The 6.8mm Remington SPC
By Chuck Hawks
The inadequacies of the 5.56mm NATO as a service rifle cartridge are well documented and have inspired many suggestions regarding possible replacements (some on this web site). Apparently someone in the U.S. Special Operations Command also realized the need for a more potent round and initiated work on a new cartridge designed to work in the M16 action.
The new .270 caliber (6.8mm) cartridge is the result of at least a two year cooperative effort between Special Operations, the Army Marksmanship Unit, and Remington. Various calibers from .22 to .30 were tested before settling on a standard .277" diameter bullet, the same bullet diameter made famous in the .270 Winchester.
Remington is offering four 6.8mm SPC factory loads, all with 115 grain bullets. These include two target loads, a Core-Lokt Ultra hunting load, and a Metal Case military-type load. No varmint load is included. The four factory loads all have a muzzle velocity (MV) of 2800 fps and a muzzle energy (ME) of 2002 ft. lbs. from a 24" test barrel. At 100 yards the metal case bullet (BC .325) has a remaining velocity of 2523 fps and energy of 1625 ft. lbs. At 200 yards the velocity is 2262 fps and the energy 1307 ft. lbs. And at 300 yards the velocity is 2017 fps and the remaining energy 1039 ft. lbs. These figures are taken from Remington's 2004 catalog.
The trajectory of the metal case bullet looks like this: +1.2" at 50 yards, +2.7" at 100 yards, + 2.8" at 150 yards, +1.4" at 200 yards, -3" at 267 yards, and -6.6" at 300 yards. The maximum point blank range (+/- 3") is thus 267 yards. These figures are computed for a rifle with a telescopic sight mounted 1.5" over the bore. This, just like the Army claimed, is similar to the trajectory of the .308 with a 150 grain bullet.
The lighter weight .277" varmint and hunting bullets will presumably be the most popular choices in the 6.8mm SPC, and the latter are not thick on the ground. Suggested examples include the 90 grain Speer HP varmint bullet, 100 grain Barnes X-Bullet, 115 grain Sierra HPBT, 115 grain Remington Core-Lokt Ultra, and 120 grain Barnes X-Bullet.
Fast to medium burning rifle powders such as RL-7, IMR 4198, IMR 3031, IMR 4895, H4198, H322, H335, and Benchmark are indicated in the 6.8mm SPC. The MAP of the 6.8mm SPC appears to be about 55,000 PSI.
Here is some reloading data from the Hodgdon Powder Company:
Starting Load - 90 grain Speer HP bullet, 26.0 grains of H4198 powder, MV 2810 fps, 47,700 PSI.
Starting Load - 100 grain Barnes X-Bullet, 27.0 grains of H322 powder, MV 2502 fps, 37,700 PSI.
Starting Load - 115 grain Sierra HPBT bullet, 26.0 grains of H322 powder, MV 2421 fps, 43,500 PSI.
These loads were chronographed in a 24" test barrel using Remington cases and Remington 9 1/2 primers.
Note: A full length article about the 6.8mm SPC can be found on the Rifle Cartridge Page.
Copyright 2004, 2013 by Chuck Hawks. All rights reserved.