The Barrett REC7 (designation stands for "reliability-enhanced carbine") is an American firearm manufactured as a selective-fire fully-automatic and semi-automatic rifle by Barrett Firearms. It is an M4 carbine utilizing a short-stroke gas piston system. REC7 is available in either 5.56×45mm NATO or 6.8mm Remington SPC. The REC7 is Barrett’s second AR-pattern rifle chambered for the 6.8mm Remington SPC cartridge, the first being the Barrett M468 rifle. The 6.8 SPC-chambered M468 rifle employed the same direct gas-impingement system as the M4. Design and features Unlike possible replacements for the M16/M4 such as the now canceled XM8, the REC7 is not an entirely new rifle, instead it is made up of an upper receiver that is attached to an M16/M4 lower receiver and is compatible with many accessories intended for the M16/M4 family. It can also be mated to M16/M4 lower receivers currently in the possession of the US military. The rifle uses a short-stroke gas piston mechanism, unlike the M16 or M4 which use direct impingement. In addition, the REC7 uses the new 6.8mm Remington SPC (6.8×43mm) cartridge, a round that is of roughly equivalent length to 5.56×45mm NATO ammunition, so it is compatible with a standard-size lower receiver currently in use by the United States military. The REC7 uses a short-stroke gas piston designed by Barrett. It rides above the barrel and is housed inside the fore-end. The spring-loaded piston is a one-piece 17-4 stainless steel rod. The forward and rearward movement of the piston is approximately one inch. Like many AR-15 type rifles, such as the M16/M4, the barrel is threaded to allow muzzle attachments such as a suppressor. The REC7 employs a free-floating Daniel Defense rail system, which allows many military accessories such as a bipod, night vision devices, and combat optics to be placed on the rifle. The REC7 features forged 7075 aluminum upper and lower receivers that are hard-coat anodized a deep black. The lower receiver has a single-stage trigger, a Magpul enhanced trigger guard for firing with gloves, and a beveled magazine well for rapid magazine changes. The upper receiver is flat-top with a Picatinny rail. The barrel is chrome-lined and is fitted with a M16A2 flash suppressor, a six-position Magpul MOE butt stock and pistol grip. The REC7 outfitted in a shortened barrel PDW configuration was one of the weapons displayed to U.S. Army officials during an invitation-only Industry Day on November 13, 2008.