6.8 SPC vs 6.5 Grendel – A 2021 Guide

| Last Updated: June 8, 2021

Comparing ammunition is a tricky business but also a trend for gun reviewers these days.

When we say tricky, we mainly refer to cases of so-similar-but-at-the-same-time-so-different calibers such as the 6.5 Grendel and 6.8 Remington Special Purpose Cartridge (SPC).

Anyway, people like comparisons, and many can be found clashing the two said cartridges. We hope our review adds some value that we felt others left out.

TL;DR: 6.8 SPC vs 6.5 Grendel

There are still many proponents of big-bore around—those individuals who think that any caliber smaller than .30 is inadequate for combat.

In general, the 6.8 SPC is designed to offer superior downrange lethality over the 5.56mm in short-barreled rifles (SBR). The 6.5 Grendel on the other hand, has a similar goal but requires a minimum of 20 inches and a longer barrel for optimum performance.

The 6.8 SPC and 6.5 Grendel are roughly mid-way between the 5.56x45mm NATO and the 7.62x51mm NATO and they indeed come with some advantages and shortfalls.

Unlike several larger bore cartridges designed to function in AR-15 rifles, the 6.8 Remington SPC and the 6.5 Grendel deliver superior external ballistics to the 5.56 NATO in a package that shoots flatter, with a bit larger recoil and a slightly lesser magazine capacity.

6.8 SPC

6.5 Grendel

Pros

Pros

Very light recoil

Better bullet selection

Designed for short barrels

More affordable ammo

Slightly larger diameter bullet

Designed for longer barrels

Ideal for hunting small to medium-sized game

Longer practical effective range

Cons

Cons

Bullets with a lesser sectional density

About 25% more felt recoil

Not for precision long-range shooting

Smaller bullets weight assortment

3X the price of the 6.5 Grendel

Advantages diminish with shorter barrels

Best For

Best For

Self-defense and hunting at close to medium range

Competition and small game shooting

When Did the 6.8 SPC Come Around? 

Like many other small arms calibers, the 6.8 SPC was developed as part of the military program for enhanced cartridge to address the perceived shortcomings of the 5.56 NATO.

Rooted in the experiences from the Vietnam war era and other conflicts, the U.S. Army has started looking for the optimum military cartridge to create a one-caliber system. The new cartridge should have penetration capability of 7.62 NATO ball combined with the trajectory of the .300 Winchester Magnum and packed into a compact body not much bigger and heavier than the 5.56 NATO round.

After few “6mm Optimum” prototypes, the ideal military caliber has grown up to 6.5 (.264 caliber) and 6.8mm (.270 caliber). The 6.8 was designed to offer excellent performance out of a shorter barreled rifle providing 40% more power than the standard 5.56 M855 load the military used that time.

Officially released by Remington Arms Company in 2003, this .270 military cartridge or the 6.8x43 was purpose-built to be used in A.R. platform rifles with minimal modifications, including a slightly larger bolt, special magazine, and replacement of the barrel.

The 6.8 mm SPC cartridge originated from a shortened .30 Remington case, whereas it is using the same .277″ bullet diameter as the .270 Winchester, 270 WSM, or .270 Weatherby Magnum, among others. However, this very nice tiny cartridge generally uses lighter weight bullets than the cartridges mentioned above.

As the 6.8 SPC performs near its full potential with a shorter 16–18-inch barrel, it is a perfect cartridge for a short-barreled rifle (SBR).

Photo credit: thefirearmblog.com

When Did the 6.5 Grendel Come Around? 

Like the 6.8 SPC, the story of the 6.5 Grendel begins in the same place: with the .223 Remington and the AR-15.

Soon after introducing M16 and .223/ 5.56x45 as official caliber, western military thinkers were aware of 5.56 limited stopping power giving impetus to many entrepreneurs to develop a more powerful alternative to the .223 Remington.

Since .30 caliber is too much bullet, and .22 is too little, the logical next step would be to look at the .26 caliber as a middle solution between the 5.56x45mm NATO and the 7.62x51mm NATO.

The 6.5 Grendel was first unveiled in May 2003 by Alexander Arms, taking the AR-15 to a new level providing it the long-range capability of the M14. Due to its longer low-drag bullet, the 6.5 Grendel is more aerodynamic, offering much better ballistics than the 7.62 NATO round.

The 6.5mm Grendel is one of several intermediate cartridges explicitly designed for the AR-15 type of weapon.

Obviously, a 6.5 Grendel is a distant cousin of the legendary Kalashnikov 7.62x39 round, but its 39mm case is necked-up to accommodate standard .264" diameter bullets. You can find the same projectiles in the 6.5 PRC, 6.5 Creedmoor, and .260 Remington reputed cartridges for their long-range performance.

In terms of bullet drop and resistance to wind drift, 6.5 Grendel doesn't give a huge advantage at 300 yards, but beyond that, Grendel has a flatter trajectory, primarily when used in a rifle with a longer barrel.

While it shoots .264 bullets, Grendel's 123 gr delivers more energy than the larger diameter .277″ bullets used by the 6.8 SPC and has better armor penetration at 1,000 meters than the bigger and heavier 147 gr 7.62 NATO round.

Photo credit: lundestudio.com

Relevant Characteristics Between 6.8 SPC and 6.5 Grendel

Though both cartridges differ in relevant characteristics, a careful reader can find few valuable features that can help him make an informed decision appropriate for his shooting style and rifle applications.

Specs

6.8 SPC

6.5 Grendel

Barrel Matching

In less than 16-inch barreled firearms

Designed for 24″ and longer barrels

Bullet Selection

75 to 120-grain

90 to 140 grain

Bullet Diameter

.277" (6.8mm)

.264" (6.5mm)

Initial Velocity

2,850 fps

2,600 fps

Effective Range

300- or 400-yard cartridge at best

Effective from 200 to 800-yard

Maximum average pressure (MAP)

55,000 psi

50,000 psi

Similarities and Differences

Along with .300 Blackout, .450 Bushmaster, .458 SOCOM, and .50 Beowulf, designers were trying to develop larger bore cartridges for the AR-15.  In that context, the 6.8 Remington SPC and 6.5 Grendel are probably the most successful alternatives to the .223 Remington and 5.56x45mm NATO.

While both rounds are great for varmint hunting or target shooting, they differ in few things like parent cartridges, typical weapons configurations, and a practical, effective range.

6.8 SPC and 6.5 Grendel Differences 

Parent Cartridges

  • The 6.8 Remington SPC is an intermediate round developed from a vintage .30 Remington cartridge shortened at 2.260” and narrowed down to accept a .277-caliber (6.8mm) bullet.

  • The 6.5 Grendel cartridge is based on the 6.5 mm PPC case, which is, in fact, a variation of the .220 Russian case, a smaller brother of the 7.62 x 39mm (M43) Soviet military cartridge.

Barrel Matching

  • From the start, the new 6.8mm Remington Special Purpose Cartridge was designed to improve combat effectiveness and deliver excellent performance when used in shorter barreled (16.5-inch) M4 carbines.

  • The 6.5 Grendel, on the other hand, does indeed perform better at longer distances, but it was never intended to be shoot from barrels shorter than 20 inches. The Grendel is simply tailored for the designated marksman, a Soviet concept widely used by the U.S. military in Iraq and Afghanistan.

Bullet Diameter

  • Considering the bullet caliber, the 6.8 SPC is loaded with the larger diameter .277″ bullets, just like the .270 Winchester and 270 WSM.

  • On the other side, the 6.5 Grendel can accommodate standard .264" diameter bullets used by the 6.5 Creedmoor and .260 Remington.

Bullet Selection

  • Though it uses a slightly larger diameter bullet than the 6.5 Grendel (.0603 vs. .0547 square inches), due to the AR-15 magazine length constrictions, the 6.8 SPC ammunition can be loaded with bullets ranging from 75 to 120 grains.

  • The 6.5mm Grendel factory ammunition typically has bullet weights in the 90-130gr range, well-suited for target and varmint use.

Photo credit: abesguncave.com

Effective Range

  • With a bit more powder capacity, the 6.8 SPC generates a slightly higher pressure than the 6.5 Grendel resulting in higher initial velocities. 

  • That extra velocity also means that the 6.8 SPC has higher muzzle energy than the 6.5mm Grendel, making it a compact fast killing round for hunting varmints, whitetail deer, and tough feral hogs at ranges within 200 yards.

Recoil Energy

  • As for the recoil energy, the 6.8 SPC has a bit of an edge. It has about 25% less free recoil energy compared to 6.5 Grendel, making it a better option for the extremely sensitive.

6.8 SPC and 6.5 Grendel Similarities

  • Both cartridges are developed for the AR-15 and as a more aggressive stand-in for the .223 Remington/ 5.56x45mm NATO.

  • Because the AR-15 can only accommodate cartridges up to 2.26″ long, both rounds have the same overall length: 2.26″. It means they cannot accommodate heavier bullets for the caliber.

  • According to the original requirements, both cartridges can use unmodified STANAG 30-round 5.56 magazines, of course, with a smaller number of rounds.

  • Both cartridges have moderate kickback, which is still much milder than other similar performance cartridges.

  • Both rounds are significantly more powerful than the .223 Remington, making them perfect for personal defense or semi-automatic rifles.

  • The 6.5 Grendel and 6.8 Remington SPC cartridges have a comparable performance at normal hunting ranges, demonstrating the same lethality as the hunting grounds.

6.5 Grendel vs 6.8 SPC Ballistics Chart

While the trajectories and retained kinetic energy for both cartridges are similar at common hunting ranges, the 6.8 SPC shots larger diameter and more aerodynamic bullets than the 6.5 Grendel.

Until now, you are probably aware that the 6.5 Grendel can deliver its full potential and offer better performance out of an AR-15 than the 6.8 Remington SPC only when it is chambered in rifle barrels of 24 inches and longer.

On the other side, the 6.8 SPC maintains its efficiency and performance if you use a firearm shorter than a 16-barrel rifle.

Therefore, this ballistic table/chart should be viewed with a small grain of salt, given the different lengths of barrels.


6.5 Grendel 123gr from 24 in barrel

6.8 SPC 110gr from 16 in barrel

Muzzle Velocity

2,650 fps

2,650 fps

Muzzle Energy

1,917 ft-lb

1,525 ft-lb

100 Yds Trajectory

+2.2”

+2.2”

100 Yds Muzzle Energy

1,581 ft-lb

1,390 ft-lb

200 Yds Trajectory

-6.3”

-6.4”

200 Yds Muzzle Energy

1,213 ft-lb

1,120 ft-lb

500 Yds Trajectory

-52.8”

-83.3”

500 Yds Muzzle Energy

769 ft-lb

620 ft-lb

Source: Calguns.net

What About the .308?

It’s important to remember that the 6.8 Remington SPC and the 6.5 Grendel were developed to improve upon the .223 Remington stopping power. However, these two solid performers have also approached the highly respected powerhouse, the .308 Winchester, in certain aspects.

When comparing these two cartridges with .308 Winchester, it's like "apples to lemon" since there's a big gap in performance between the 7.62 NATO and 6.8SPC/6.5 Grendel.

Actually, both of these sub-.30 caliber cartridges were developed to offer superior downrange lethality over the 5.56 NATO/.223 Remington and bridge the gap between 5.56 mm and 7.62x51mm NATO.

Both the 6.5 Grendel and the 6.8 SPC have noticeably lighter recoil than the .308 Winchester/7.62x51mm NATO.

Photo credit: tacticalhuntr.com

As a middle ground between the M855 5.56mm and the 7.62x51mm NATO rounds, the 6.5 Grendel using a long barrel and heavy bullet offer better ballistics than the 7.62x51mm cartridge with 50% less felt recoil than 147gr 7.62 NATO M80 ball.

Utilizing a longer low-drag aerodynamic bullet, the 6.5 Grendel delivers better armor penetration at 1,000 yards than the bigger and heavier 147 gr (9.5 g) 7.62 NATO round.

While the Grendel 6.5mm provides the AR-15 with a long-range capability of the M14 and 7.62 NATO cartridge, the 6.8 SPC is lighter and has less recoil than the 7.62x51mm NATO cartridge. Although it is not the ballistic equal of the 7.62 NATO, the compact and mild recoil 6.8 mm SPC cartridge allows operators more controllable rapid-fire and enables them to carry more ammunition.

Bottom Line

Both of these cartridges can be considered as an upgrade over the 5.56 NATO/.223 Remington, initially designed for an M16/M4 pattern service rifle.

As it usually happens that civilians adopt military-style weapons and calibers, the 6.5 Grendel and the 6.8 SPC are soon accepted by shooters, hunters, and those who are seriously considering home security.

Both are outstanding hunting cartridges for deer, feral hogs, and varmints within a short to moderate distance.

While the Grendel 6.5mm was designed to be a longer-range cartridge, the 6.8 SPC was designed to be a shorter-range cartridge that worked well with a barrel shorter than 16 inches.

Both are very effective cartridges built to accomplish very different tasks.

He is a military historian enthusiast and hobbyist, war veteran and an avid hunter with more than 30 years of experience. He began reviewing firearms for publications in the mid -1990s and have been fortunate to make many friends in the industry. He has improved continuously his firearms skills and knowledge, which is a never ending journey.