved by using a stiff sliding plate in place