6.8mm Remington SPC (using Sierra bullets)
Date: Jul 10 2019
The 6.8 Remington SPC was developed in conjunction with the U.S. Army Marksmanship Unit and the U.S. Special Operations, primarily to improve the terminal performance of the M4 Carbine chambered in 5.56 NATO. Most development and testing took place between 2002 and 2004, with the cartridge being formally introduced in 2005. It utilizes .277-inch bullets that are typically between 90 and 130 grains with the 100-to 120-grain versions usually offering the best overall performance. Further testing has shown that select 130-grain bullets are also top choices for hunting big game. The 6.8 SPC case was based on the .30 Remington and has a water capacity of around 35 to 37 grains. For reference, commercial Remington factory loads list various 115-grain bullets designed for hunting and match target work at 2,625 fps, but in the test rifle used here actual velocities were more than 100 fps slower than that figure.
Although the acceptance of this cartridge by both military brass and civilians has been limited, it offers very mild recoil and is fully adequate for hunting deer at moderate distances. Accuracy was excellent.
When assembling ammunition for AR rifles, the overall cartridge length should be held to 2.250 inches for reliable functioning, which is the industry specified length. There are after-market magazines that allow the 6.8 SPC’s overall length to be increased to 2.315 inches and still function, which allows for a small increase in powder capacity and velocity, but this practice is generally for specialized (usually match) ammunition to be tailored to a specific rifle.
The ogive of some bullets designed for the .270 Winchester will have an incorrect profile to allow them to be seated at the maximum overall cartridge length of 2.250 inches in the 6.8 SPC. In other words, they can contact the leade in some rifle chambers, which can increase pressures or result in a stuck bullet in the barrel if the cartridge is extracted rather than fired. If using bullets designed for the .270 Winchester, be certain that they are seated so that the ogive does not contact the leade.