Barrett M468

The Barrett M468 was a variant of the M4 Carbine, rechambered for a heavier and larger 6.8mm bullet for increased terminal performance. The designation of M468 stands for an M4 carbine chambered for the 6.8mm SPC cartridge. It was an attempt to create an optimal Special Operations close-to-medium range assault carbine for Close Quarter Battle (CQB). A 12-inch barreled micro-carbine and 16-inch barreled assault carbine version were created.

Accessories
The standard M468 uses a regular forend. The M468A1 comes with an ARMS Selective Integrated Rail (SIR) accessory rail system with integral "flat-top" Picatinny Rail scope mount and 4-position forend, and a detachable ARMS Back Up Iron Sight folding rear iron sight. The Barrett gas block in front has an integral forward-folding iron front sight. The weapon could use either a solid M16A2-style stock or an optional M4-style 4-position collapsible stock and used an M16A2-style pistol grip.

The original muzzle-brake was a proprietary design with four vents (two on each side) for increased control. This was later replaced with an M16A2-style "birdcage" muzzle-brake on the later Barrett REC-7 to have it use parts already in the supply chain and have compatibility with US- and NATO-standard rifle grenades and supressors.

A proprietary Barrett-made silencer was available that was optimized for use with the 12-inch barreled version. The silencer weighed about a pound and was 12" long. The Barrett gas block contained a ratchet that steadied the silencer while it was mounted. The silencer screwed on clockwise and unscrewed counter-clockwise.

The M468 could not use the same magazines as the AR-15/M16 family, so they designed their own. The Barrett magazine was made of steel rather than aluminum and had a steel follower rather than an aluminum or plastic one. The magazine used two magazine springs instead of one to maintain steady pressure and reliable feeding. The original 28-round magazine was designed to be the same dimensions and use the same web gear as the 30-round AR-15/M16 magazines. The larger 30-round Barrett magazines were an inch longer and weighed 5 ounces more (0.569 lbs. [258 grams] empty / 1.37 lbs. [622 grams] full) than the standard AR-15/M16 magazine.

Civilian Market
The civilian-market weapon shipped with a soft carrying case, cleaning kit, sight wrench, and two 25-round PRI magazines.

Fate of the M468
The Barrett M468 rifle employed the same direct gas impingement system as the M4. The weakness of such a system is that it jets hot gases and unburnt propellant directly into the rifle’s receiver, leading to overheating and potential stoppages if regular maintenance and cleaning protocols are overlooked. The cartridge was also hotter-loaded than the 5.56mm NATO, speeding up this problem. This made the M468 less reliable than the M4 carbine it was trying to replace. Barrett was still selling its limited stock of the M468 but only as an upper receiver kit and not as a complete rifle up until 2010.

The M468 has been largely replaced by its upgraded version, the Barrett REC7. The 5.56mm NATO version of the REC-7 was submitted for the Enhanced Carbine trials for use by conventional forces.