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The 6.5mm Grendel and 6.8mm Remington SPC were inspired independently while seeking terminal knockdown surpassing .223 Remington/5.56mm NATO performance within the wildly popular AR-15. Both cartridges are very successful, providing ballistic performance dead center of the .223  Remington/5.56mm NATO in AR-15 and .308 Winchester/7.62mm NATO in AR-10 rifles. Converting an existing .223/5.56mm AR-15 to either cartridge involves swapping barrels, bolts and magazines or simply exchanging complete uppers.

These two cartridges were developed in 2002. The gun world has been arguing the relative merits of these  groundbreaking cartridges ever since. It seems gun loonies can’t talk about one without mentioning the other. Naturally, as gun nuts are wont to do, the Ford-versus-Chevy-style debates often become heated. Both cartridges have inspired dedicated websites.

Nevertheless, is one significantly better than the other? Let’s unpack the details for an objective look into the answer.

For test rifles, the author used an Alexander Arms AWS in 6.5 Grendel (top) and custom-built AR-
15 in 6.8 Remington SPC (bottom). Both cartridges demonstrated excellent accuracy potential using factory ammo.

6.5 GRENDEL

The 6.5 Grendel is the brainchild of Bill Alexander—former British Ministry of Defense contractor and current Alexander Arms owner—while “looking for something with more legs; something you could hunt whitetails with.” With assistance from competition shooter Arne Brennan and Lapua engineer Janne Pohjoispaa, the cartridge gained traction and was unveiled at the North Carolina Blackwater Training Facility in 2003.

The Grendel proved ballistically superior to the .223/5.56mm and .308/7.62mm NATO at longer ranges due to superior ballistic coefficients. For instance, the Grendel demonstrates better armor penetration with 123-grain bullets at 1,000 meters than the 7.62mm NATO with 147 grains and remains supersonic past 1,200 yards. Since its unveiling, the Grendel has provided benchrest accuracy, extreme efficiency and hunting versatility from 200 to 800 yards—ranges far beyond those previously gained from AR platforms. The Grendel drew from the 6mm PPC case developed by Dr. Lou Palmisano and Ferris Pindell in the 1970s for benchrest shooting. It retains an AR-15-compatible 2.260-inch OAL, includes a .439-inch head diameter, the 30-degree shoulder is moved forward to increase powder capacity, and cases are necked to accept .264-caliber bullets. The Grendel holds small rifle primers, and neck/shoulder areas are thickened to improve durability during semiauto cycling.

“The 6.5mm Grendel and 6.8mm Remington SPC were inspired independently while seeking terminal
knockdown surpassing .223 Remington/5.56mm NATO performance within the wildly popular AR-15.”

The Grendel has evolved into one of the most versatile, commercially available cartridges chambered in the AR-15 platform. It handles light bullets for varmints/predators and heavier pills for deer and hogs through a 1:9- to 1:7.5-inch rifling twist. The Grendel isn’t finicky; it provides low extreme velocity spreads of 10 to 25 fps. It propels 90-grain bullets to 2,900 fps and 130-grain pills to 2,500 fps while exhibiting 50 percent less recoil than 7.62mm NATO M80 ball ammo. As a rule, the Grendel sacrifices about 10 fps for every grain of bullet weight added.

The tightest group assembled while shooting 6.5 Grendel factory ammunition was printed with Alexander Arm’s 123-grain Lapua Scenar bullets. The five-shot, 100-yard group measured .41 inch and was shot in breezy winter conditions.

Early on, the Grendel remained a trademark cartridge, limiting availability to Alexander Arms rifles and ammo. In 2010, Hornady Manufacturing Company obtained licensing to produce ammunition, brass and dies. Alexander released its trademark in 2011, and the Grendel was adopted by the Sporting Arms & Ammo Manufacturing Institute (SAMMI) in 2012.

“The Grendel has evolved into one of the most versatile, commercially-available cartridges chambered in the AR-15 platform.”

6.8 REMINGTON SPC

The 6.8 Remington SPC (special-purpose cartridge) was created specifically for military applications. It was developed by Remington in collaboration with members of the 5th Special Forces Group, U.S. Army Special  Operations Command. The goal was to improve on 5.56mm NATO lethality from the M4 carbine (16-inch barrel) in response to reports that 5.56mm rounds had proven unreliable at incapacitating enemy combatants in the field—while also providing minimal magazine capacity loss and nominal recoil increases. The 6.8mm caliber was chosen to split the difference between 6.5mm accuracy and 7mm terminal performance. It was originally planned to propel 115-grain bullets at 2,800 fps with 2,002 foot-pounds of energy; those numbers were adjusted to 2,625 fps/1,759 foot-pounds before SAAMI approval in 2004. By that time, 6.8s were performing in the field against enemy combatants during special operations.

Cases with both large and small rifle primers are encountered—for example, Remington cases holding large rifle, Hornady and SSA cases small rifle. The 6.8 SPC is based on the .30 Remington and produces about 44 percent more energy than the 5.56mm at 100 to 300 meters. It was specifically designed for efficiency in short barrels, so increasing barrel length beyond 16 inches provides only nominal velocity gains.

“At the muzzle, the 6.8 SPC is faster and has more energy than the Grendel. At average 50- to 200-yard hunting ranges, big-game animals will notice zero difference. “

By 2007, U.S. SOCOM and the Marine Corps decided not to field the 6.8mm, because its comparatively short bullets lacked long-range effectiveness. Nonetheless, the Jordanian Army adopted the 6.8mm in 2010, and the Saudi Royal Guard ordered 6.8s in LWRC Six8 rifles soon after. You’ll encounter 6.8mm rifles with rifling twists from 1:9.5 to 1:12, with 1:11 most common.

TO EACH ITS OWN

I’ve shot 6.5 Grendel and 6.8 Remington SPC ARs extensively. Each delivers on initial objectives, yet each remains unique. Neither cartridge does its best work with heavier .264-/.277-caliber bullets, because rears intrude into powder space. The 6.5 Grendel strikes an optimum balance at 100 to 123 grains, with the 6.8 SPC around 115 grains. Both hold 25 rounds in 5.56mm/30-round-length magazines. And both are relatively slow to heat barrels. Pitted head to head (with the Grendel shooting 123-grain and the SPC shooting 120-grain Hornady SST bullets. Refer to the ballistics sidebar on page 32), the Grendel leaves the blocks at 2,350 fps and the SPC at 2,460 fps, with the former producing 1,508 foot-pounds of energy to the latter’s 1,612.

The 6.5 Grendel factory ammunition tested here includes loads from
many makers (left to right): American Eagle Varmint & Predator
90-grain TNT; Alexander Arms (AA) with Nosler 120-grain Ballistic Tip;
AA with Barnes 120-grain TSX; Federal Fusion MSR 120-grain SP;
American Eagle 120-grain Open Tip Match; Hornady Custom 123-grain
SST; AA with Lapua 123-grain Scenar; Hornady Black 123-grain ELD
Match; Hornady Custom 129-grain SST; Federal Premium Gold Metal
with 130-grain Berger Match; and AA with 130-grain Swift Scirocco.

At the muzzle, the 6.8 SPC is faster and has more energy than the Grendel. At average 50- to 200-yard hunting ranges, big-game animals will notice zero difference. Past 250 yards, the Grendel, via higher BCs, steps ahead slightly, posting slightly higher velocities  and slightly less bullet drop and wind drift. By 500 yards, the Grendel takes a decisive lead, outpacing the 6.8 SPC by 100 fps and losing 6 fewer inches to drift in 10 mph crosswinds. By 750 yards—and especially 1,000—the 6.5 Grendel leaves the 6.8 SPC in the rearview in all ways that matter.
The Grendel typically gains 20 fps for every inch of barrel added. The SPC, as mentioned, gains minimal velocity as barrel length is increased. The Grendel is the better long-range cartridge, offering reliable accuracy at 500 to 750-plus yards. The 6.8 offers more-lethal terminal impact at closer ranges but remains, at best, a 300- to 400-yard round.

The 6.5 Grendel—chambered in an Alexander Arms AWS—proved capable of excellent accuracy, assembling five five-shot groups of under an inch at 100 yards on a breezy winter day.

I detect no noteworthy difference in cost per round, but the SPC seems to be the more popular cartridge—based solely on availability of factory ammunition. I found 16 6.5 Grendel loads from five manufacturers, versus 24 6.8 SPC loads from seven makers. Grendel loads range from 90 to 130 grains. The lightest bullets loaded in 6.8 factory ammo are 85- to 90-grain pills, with 110- to 115-grain bullets representing the majority and a 120-grain bullet the heaviest bullet currently loaded for the 6.8. (See sidebar).

This was once a proprietary cartridge loaded only by Alexander Arms. Since its trademark was released, the cartridge has become quite popular and is loaded by a wide variety of manufacturers in an assortment of bullet weights.

IN THE FIELD

My only field experience with 6.5 Grendel and 6.8 Remington SPC rifles involve dark nights and thermal imaging scopes. If you’ve employed thermal imaging technology, you understand paper sight-in is tricky, at best—providing little indication of a rifle’s inherent accuracy. As a result, I temporarily set the thermal imagers aside and mounted matching Pentax GameSeeker 4-12x40mm scopes to print groups using factory rounds (the sidebar on page 33 includes the performance results).

A custom-built AR-15 in 6.8 Remington SPC proved its accuracy potential while shooting
several brands and makes of factory ammunition, posting four five-shot, 100-yard groups that
printed under an inch in breezy winter conditions.

Thermal imaging entered the equation because a friend from West Texas was experiencing hog depredation on his deer-hunting properties. We thinned the less-educated hogs with .223 ARs during daylight hours, but this had the same effect as the old joke about sending 1,000 politicians to the bottom of the sea: Hogs, especially pressured hogs, are vampire-ish by nature.  Nighttime hunting offered a solution. While .223s—fed hand-loaded, controlled-expansion bullets—proved adequate during daylight hours, darkness added new dimensions. For starters, nighttime hands-and-knees tracking through thick Texas underbrush doesn’t fit into a healthy lifestyle approach! We needed additional knockdown but preferred ARs for multi-target scenarios and accompanying Picatinny rails for attaching handy gadgets such as weapon lights/lasers. The Grendel and SPC provided the wallop while maximizing handling ease and minimizing the shoulder abuse baked into AR-10s.

While test-firing 6.8 Remington SPC rounds for accuracy with factory ammunition,
the author ran 14 different loads. Each one proved more than accurate enough for hunting applications, while four loads printed under an inch in five-shot, 100-yard groups.

My initial experience with Alexander’s AWS 6.5 Grendel is illustrative. I’d slipped within 90 yards of a mixed herd during black night. The Grendel was loaded with 129-grain Hornady SST loads that Alexander offers. I found the largest boar through the Trijicon IR-Hunter and touched off. He rolled over, anchored, while his cohorts headed for the exits. I swung on another big boar, shooting behind him by feet (noted via the bullet-friction heat signature), pushing to his nose and rolling him like a head-shot rabbit. I heard grunting approaching from behind, so I spun in time to see a string of sizeable hogs bearing down and only feet away. I shot into the ground in front of them, turning them on a more useful trajectory. I allowed them some ground while swinging with the largest hog’s nose. I squeezed and watched another dust-boiling wipeout. None of those hogs so much as kicked after impact. The largest weighed more than 350 pounds.

The Federal Premium Fusion MSR is a great hunting load. It performed well in the 6.5 Grendel and was the best performer in the 6.8 SPC.

Performance proved similar with a custom-build 6.8 SPC that delivered 120-grain SST Hornady Custom rounds. So, is one round superior to the other? That depends largely on your goals and the conditions at hand: long-range accuracy versus close-range brute force. For average shooters—whether these rounds are used for home defense or hunting—shooting at average ranges, there isn’t a nickel’s worth of difference. The 6.5 Grendel and 6.8 Remington SPC both remain revolutionary cartridges.

During group testing, the author ran many 6.8 Remington SPC brands and loads through the paces. With the author’s rifle, the best five-shot, 100-yard group resulted from Federal Fusion MSR 115-grain softpoint—a cluster measuring .42 inch.

BALLISTICS CHART

Range

(yards)

Drop

(inches)

Velocity

(fps)

Energy

(ft-lbs)

Wind Drift

(inches)

6.5

6.8 6.5 6.8 6.5 6.8 6.5

6.8

0

-2.6

-2.6 2,350 2,460 1,508 1,612 N/A N/A
250

-10.1

-9.4 1,959 1,955 1,048 1,018 5.4

6.6

500

-75.0

-74.4 1,613 1,524 710 619 23.6

29.5

750

-225 -235 1,324 1,196 479 381 58.0

74.2

1000 -299 -548 1,116 1,008 340 271 111 142

NOTES: The 6.5 Grendel shot Hornady SST 123-grain bullets; the 6.8 Remington SPC shot Hornady SST 120-grain bullets. Velocity was an average of five shots measured using a ProChrony at 10 feet in front of the muzzle.

An AR-15, whether in 6.5 Grendel or 6.8 SPC, makes an ideal platform for nighttime hog-shooting pursuits. Picatinny rails not only allow the addition of deadly thermal imaging scopes, they also allow for weapon lights (to avoid cactus and rattlers), as well as lasers for point-blank finishing shots.

AMMUNITION PERFORMANCE RESULTS

6.5 GRENDEL (Alexander Arms AWS, 20-inch/barrel rifling: 1:9 twist)

Velocity (fps)

Group Size (inches)

American Eagle 90-grain TNT JHP

3,023

0.85

Federal Fusion MSR 120-grain

2,615

1.07

American Eagle 120-grain Open Tip Match

2,618

0.60

Alexander Arms 120-grain Nosler Ballistic Tip

2,526

0.49

Alexander Arms 120-grain Barnes TSX

2,550

0.89

Hornady Black 123-grain Hornady ELD-M

2,593

0.63
Hornady Custom 123-grain Hornady SST

2,580

0.52
Alexander Arms 123-grain Lapua Scenar*

2,565

0.41

Alexander Arms 130-grain Hornady SST

2,391

0.56

Alexander Arms 130-grain Swift Scirocco

2,352

1.38

Federal Premium Gold Metal Berger 130-grain OTM

2,398

0.74

*Best group with this rifle

 

6.8 REMINGTON SPC

(SAA upper, 16.5-inch BHW/barrel rifling: 1:11 twist)

Velocity (fps)

Group Size (inches)

SSA by Nosler 85-grain E-Tip

2,941

1.43
American Eagle 90-grain TNT JHP

2,983

0.47
SSA by Nosler 90-grain BSB

2,839

0.88

Federal Fusion MSR 90-grain MSR

2,869

0.94

Hornady Full Boar 100-grain GMX

2,551

1.79

SSA by Nosler 100-grain AccuBond

2,695

0.60

Hornady American Gunner 110-grain BTHP

2,574

1.14

Hornady Black 100-grain V-Max

2,489

1.25

SSA by Nosler 115-grain Custom Competition

2,590

0.76
Remington 115-grain OTM

2,663

1.15
SSA by Nosler 115-grain Spitzer

2,721

0.90

Federal Fusion MSR 115-grain*

2,459

0.42

American Eagle 115-grain FMJ

2,463

1.40

Hornady Custom 120-grain SST

2,447

1.42

*Best group with this rifle


NOTES: Group sizes where five shots and were measured at 100 yards. 

 

CONTACT INFORMATION


ALEXANDER ARMS

DOUBLETAP AMMO

FEDERAL PREMIUM AMMUNITION

HORNADY MANUFACTURING COMPANY

PENTAX SPORT OPTICS/RICOH IMAGING AMERICAS CORP.

PPU/PRVI PARTIZAN

REMINGTON AMMUNITION

SELLIER & BELLOT

SSA BY NOSLER INC.

TRIJICON, INC.

Editor’s note: A version of this article first appeared in the August 2018 print issue of Gun World Magazine.