Looking for a more powerful alternative to the .223 Remington for use in your AR-15? Here’s what you need to know about the 6.8 SPC vs 6.5 Grendel.
Most hunters and shooters would probably agree that Modern Sporting Rifles chambered in .223 Remington or 5.56x45mm NATO are great for varmint hunting, target shooting, and just having fun plinking at the range. However, using those smaller cartridges on larger game is a very controversial subject.
The AR-platform is extremely popular in the United States and offers many inherent advantages for hunters though.
For this reason, designers have made many attempts at building more powerful cartridges for the AR-15 over the years. Unfortunately, there are some significant challenges involved with building larger bore cartridges that improve upon the performance of the .223 Remington and 5.56x45mm NATO while still reliably functioning in an AR-15.
For that reason, hunters have two mainstream choices for medium bore AR cartridges: 6.5 Grendel and the 6.8 Remington SPC. Both cartridges are solid performers and there is quite a bit of overlap in their capabilities, but each also has different strengths and weaknesses.
In this article, I’m going to do a detailed comparison of the 6.8 SPC vs 6.5 Grendel and discuss the pros and cons of each one so you can make an informed decision regarding which cartridge will work best for you.
Before we get started, I have a couple of administrative notes:
First, the .223 Remington and the 5.56x45mm NATO are technically different cartridges, but the practical difference in performance between the .223 vs 5.56 doesn’t make any difference for the purposes of this article. Use extreme caution when attempting to interchange the .223 Remington with its NATO cousin though.
For a more detailed discussion on the differences between the .223 Remington and 5.56x45mm NATO cartridges, read this article:
Second, some of the links below are affiliate links. This means I will earn a small commission (at no extra cost to you) if you make a purchase. This helps support the blog and allows me to continue to create free content that’s useful to hunters like yourself. Thanks for your support.
Finally, I recorded an entire podcast episode on the various cartridge options for the AR-15 (to include the 6.8 SPC and 6.5 Grendel). If you’d rather listen than read, click the appropriate link below to listen to this episode on your preferred podcasting service.
6.5 Grendel & 6.8 SPC Podcast
History Of The 6.5 Grendel & 6.8 SPC
The story of each cartridge begins in the same place: with the .223 Remington and the AR-15.
The M-16 rifle and 5.56x45mm NATO cartridge got off to a pretty rough start in Vietnam with the U.S. Army and Marine Corps. While modifications to the rifle and ammunition solved most of the problems that plagued the system during the war, large numbers of people in the U.S. military still had very serious concerns regarding the stopping power of the diminutive cartridge.
These concerns were shared by civilian hunters who adopted the AR-15 and .223 Remington cartridge during the last couple decades of the 20th Century. While the rifle and cartridge worked extremely well for target shooting and predator/varmint hunting, the .223 Remington developed a reputation for poor performance on deer sized game.
However, the AR-15 platform offered a number of advantages to shooters and, not surprisingly, was also very popular in the United States.
Gun designers with their finger on the pulse of the American hunting and shooting communities realized that they were looking at a potentially massive opportunity.
Since so many people loved the AR-15, but the .223 Remington cartridge was not the best choice for hunting big game, designers set about developing a number of larger bore cartridges that were more powerful than the .223 Remington, but would still function in AR-15 rifles.
Among others, this list includes cartridges like the .300 Blackout, the .450 Bushmaster, the .458 SOCOM and the .50 Beowulf.
Bill Alexander (the same guy who developed the .50 Beowulf) designed the 6.5 Grendel to scratch this itch in 2002. By modifying a 6.5mm PPC case (itself descended from the .220 Russian and the 7.62x39mm cartridges), Alexander was very successful in building an efficient, accurate, and sweet shooting cartridge that functioned very well in the AR platform.
The 6.5 Grendel cartridge is also significantly more powerful than the .223 Remington. Not only that, but the cartridge is extremely versatile, so it functions well for long range shooting, varmint hunting, tactical, law enforcement, and big game hunting applications.
The cartridge did initially struggle to gain widespread acceptance in the shooting and hunting communities for a variety of reasons, one of which was the fact that Bill Alexander trademarked the name of cartridge. However, Alexander relinquished the trademark in 2011 when the cartridge gained SAAMI approval, thus allowing other companies to manufacture ammo, barrels, etc. bearing the name 6.5 Grendel.
Around the same time Alexander was building the 6.5 Grendel, the Remington Arms Company received a request from the United States Army Special Forces community to help them develop a more lethal alternative to the 5.56x45mm NATO cartridge that would still function in the M-4 carbine.
The new 6.8mm Remington Special Purpose Cartridge (also known as the 6.8 SPC) was the result of this development.
Basically, the folks at Remington in partnership with the Army Marksmanship Unit used a shortened .30 Remington case (cousin to the old .32 Remington and .35 Remington) necked down to shoot a 6.8mm (.270 caliber) bullet. The original goal was a 115 grain bullet at 2,800 feet per second (2,002 foot pounds of energy). However, the initial load offered to the public fired a 115 grain bullet at 2,625 feet per second (1,759 foot pounds of energy).
The 6.8 Remington SPC received SAAMI approval in 2004.
Just like with the 6.5 Grendel, the 6.8 SPC was considerably more powerful than the 5.56x45mm cartridge and had approximately 40% more muzzle energy than the standard M855 load the military used that the time.
In fact, that lethality advantage the 6.8 SPC had over the 5.56x45mm cartridge grew even more when both were compared using a shorter 16″ barrel.
Unfortunately, as was the case with many of the other cartridges Remington has designed over the years (like the 6mm Remington, .260 Remington, and .280 Remington), the company really botched the roll-out of the 6.8 SPC. In this case, initial 6.8 SPC rifles had a poor chamber design that led to pressure spikes with original factory loads, which resulted in Remington downloading the cartridge to keep pressures at safe levels.
Remington fixed those issues and shooters now have access to a 6.8 SPC II chamber with .050″ of additional freebore in the throat compared to the original SAAMI spec design.
However, this did not happen until after SAAMI approved the cartridge using the older specifications.
Now we have a situation where the SAAMI specifications of the 6.8 SPC still reflect the old chamber dimensions, so most of the 6.8 SPC factory ammo options are designed to be safe to shoot in rifles with the original 6.8 SPC dimensions.
Those factory loads are safe to use in rifles with either a SAAMI 6.8 SPC chamber or a 6.8 SPC II chamber, but the ballistic performance of that ammunition leaves something to be desired.
On the other hand, 6.8 SPC II chambers can safely handle hotter loads and handloaders that have a rifle with an 6.8 SPC II chamber can make some custom loads that more closely approach the full potential of the cartridge.
So, while the 6.8 SPC has a number of strengths, it’s easy to understand why that cartridge has also really struggled to gain widespread acceptance in the sporting community at large.
6.8 SPC vs 6.5 Grendel: Cartridge Sizes
As you can see in the photo below, the 6.5 Grendel and 6.8mm Remington SPC are similar in a few ways, there are some obvious differences between them as well.
First, the two cartridges have the same overall length: 2.26″. The AR-15 can only accommodate cartridges up to 2.26″ long, so both go right up to the limit that will fit in the rifle.
At 1.68″, the 6.8 Remington has a slightly longer case length than the 6.5 Grendel (1.52″).
Since they’re descended from different parent cartridges, the 6.8 SPC and 6.5 Grendel have different rim diameters: .422″ for the 6.8 SPC and .438″ for the 6.5 Grendel.
For these reasons, case capacity for the two cartridges is similar, but the 6.8 SPC usually has a tiny bit more powder capacity than the 6.5 Grendel.
Each cartridge also uses different diameter bullets: .264″ for the Grendel and .277″ for the SPC.
Most 6.5 Grendel ammo typically has bullet weights in the 90-130gr range, with 100gr, 110gr 120gr, and 123gr bullets being the most popular. The 6.8 SPC ammo normally uses 75-120gr bullets, with 85gr, 110gr, 115gr, and 120gr bullets being the most common.
The 6.8 SPC is also loaded to a slightly higher pressure than the 6.5 Grendel (55,000psi vs 52,000psi).
6.5 Grendel vs 6.8 SPC Ballistics
Those differences in the external dimensions of the 6.5 Grendel and 6.8 SPC translate into some interesting differences in their ballistic performance.
This is illustrated in the table below comparing Hornady factory ammunition. The 6.5 Grendel load uses a 123gr ELD-M (.506 BC) while the 6.8 SPC load uses a 120gr SST (.400 BC).
Note that Hornady advertises a velocity of 2,580fps for this particular 6.5 Grendel load, but uses a 24″ barrel to do so. At the same time, they advertise a velocity of 2,460fps for their 6.8 SPC load with a 16″ barrel. In the interest of conducting as close to an “apples to apples” comparison as possible, I also included ballistic data for that same Hornady 6.5 Grendel load with a velocity of 2,369fps from a 16″ barrel.
All three loads used a 100 yard zero.
As you can see, the 6.5 Grendel load using a 24″ barrel starts off with about a 12% edge in kinetic energy that increases with range (about 40% more at 500 yards). This is due to the fact that this particular load uses a heavier bullet with a higher ballistic coefficient and a faster muzzle velocity.
Additionally, that particular 6.5 Grendel load has a flatter trajectory at all ranges. Like with kinetic energy, this advantage grows as range increases: it has about 1″ less bullet drop at 200 yards, about 3″ less at 300 yards, about 7.5″ less at 400 yards, and almost 15″ less bullet drop at 500 yards.
However, things change quite a bit when the 6.5 Grendel is used in a shorter barreled rifle.
In that case, the 6.8 SPC actually starts off with about 5% more kinetic energy. The 6.5 Grendel is still using a heavier and more aerodynamic bullet though, so that slight advantage in kinetic energy decreases and eventually flips in favor of the 6.5 Grendel between 100 and 200 yards. At 500 yards, the 6.5 Grendel has about 15% more kinetic energy.
When fired from a 16″ barrel, the 6.5 Grendel also has almost exactly the same trajectory as the 6.8 SPC.
All that being said, the gap in performance between the cartridges is pretty minimal at ranges inside 200 yards.
The chart below compares how much a 10 mile per hour crosswind impacts those same 6.5 Grendel and 6.8 SPC loads out to 500 yards.
Once again we see that the 6.5 Grendel outperforms the 6.8 SPC in terms of wind drift at longer range. This holds true for both barrel lengths, though the gap in performance is smaller when the 6.5 Grendel is fired from a shorter barrel.
However, the 6.8 SPC is still a very effective cartridge at short to moderate range.
The table below compares the recoil produced by very similar loads to the ones compared above for each cartridge when fired from identical rifles.
Felt recoil will vary from shooter to shooter and rifle to rifle, but free recoil energy is still a useful way to compare cartridges.
As you can see, both cartridges have very mild recoil, but the 6.8 SPC has the edge in this area. Specifically, the 6.8 SPC has about 25% less free recoil energy than the 6.5 Grendel. That’s really saying something because the 6.5 Grendel is also known for having a very mild recoil itself.
So where do we stand with each cartridge?
6.8 SPC vs 6.5 Grendel
The 6.5 Grendel shoots smaller diameter and generally more aerodynamic bullets than the 6.8 SPC. Trajectories and retained kinetic energy are similar at typical hunting ranges when both cartridges are fired from the same length barrel. The 6.5 Grendel has a slight advantage when used in longer barrels.
The 6.5 Grendel is a moderately powerful, relatively flat shooting cartridge that’s also pretty resistant to wind drift. This is especially remarkable considering that the cartridge packs that level of performance into a very small package that can still fit in the relatively tight constraints of the AR-15 platform.
Though it does have more recoil than the 6.8 SPC, the 6.5 Grendel recoil is still noticeably lighter than other mild recoiling cartridges like the 6.5 Creedmoor and the .308 Winchester, so most shooters and hunters can handle it without any trouble at all.
Additionally, the 6.5 Grendel also has an advantage when it comes to bullet selection. Since it utilizes .264″/6.5mm bullets, there is a better selection of high BC bullets for the 6.5 Grendel that are well suited for long range performance than is the case for the 6.8SPC.
Don’t think I’m dogging on the 6.8mm SPC though.
Make no mistake: it’s a very good hunting cartridge with outstanding terminal performance.
While the 6.8 SPC does give up a certain amount of performance to the 6.5 Grendel in terms of ballistics, this is especially pronounced at longer distances. You should also note that it’s possible to get a little bit better performance with handloads in a 6.8 SPC II chamber, so the gap in performance between the 6.8 SPC vs 6.5 Grendel does narrow a bit under those circumstances.
The same goes for barrel length.
Remember: the situation changes quite a bit when comparing the performance of those cartridges from rifles with the same barrel length.
The 6.5 Grendel has a definite advantage when comparing performance of loads fired from a 6.8 SPC rifle with a 16″ barrel vs a 6.5 Grendel with a 24″ barrel.
However, while the 6.8 SPC still offers very good performance out of a shorter barreled rifle, the Grendel’s performance edge vanishes when that 100-200 fps velocity advantage diminishes or is lost completely when fired out of a short barrels.
The 6.8 SPC round is more than powerful enough for hunting varmints as well as medium sized game like feral hogs and deer at short to moderate range and still delivers great performance when used in shorter barreled rifles.
It also uses a slightly larger diameter bullet.
Specifically, the larger diameter .277″ bullets used by the 6.8 SPC have about 10% more frontal surface area (also known as cross sectional area) than the 6.5 Grendel (.0603 vs .0547 square inches). All other things being equal, a bigger bullet will make a bigger hole, cause more tissue damage, and result in more blood loss.
All things considered, it’s an outstanding hunting cartridge.
Glenn and Michelle Guess (who have taken literally thousands of hogs) really like using the 6.8 SPC for hog hunting, particularly at night with a thermal scope. Watch the video below to see just how effective the cartridge is on a couple of really big, tough boars.
In addition to hunting, the 6.8 SPC is also a great choice for self defense/personal protection for people who like the AR-15 platform.
What about 6.5 Grendel vs 6.8 SPC accuracy?
On one hand, the 6.5 Grendel has seen extensive use in the hands of competition shooters and has an outstanding reputation in that area.
The 6.8 SPC is capable of excellent accuracy as well.
However, the aforementioned advantages the 6.5 Grendel has in terms of bullet drop and resistance to wind drift make the Grendel a much better cartridge for long distance shots past 300 yards, especially when used in a rifle with a longer barrel.
In any case, both cartridges are absolutely capable of tack driving accuracy in the right hands.
6.5 Grendel vs 6.8 SPC Ammo
Since both the 6.8 SPC and the 6.5 Grendel are intended for a specific niche in the hunting community, neither is extremely popular in absolute terms. That said, there are some good factory ammo choices for both cartridges.
Most notably, this list includes Federal with their Fusion MSR and American Eagle lines and Hornady with their American Gunner, Black, and Custom lines.
Alexander Arms still produces 6.5 Grendel ammo and Wolf also offers a pretty good low priced full metal jacket (FMJ) option for the cartridge. Nosler used to sell 6.5 Grendel ammunition as well, but they have discontinued production of 6.5 Grendel ammo at this instant though.
Nosler produces 6.8 SPC ammo via Silver State Armory (SSA). Prvi Partizan, Remington, and Sellier & Bellot also offer a couple of different 6.8 SPC ammunition options as well.
Since both cartridges are used by a relatively small segment of the hunting world, not every sporting goods store keeps 6.5 Grendel or 6.8 SPC ammo in stock. The 6.5 Grendel is usually a little bit more common out of the two though.
Availability of ammunition is usually pretty good online and the bigger retailers typically have a good selection of quality factory ammo for both cartridges in stock.
If you’d like to learn more about some of the various hunting ammunition choices for the 6.5 Grendel, read this article:
Fortunately, reloading components for both cartridges are widely available.
The 6.8 SPC is somewhat noteworthy for using the same .277″ bullet diameter as the .270 Winchester, .270 Weatherby Magnum, and 270 WSM. That said, the 6.8 SPC generally uses lighter weight bullets than those other cartridges, so there is a somewhat limited selection of suitable .277 caliber bullets for the 6.8 SPC.
Among others, the Barnes TSX, TTSX, and TAC-TX, Hornady GMX, InterBond, InterLock, SST, and V-Max, the Nosler AccuBond, Ballistic Tip, and E-Tip, and Partition are options for reloading the 6.8 SPC.
Bullets like the Barnes LRX, TSX, TTSX, and TAC-X, the Hornady ELD-X, GMX, InterBond, InterLock, SST, and V-Max, the Nosler AccuBond, AccuBond Long Range, Ballistic Tip, E-Tip, and Partition, the Remington Core Lokt, and the Swift Scirocco and A-Frame (just to name a few) are options for reloading the 6.5 Grendel.
6.5 Grendel vs 6.8 SPC Rifles
Once again, the 6.5 Grendel is a little bit more widely available and there are a couple of good semi-automatic as well as bolt-action rifles chambered in that cartridge. On the other hand, there are only a handful of options for firearms chambered in 6.8 SPC
Alexander Arms manufactured the first rifles in 6.5 Grendel and continues to do so. Since then, Wilson Combat and a couple of other companies like Radical Firearms and Brenton USA have started producing modern sporting rifles chambered in the cartridge. It’s also possible to purchase a 6.5 Grendel upper receiver and convert an existing AR-15 to shoot the Grendel.
The Ruger American Ranch and Predator bolt action rifles are currently manufactured in 6.5 Grendel. The same goes for the CZ 527 and the Howa Mini.
On the other hand, options are more limited for 6.8 SPC rifles. At this instant, Barrett, Rock River, and Savage all produce semi-automatic 6.8 SPC rifles. Like with the 6.5 Grendel, it’s possible to purchase a 6.8 SPC upper receiver (like one from LWRC) and convert an AR-15 to shoot the cartridge.
I’m not aware of any current production bolt-action 6.8 SPC rifles, but the Remington 700 and Ruger Hawkeye were both available in the cartridge at one point and turn up in the secondary market from time to time.
6.8 SPC vs 6.5 Grendel Magazines
We can’t have a 6.5 Grendel vs 6.8 SPC comparison without discussing the magazine situation for each cartridge.
The 6.5 Grendel and the 6.8 SPC can use regular M16 rifle/M4 carbine magazines with a slight drop in magazine capacity. A typical 30 round magazine will hold 25 6.8 SPC rounds and 26 6.5 Grendel rounds.
That said, it’s sometimes necessary to modify the feed lips, spring, and/or the follower of a typical AR-15 magazine for optimum reliability with these bigger bore cartridges.
In fact, magazines may be the single biggest cause of feeding problems with the 6.8 SPC and 6.5 Grendel.
Fortunately, this is a simple and relatively inexpensive problem to solve.
ASC and Duramag both make good quality 6.8 SPC magazines with capacities ranging from 5 all the way up to 28 rounds.
Both brands are available below.
Things are similar for the 6.5 Grendel.
However, the use of purpose built 6.5 Grendel magazines seems even more important with this cartridge since it has a larger rim diameter and significantly different shape compared to the 223/5.56 (and 6.8 SPC) cartridges.
For this reason, purpose built 6.5 Grendel magazines with a modified follower and feed lips provide optimal reliability. That said, Duramag and ASC are both still good options for quality 6.5 Grendel magazines with excellent reputations (both are available below).
6.8 SPC vs 6.5 Grendel: Which Is Right For You?
Do you primarily hunt medium sized game like deer, feral hogs, or black bear at ranges within 200 yards? Both cartridges will absolutely get the job done if you do your part and there isn’t a gigantic difference between them ballistically inside of 300 yards.
Are you looking for a the better cartridge for long range hunting for game like mule deer or pronghorn in open country where you might need to take a shot at several hundred yards? The 6.5 Grendel has a flatter trajectory, will drift less in the wind, and carries significantly more energy out past 200 yards.
Do you prefer to use a semi-automatic rifle for hunting or for personal defense? Both will work very well in this role. There are more 6.5 Grendel ammo and rifle options, but the 6.8 SPC is still a nice choice.
Are you looking for the perfect cartridge to use in a short barreled rifle (SBR)? Go with the 6.8 SPC. It performs near its full potential with a shorter 16-18 inch barrel and loses minimal velocity with even shorter barrels. This is in contrast to the 6.5 Grendel which requires a 20 inch or longer barrel for best performance.
Are you sensitive to recoil and in need of a serious low recoil cartridge? Both have very light recoil, but the 6.8 SPC has noticeably less than the 6.5 Grendel.
Do you want the round that is best suited for target shooting out past 400 yards or so in a precision rifle? Again, go with the 6.5 Grendel and use a longer 20″ or 24″ barrel. Especially with longer barrel lengths, the cartridge has a longer practical effective range and really stands head and shoulders above the 6.8 SPC for precision long range shooting.
The 6.5 Grendel and the 6.8 SPC are both solid rifle cartridges. However, the differences between them (6.8 SPC vs 6.5 Grendel) are pretty big in many respects. Carefully evaluate your needs as a hunter based upon the circumstances you foresee using the cartridge in, get a good hunting rifle chambered in the cartridge you select, learn to shoot it well, use quality bullets, and it should serve you well afield.
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The Lyman 50th Edition (p181-182, 195-196) and Hornady 10th Edition (p301-304, 348-350) reloading manuals were used as references for the history of the cartridges. The data used to compare the trajectory of the cartridges was obtained from Hornady (here and here). Data used to calculate recoil was obtained from the Hornady 10th Edition reloading manual. Case capacities were obtained from Chucks Hawks and LoadData.com. Maximum pressure obtained from SAAMI (p23). I used ShootersCalculator.com to compare trajectory and recoil for the cartridges.
John McAdams is a proficient blogger, experienced shooter, and long time hunter who has pursued big game in 8 different countries on 3 separate continents. John graduated from the United States Military Academy at West Point and is a veteran of combat tours with the US Army in Iraq & Afghanistan. In addition to founding and writing for The Big Game Hunting Blog, John has written for outdoor publications like Bear Hunting Magazine, The Texas State Rifle Association newsletter, Texas Wildlife Magazine, & Wide Open Spaces. Learn more about John here, read some of John’s most popular articles, and be sure to subscribe to his show: the Big Game Hunting Podcast.