Developed in the late 1990s by ST Kinetics (formerly Chartered Industries of Singapore), Singapore was looking for a replacement to the out of date M16S1 that was in active service since 1973. Given the option of either purchasing the newer M16A2 or creating their own rifle, they decided to create a weapon that would easily fit their Army's physical attributes, rather than off the shelf weapons. The SAR 21 is externally very similar to the Steyr AUG assault rifle and could very well pass off as a Steyr AUG clone to some. In 2010, an upgraded version of the SAR 21 was introduced, the SAR 21A, although the Singaporean Armed Forces have no plans to adopt it as of yet.
The SAR 21 is distributed by ST Kinetics in Singapore and by VT Systems, a subsidiary of ST Kinetics, in the United States.
Made of a rugged, high-impact polymer, the SAR 21 is a bullpup assault rifle that serves as Singapore's service rifle. The SAR 21's action is a modified version of the AR-15's action as designed by Eugene Stoner, which gives the weapon less recoil and higher reliability. The bolt is a two-lug multi-rotating bolt with a reasonably long dwell time, which gives the SAR 21 a lower rate of fire than most modern assault rifles. The SAR 21 can accept its own proprietary 30-round translucent magazines, and can also accept STANAG-compliant magazines as well. Barrels are cold hammer-forged and come with either 1:12" or 1:7" rifling as standard. The weapon has an adjustable gas regulator which can be adjusted by a flat-head screwdriver or something similar, or if need be, can be unlatched and then turned by hand with the aid of a knurled surface. The gas regulator is used in the event of sluggish operation due to fouling. The weapon's charging handle is located on the top of the rifle, and can be rotated left and right, making the weapon somewhat ambidextrous.
The weapon is select-fire; the selector switch is of a push-button type and is located in the buttstock of the weapon. Pushing the selector switch out sets the weapon to fully-automatic while pushing it back in sets it to semi-automatic. The weapon's safety switch is located on the right hand side of the weapon, on the handguard which is attached to the pistol grip.
The SAR 21 comes with an integrated 1.5× scope as standard, though later versions ditch the integrated scope in favor of Picatinny rails. The factory-zeroed scope is meant to help in target acquisition, particularly under conditions with minimal light. The scope can be zeroed further to suit different users.
The SAR 21 is also notable as being the first weapon of its type to come with a laser aiming device as standard, powered by a single AA-sized battery located under the main foregrip. The laser aiming device has a 5-position switch located on the left handguard which can emit a beam at high or low power. When holding the weapon at ready, the left hand naturally rests on the button, which turns the light on.
Various patented safety features are also implemented into the SAR 21, such as an overpressure vent and a cheekrest made of Kevlar which helps to protect the shooter in the event of either a catastrophic failure or a chamber explosion.
When originally drafted into service in the Singaporean Armed Forces, users who were already experienced with using their M16S1 service rifles had problems with using the SAR 21. Some problems encountered included the position of the magazine well (the weapon was of a bullpup design, so it required multiple rather awkward hand changes to get a magazine out of the rifle or back in, as opposed to not needing any hand changes for the M16S1), the position of the selector switch (the M16S1's was a thumb selector), the sluggish trigger pull (the M16S1 had a crisp trigger pull) and the weapon's weight among other things. Later production models of the SAR 21 have addressed these criticisms, such as using a stiff sliding plate to improve the SAR 21's sluggish trigger pull, and a new set of handling procedures were also implemented with the use of the SAR 21s, such as the pistol grip be always held by the user's master hand.
- SAR 21 LMG
Light machine gun variant fitted with a heavy barrel. Fires from an open bolt.
- SAR 21 Sharpshooter
Identical to the standard variant, but has a 3× scope as opposed to the 1.5× scope as standard.
- SAR 21 GL (Grenade Launcher)/40 GL/M203
- SAR 21 P-Rail
Standard variant equipped with Picatinny rails. The charging handle has been moved to the left hand side.
- SAR 21 MMS (Modular Mounting System)
Modular variant with four Picatinny rails to mount various accessories. The charging handle has been moved to the left hand side, as with the P-Rail variant.
- LWSAR 21/SAR 21 LW/SAR 21 Lightweight Carbine
Shortened carbine version of the SAR 21.
- SAR 21A
Updated and lightened variant of the SAR 21. Has a full Picatinny rail running along its length and has a substantially higher rate of fire at 900 RPM.
- RCF Module (Round Corner Firing)
- The SAR 21 MMS is known for appearing in the video game Battlefield 4.