6.8 SPC and 6.5 Grendel have been rivals since they hit the market. With so much in common, it’s no wonder that you may not be sure what is right for you.
From the history of the cartridge to the ballistics, we’ve got all the information that you need!
A Bit Of History
Ever since the .223/5.56 NATO cartridges were invented, people have been trying to replace them. Don’t get me wrong, 5.56 NATO is a great cartridge and it covers a lot of ground. There are a lot of bad guys in the world who aren’t with us anymore proving the effectiveness of that little round.
But even on its best days, 5.56 NATO is a bit lacking when it comes to raw energy.
There have been a dozen or more attempts to solve this with a new cartridge, but few have come close to succeeding. Two that came pretty close are 6.5 Grendel and 6.8 SPC.
I always enjoy talking about this cartridge because it lets me say that it was invented by Bill Alexander of Alexander Arms and it was named after the monster that attacks Beowulf’s mead hall in the poem Beowulf.
While the cartridge is awesome, the story gets a little… weird after that.
Normally, when a new cartridge is invented (and you actually want anyone to use it) you submit the specs to SAAMI (the industry organization that standardized ammo and chamber specs) for approval and standardization. Part of that process requires that you release any copyrights and trademarks to the ammo and chamber design.
Bill Alexander didn’t do that (at the time) and chose to keep his copyright on the 6.5 Grendel.
To get around this, Les Baer slightly modified the barrel and bolts they sold so that they were not the exact same as the Grendel specs.
And then for reasons that I honestly don’t understand, the Les Baer version started to be called “Type 1” while the Alexander Arms version was called “Type 2”.
This has led people to think that maybe Type 1 is the OG… it isn’t.
Eventually, Alexander Arms got their head on straight and submitted 6.5 Grendel to SAAMI for approval and in doing so released their trademarks/copyrights.
This is awesome for us shooters since the Type 2 Grendel is the better, stronger, version.
While there are still Type 1 bolts and barrels floating around out there, it’s really uncommon to come across one.
Bear Creek Arsenal exclusively uses the Type 2 6.5 Grendel barrels and bolts.
With an objectively less cool name, 6.8 Remington Special Purpose Cartridge has a decently cool backstory.
Designed by Remington with the help of the Army Marksmanship Unit and Special Operations Command (SOCOM), the 6.8 SPC was commissioned because of special operation units requested a cartridge that hit harder out of their M4 rifles than the standard 5.56 NATO was able to do.
Basically, high-speed tactical guys in units like Army Delta Force and the Navy SEALs needed something to give their M4s a bit of a boost in lethality.
Keep in mind that 5.56 NATO was really designed for 20” barrels. While the M4 uses a 14.5” barrel and barrels even shorter than that are not uncommon within SOCOM.
While cartridges like 300 Blackout and 7.62x39 work wonderfully from a short barrel, 5.56 NATO loses a lot of velocity and energy from such short lengths.
6.8 SPC was one answer to this problem.
Sadly, the development was rushed and there were pressure issues during military testing that basically killed the project.
While there aren’t official results, there have been anecdotal reports from guys that used 6.8 SPC uppers in the field during the GWOT that liked the cartridge.
While it might have failed to be adopted by the US Army, LWRCI continued development on the cartridge and on a special AR-15 to shoot it resulting in their Six8 line of rifles.
The Six8 was adopted by the Royal Guards of Jordan and Saudi Arabia, Sweden’s SOG (roughly equivalent to American Navy SEALs), the UK’s special forces, and by our own Pentagon Force Protection Agency.
Because of how extremely similar these two cartridges are, we’re going to talk about both at the same time since they cover the same ground.
Both 6.8 SPC and 6.5 Grendel are wonderful AR-15 hunting cartridges. They deliver 30-40% more energy than 5.56 NATO does in similar barrel lengths and can take deer-sized game out to 250-300 yards with ease.
Both cartridges also have widely available ammo designed for hunting and taking down game.
Long Range Shooting
While 6.8 SPC was primarily designed to improve the lethality of the M4 at close range, it performs very well out of a longer barrel and with more velocity.
6.5 Grendel is another awesome distance plinker that stays supersonic out to 1,000 yards with a 24”ish barrel.
Both are accurate, do well in the wind, and offer little recoil to help you stay on target and track your shots.
6.5 Grendel has better ammo options and generally a higher ballistic coefficient.
While both of these cartridges can be used inside the home, I really would not recommend it unless you have zero concern for overpenetration.
For most of us, with our pets, family, and even neighbors nearby both 6.5 Grendel and 6.8 SPC have too much potential for overpenetration for them to be good options in the home.
Both cartridges pack a punch at the muzzle even from short barrels, but both will sail through drywall.
If you live in a home that doesn’t have these concerns, both cartridges offer a major boost in energy on target without a major increase in recoil or handling.
Bottom line: 6.8 SPC and 6.5 Grendel perform almost identically given comparable barrel lengths and bullet design and bullet weight.
6.5 Grendel shooting Hornady 123gr SST from a 16” barrel flies at around 2,450 FPS.
6.8 SPC shooting Hornady 120gr SST from a 16” barrel flies at around 2,460 FPS.
At 16” these cartridges are neck and neck with each other. However, once you get shorter or longer things change slightly.
For a short barrel, let’s say 12”, 6.8 SPC starts to gain an advantage and sends that 120gr SST at around 2,380 FPS. 6.5 Grendel sends the 123gr SST from a 12” barrel at something around 2,250 FPS.
But on the other end, 6.5 Grendel tends to gain more velocity from longer barrels. Again, the 123gr SST out of a 24” barrel moves at around 2,580 FPS. 6.8 SPC sends a 120gr SST from a 24” barrel at just 2,520 FPS.
While 6.8 SPC performs “better” with short barrels and 6.5 Grendel performs “better” from long barrels, these differences are barely noticeable.
The biggest difference is when using a short barrel, if you want the most punch at closer ranges 6.8 SPC is a better choice. But honestly, I very much doubt that anything you shoot will go down to ~1500 ft.lbf when it wouldn’t go down to ~1,400 ft.lbf.
The real world biggest difference between these cartridges is basically that the market has decided that 6.5 Grendel is more popular.
For whatever reason, 6.8 SPC just never really caught on. And while it took 6.5 Grendel a minute, it has really taken off.
Maybe it’s because there is already a boatload of super popular 6.5mm cartridges and projectiles on the market, or maybe it’s because Grendel is a way cooler name than Special Purpose Cartridge.
Either way, the bottom line is that 6.5 Grendel has a LOT more variety in ammo choices.
From super cheap steel-cased plinking rounds to high-end match-grade long range precision rounds and every flavor of hunting bullet ever made, 6.5 Grendel has it.
You can even find it in stock at most local brick-and-mortar stores.
6.8 SPC has a fairly impressive selection of hunting rounds that are pretty easy to find in stock, but that’s about it. The low-end cheap ammo doesn’t exist for 6.8 SPC and the high-end match-grade ammo is really hard to find.
Prices between the two cartridges are fairly even if you’re looking at similar ammo, but 6.8 SPC tends to be slightly more expensive in general.
Build Or Buy
If you’re looking to build an AR-15 for either cartridge, you’re in luck because it’s super easy.
Both 6.5 Grendel and 6.8 SPC only require a new barrel, new bolt, and new magazines. They are not interchangeable with each other, but they are used for some other cartridges thus making them a bit more popular and easier to find.
Cartridges like 6mm ARC use the same bolt as 6.5 Grendel while .224 Valkyrie uses the same bolt as 6.8 SPC. So if you already have one or the other, you’re halfway home to making a new upper!
Make sure the barrel is made for the cartridge you want, the barrel and chambers are not interchangeable with any other cartridge.
If you’re looking to just buy a new upper… then do it! As with most things, AR-15, a new complete upper, and some new magazines and you’re god to go.
What Is Best For You
Maybe I’m a bit biased, but unless you’re just really interested in 6.8 SPC for some reason -- 6.5 Grendel wins in my mind.
6.8 SPC isn’t bad and it has some very respectable strengths, but for whatever reasons it simply hasn’t caught on like 6.5 Grendel has.
Both cartridges offer very comparable ballistics, both are wonderful platforms for reloading to really maximize what they can do, both have decent magazine and parts support.
But 6.5 Grendel has a lot more reloading and a lot more factory ammo options. Since 6.5 Grendel does 99% of what 6.8 SPC does, but has an order of magnitude more options to meet your needs, Grendel is just a better overall option.
Both of these cartridges are pretty awesome and both will serve you well. The biggest difference is simply that 6.5 Grendel is more popular and has more support. If you want to buck the trends, get a 6.8 SPC and have at it.
For ease of components, ammo, and rifles 6.5 Grendel wins hands down. Grendel also has a cooler name, so let’s face it -- that’s really what matters most.