Struggling to keep up with the latest rifle cartridges? You’re not alone. With so many new introductions, it’s easy to get lost, especially if, like me, you’re not an avid hunter or long-range competitive shooter. And while I may not have tested the new “6.5mm Ultra-Blaster Super-Duper” cartridge, I can share my experience with a standout intermediate cartridge: the 6.8 SPC (Special Purpose Cartridge).

History of the 6.8 SPC Cartridge

Back in 2003, if you weren’t an AR enthusiast, you might have missed the buzz around the 6.8 SPC. Designed by two special forces and army marksmanship experts, this cartridge was built for battle and defense, aiming to surpass the 5.56 while fitting into the M4 carbine profile. Though not officially adopted by the Army, its real-world origins and superior performance make it a top choice for many.

Though not adopted as a replacement for the 5.56 as intended, the 6.8 SPC has made waves in the AR-15 community. Bill Wilson of Wilson Combat was one of its biggest advocates, producing top-notch AR-15s chambered in 6.8 SPC and using them for wild hog hunting. Other manufacturers followed suit, offering rifles and uppers in 6.8, and major ammo makers provided a variety of loads and bullet weights.

Why Choose 6.8 SPC?

The civilianized 6.8 rifles enhanced the M4 carbine’s effectiveness far beyond the original 5.56 chambering. The 6.8 SPC launches .270-caliber bullets weighing between 85 to 115 grains at velocities ranging from 3,012 to 2,800 feet per second, depending on load. In comparison, the 5.56mm sends .22-caliber bullets weighing 55 to 75 grains downrange at velocities ranging from 3,250 to 2,930 feet per second, depending on the load. The kinetic energy of the 75-grain 5.56 is 1,429 foot-pounds of energy, while the 85-grain 6.8 round delivers 1,642 foot-pounds of energy. The 115-grain 6.8 SPC rounds push this further, delivering 1,759 foot-pounds of energy. This significant difference in kinetic energy highlights the 6.8 SPC’s superior power and effectiveness.

After attending a law enforcement sniper school with a scoped 5.56mm AR-15, I sought an AR with more oomph but didn’t want a .308 bolt gun. I decided to try out the upper from a 6.8 SPC Stag Arms hunter that I was testing paired with a custom lower from Sun Devil. The 6.8 was a stellar performer as a law enforcement sniper rifle.

With just a bit more recoil than a 5.56, the 6.8 SPC delivers the perfect amount of power within the 64-to-100-yard range typical for police snipers. I qualified with and carried the 6.8 sniper setup along with the original M4 5.56mm upper, ready to swap out as needed.

During joint training with Columbus Police Department SWAT Snipers, the 6.8 SPC’s effectiveness was evident. Shooting at Lexan “bullet-resistant” glass blocks from 50 yards, the 6.8 SPC’s penetration and ballistic impact were impressive, rivaling that of the CPD’s .308. This reinforced my belief that the 6.8 SPC was ideal for my needs.

Further training at an abandoned concrete plant in Zanesville, Ohio, allowed me to test the 6.8 SPC out to 600 yards. Despite occurring years ago in 2007, I recall easily hitting the target, proving the 6.8 SPC to be a versatile and powerful round.

Rediscovering the 6.8 SPC

Between that testing in 2007 and now, the 6.8 SPC faded in popularity. Not only had the military failed to adopt it, for big game hunting, people seemed to prefer the more powerful 6mm and 6.5mm cartridges though they required a .308-framed AR.

I recently realized I still had plenty of 6.8 SPC and SPC II ammo left after leaving SWAT and decided to look into the availability of 6.8 SPC rifles and ammo. Several brands offer 6.8 SPC ammo, and there were plenty of 6.8 SPC AR-15 rifles and uppers though companies like Ruger dropped the cartridge from its lineup.

I needed a new 6.8 SPC upper or complete rifle in order to revisit the cartridge after a 13-year hiatus and turned to Rock River Arms (RRA). This company currently offers three 6.8 SPC II uppers and one complete rifle. The SPC II designation indicates an updated chamber and barrel twist rate that optimize velocity potential. I requested the SPC0592 Coyote Carbine Upper, a model set up for hunting that can also be used as a tactical upper for home and property defense from extended ranges.

Rock River Arms Coyote Carbine Upper Specifications

Caliber: 6.8 SPC II
Upper receiver: Forged A4
Barrel: 16-inch chrome moly / 1:10 twist
Muzzle: Smith Vortex flash hider / 5/8-24 thread
Gas block: Low profile
Handguard: RRA 12.5-inch lightweight free float rail / M-LOK compatible
Price: $720

Testing the 6.8 SPC Upper

The RRA 6.8 SPC complete upper halves work with RRA LAR-15 and other lower halves, requiring only a 6.8 SPC magazine for proper function. I mounted the RRA Coyote Carbine upper on my Sun Devil custom lower and added my Aimpoint Comp II Red Dot Sight atop. A magazine is not included with the RRA upper, so I purchased a 15-round aluminum magazine.

The RRA Coyote Upper is nicely set up with a charging handle that is easy to run with the left thumb and index finger off the left side. There is a full-length rail strip mounted atop the receiver and forend to accommodate as long an optic as you need. Its Smith Vortex is a three-prong Vietnam-styled flash hider used on the first M16s delivered to that combat zone. Each time you fire a shot there is a distinctive ring emitted from the “tuning fork” effect of the prongs.

I headed to the range with 20 rounds of Hornady 120-grain Super Shock Tip ammo (2,460 feet per second with 1,612 foot-pounds of energy) and set up a Springfield Armory Rifle Sight-In target at 25 meters, assuming a traditional cross-legged sitting position. The RRA upper ran smoothly, and the Aimpoint was dialed in perfectly for the 6.8 cartridge. My best group was 8-shots in 2 ¼ inches. The RRA upper balanced extremely well atop the lower and the fit was tight. With a proper high-magnification optic, this setup would dominate at distance.

The 6.8 SPC: Power, Precision and Versatility

The 6.8 SPC remains a highly versatile and valuable cartridge. Ideal for hunting hogs and deer-sized game, it also excels in home-defense scenarios. If you are looking for increased range and power without heavy recoil or expense, the 6.8 SPC is worth considering. There are still plenty of 6.8 SPC guns and ammunition available for modern shooters.

Rock River Arms: RockRiverArms.com
Hornady: Hornady.com