Remington designed their 6.8mm Special Purpose Cartridge (SPC) to have improved terminal performance over the 5.56mm NATO cartridge which the U.S. military currently uses. This cartridge was specifically designed to perform better when fired from carbines and Short Barreled Rifles (SBR). Remington collaborated with Special Ops troops and the Army Marksmanship Unit to develop the 6.8 SPC. Development began in 2002 and field trials took place in 2004. The military did not adopt the cartridge, but field trials did show an interest in returning to a larger caliber rifle for applications other than sniping.
Based on a .30 Remington, rimless bottleneck case, the 6.8mm SPC has been necked down to take a 0.277" diameter bullet. Bullet weights range between 85 and 140 grains. The 115 grain bullet is the most common, and it was this bullet with a Full Metal Jacket that military trials demonstrated to had the best combination of reach and lethality. The 6.8 SPC handily outperforms the 5.56 NATO and the 7.62x39 with over 1,000 foot pounds of energy persisting at 300 yards, and an accuracy of one MOA still being found beyond 600 yards.
Other advantages of this cartridge include the fact that it fits into a magazine designed for AR-15 type rifles, operating pressures are lower than the 5.56 NATO, and the trajectory is comparable to the flat shooting 7.62x51mm NATO. To fire this cartridge in an AR-style rifle, all that is required is changing the bolt, barrel and magazine. In M4 style rifles, the 6.8mm SPC cartridge delivers 44% more energy at ranges up to 300 yards than a bullet from the 5.56mm NATO. An interesting fact that speaks to the success of the design of this cartridge is that barrel length only has a limited affect on projectile velocity and very little apparent difference in accuracy. 6.8mm SPC rounds fired from 16 inch barrels have almost the same velocity as rounds fired from 22 inch barrels.
While not likely to replace the 5.56 NATO for military use in the near future, the 6.8 SPC has been gaining a following in the civilian market. It is especially popular among hunters of deer and feral hogs since the 6.8 SPC has an effective range as far out as 300 yards, even when fired from an AR style rifle with a sixteen inch barrel. Ammunition manufacturers are meeting the demand for this cartridge by producing their most advanced bullets for the 6.8 SPC. This includes Federal's Fusion bullet Federal and Hornady's V-Max bullet.
Law Enforcement agencies are considering the Remington 6.8mm SPC as a new cartridge for their duty rifles, the majority of which are chambered in .223 Remington or 5.56 NATO. The United States Drug Enforcement Administration, notably, has been permitting its agents to buy and used AR-15 style rifles chambered in 6.8mm SPC.