For over five decades, U.S. Army servicemen have relied on the 5.56x45mm and 7.62x51mm NATO cartridges. These are the next generation of the new "intermediate calibers” in between the 5.56mm and 7.62mm and offer ample power and flexibility to accomplish any military mission, as well to tackle most of the world’s medium game.
While these cartridges were developed primarily for the AR-15 and military M4 family of rifles, the aftermarket companies offer an abundance of weapon parts and accessories for the commercial market.
As experienced consumers, you probably already know that marketing campaigns and the real world are not equal, and the same holds true with ammo and guns. In short words, the 6.5 Grendel, 6.5 Creedmoor, and 6.8 SPC have gained popularity in the USA, but they are different in virtually every way.
Actually, the 6.8 SPC and 6.5 Grendel are very similar out to 300-400 yards., whereas the 6.5 Creedmoor is far better for reaching .300 Win mag distances.
In the following guide, you will find out why these fantastic cartridges allow the AR-15/10 rifles to perform far beyond what they were initially designed for.
What is a 6.5 Grendel (6.5x39mm)?
Launched in 2003 by Alexander Arms, a 6.5mm Grendel has been around for almost 15 years now. The Grendel is one of several intermediate cartridges chambered in the AR to maximize performance in the AR-15 platform with only basic modification to the weapon.
This intermediate cartridge is based on the Soviet`s military 7.62×39mm M43 design and competition 6.5mm PPC rounds. In fact, Alexander Arms put a 6.5mm bullet into a necked down 7.62×39 casing and developed a round with capabilities beyond the effective range of any 5.56mm NATO or .223 Remington hunting ammo.
The 6.5 Grendel is tailored to a new battlefield role called “the designated marksman” and represents a middle ground between the 5.56×45mm NATO and the 7.62×51mm NATO.
Since its introduction, the 6.5 Grendel has proved to be more accurate than its .223 counterpart, engaging targets at 500+ yards, as well as beyond the effective range of infantrymen equipped with standard AR-15/M16 rifles.
In terms of hunting, the Grendel makes the AR-15 a viable hunting rifle with ample choices of bullet weights which retain greater terminal energy at extended ranges compared to the 5.56 and 7.62.
Using a polymer-tipped and controlled-expansion, 6.5mm bullets up to 125 grains, the Grendel is best suited for the smaller species game, while Grendel ammo loaded with heavier 130 and 140 grain (8.4-9.0 g) bullets is perfect for longer range, tactical shooting.
What is a 6.5 Creedmoor (6.5x49mm)?
Introduced by Hornady and Creedmoor Sports in 2007, the 6.5 Creedmoor is another 6.5mm cartridge designed to replace the service caliber, but this time, the 7.62x51 NATO.
This 6.5mm cartridge is named after the most famous and oldest shooting competition in North America, the Creedmoor Match and, its decade-long presence 6.5 CM has garnered a reputation as a formidable round with better performance and significantly less wind drift than the current 7.62mm long-range cartridge.
Even though Creedmoor designation uses a 6.5mm caliber, its actual bullet diameter measures out to 6.72 mm (.264 inches). While the Creedmoor`s ballistics would suffer considerably when chambered in sporting rifles with typical 22" to 24" barrels, it will fully perform in auto-loading rifles with 28" barrels.
Created as a modification of the .30 Thompson Center (.30 TC), a 6.5 Creedmoor is offered with bullets weights ranging from about 90-160 grains (5.8-10.3 g), suitable for shooting everything from varmints to huge Scandinavian moose. The 6.5 Creedmoor is launching a standard load, 120-grain (8 g) A-Max bullet at a muzzle velocity of 3,020 ft./s (920 m/s) with a muzzle energy of 2,430 ft-lbs (3,290 J).
Hornady's new 6.5mm Creedmoor is an excellent round for long-distance shooting, as it duplicates the .300 Win. Mag’s trajectory with less recoil than a .308 Win. Providing performance essentially equal to the .260 Remington, the Creedmoor outperforms both the .308 Winchester and 7.62x54R at a distance. Even the US Military is considering switching over to a Creedmoor to fill the “range gap” between standard M16/M4 rifles, light machine guns, and precision, long-range sniper rifles.
Actually, in testing in 2017, the U.S. Special Operations Command has compared the 6.5mm Creedmoor and .260 Remington to the 7.62x51mm NATO cartridge, leading to the discovery that the 6.5mm versions of the firearms have 40 percent greater range and less recoil than their 7.62mm counterpart.
What is a 6.8 SPC (6.8x43mm)?
The 6.8 (6.8×43mm) Remington Special Purpose Cartridge (SPC) was developed in 2002 as part of the military’s Enhanced Rifle Cartridge program to create a cartridge specifically to address the perceived shortcomings of the 5.56mm.
The 6.8mm Remington SPC was designed to perform better in short barreled CQB rifles delivering 44% more energy than the 5.56 mm NATO from an M4 carbine at 100- 300 yards.
After dropping the 6.8 SPC in 2007 due lacking long-range effectiveness, the U.S. Army confirmed in 2017 they would adopt the new version of 6.8mm in Next Generation Squad Weapons (NGSW).
Designed specifically for military applications, and based upon a .30 Remington cartridge, the 6.8mm SPC cartridge is roughly mid-way between the M855 5.56mm and the 7.62mm NATO rounds, providing superior downrange lethality over the 5.56 NATO/.223 Remington with bullet trajectory close to the 7.62x51 NATO, but with about half the recoil.
The 6.8mm SPC cartridge is a 300 or 400-yard cartridge at best, while it gets the optimum balance of velocity at a bullet weight of around 100-120 grains. A typical 6.8x43 (6.8 SPC) cartridge with a 16" barrel launches a 110-grain bullet at 2,600 feet per second.
6.5 Grendel vs. 6.5 Creedmoor vs. 6.8 SPC
People are interested in comparisons and this article compares the 6.5 Grendel, the 6.5 Creedmoor, and the 6.8 SPC, the intermediate cartridges evaluated and tested by the U.S. and other militaries. Being a viable choice for the next-generation individual assault rifle/round combo, all of three types of ammunition have been around for quite some time and most of our enthusiasts already know the basic performance characteristics.
Along with half a dozen ammunition variants in "intermediate calibers," these three cartridges outperform the current 7.62mm and 5.56mm rounds nearly every time due to the lack of recoil and improved accuracy between 700 – 1,000 yards.
This quick-reference data sheet provides information for cartridge/bullet/velocity and energy combos, as well as recoil energy for all of three calibers.
Rifle Weight (lb.)
2,880 ft/s (880 m/s)
1,658 ft-lbs (2,248 J)
2,790 ft/s (850 m/s)
1,866 ft-lbs (2,530 J)
2,700 ft/s (820 m/s)
1,942 ft-lbs (2,633 J)
2,650 ft/s (810 m/s)
1,917 ft-lbs (2,599 J)
2,510 ft/s (770 m/s)
1,818 ft-lbs (2,465 J)
3,020 ft/s (920 m/s)
2,430 ft-lbs (3,290 J)
6.8mm Rem. SPC
2,710 ft/s (830 m/s)
2,283 ft-lbs (3,095 J)
6.8mm Rem. SPC
2,575 ft/s (785 m/s)
1,694 ft-lbs (2,297 J)
6.8mm Rem. SPC
2,460 ft/s (750 m/s)
1,612 ft-lbs (2,186 J)
6.8mm Rem. SPC
2,500 ft/s (760 m/s)
1,525 ft-lbs (2,068 J)
6.8mm Rem. SPC
3,070 ft/s (940 m/s)
1,780 ft-lbs (2,410 J)
The 6.5mm cartridges and 6.8 SPC can use bullets twice as heavy as the 5.56x45mm and make both rounds suitable for deer-sized big game.
On the other hand, these three calibers feature a similar range of bullets weights, but the 6.5 Creedmoor is far more aerodynamic than the other two. The longer and thinner bullets have better sectional density, meaning they retain speed better than light bullets due to the inertia. Unlike larger caliber bullets, the smaller, longer projectiles penetrate better due to decreased resistance.
The Grendel is currently commercially available in a large bullet weight assortment, making it an extremely flexible caliber appropriate for shooting varmints and small game or for more extended range, tactical shooting. The 6.5mm Grendel bullet ranges from the 90 grain (5.8 g), through the mid-weight 108-120 grain competition projectiles, and all the way to the full hunting weight projectiles of 130 and 140 grain (8.4-9.0 g).
While the 6.5 Creedmoor is ballistically superior to the 6.5mm Grendel and uses 6.8 SPC the Creedmoor 6.5mm bullets which span weights from about 85 to160 grains (5.5-10.3 g) in various styles. Practically, standard 6.5CM projectile weights run from 120 grains to 147 grains, keeping them suitable for shooting everything from small predators to Scandinavian moose.
The 6.8 SPC uses the same diameter bullet as the .270 Winchester but not of the same weight. Aside from the common use of 110 to 115 grain Sierra bullet, if you are looking at the spectrum of available 6.8 SPC commercial loads, you'll see offerings in the 85 to the 120-grain range at velocities of 3,070 to 2,460 feet per second. Even though the 6.8 and the 6.5 Grendel are designed for a very similar job, the 6.8 has a much larger selection of hunting bullets than the Grendel has to offer.
However, many other factors affect these rounds at the field or down range and we'll explain in the following chapters.
As a rule of thumb, lighter bullets have a flatter trajectory and are driven faster, with less recoil.
Besides those most apparent advantages, lighter loads have a few downsides, such as being more affected by wind and a faster loss of velocity in comparison to heavier weight bullets. In addition, faster bullets don't necessarily penetrate deeper, mainly in reference to expanding-type bullets.
The original Grendel concept includes long-range precision shooting and, to a lesser extent, hunting scenarios. Utilizing Nosler 120 grain ballistic tip hunting bullets, the 6.5 Grendel launches at 2,600 fps/1801 ft. lbs. muzzle velocity/energy, whereas it reaches 300 yards, twice as far as the vast majority of deer hunters require these days.
The initial 6.8mm Remington`s 115-grain bullet loading reaches a muzzle velocity of 2,575fps (785 m/s) and generates around 1,694 foot-pounds of energy (2,297 Joules). However, the new Barnes 85-gr TSX load runs over 3,000 ft./sec fired from 16" barrel, making it the fastest of all three rounds.
While the above-mentioned calibers are designed as AR-compatible cartridges, the 6.5 Creedmoor is the most powerful cartridge intended for bolt action rifles. Using slightly heavier bullets, it is in a different category than the other two. Being ideal for a distance and accuracy, a 6.5 Creedmoor should be great to, say 1,200 meters, give or take.
In comparison, the 6.5 Creedmoor factory-load Hornady's 143-grain ELD-X bullet attains a 2,700fps muzzle velocity (MV) and generates around 2,315 ft-lbs, making this hunting ammo capable of tackling anything from elk on down.
As for accuracy, the 6.5 and 6.8mm bullets are much more aerodynamic because the wider 7.62mm/308 projectiles have more drag (air resistance) than the compared slimmer bullets. These rounds are 30 percent less susceptible to wind drift, making it more precise at longer distances than their 5.56 and 7.62mm counterparts.
In short, the 6.8mm SPC handles a 300 or 400-yard cartridge at best, the Grendel is a 500 to the 800-yard round, whereas the 6.5 Creedmoor should be easily shooting out to around 1,200 yards.
Practicality: Platform Weight and Cost
Although developed to maximize performance in the AR-15 platform, the 6.8 SPC performs much better in shorter barrels, while the Grendel was designed to perform out of longer barrels. As already mentioned, the 6.5 Grendel and 6.8 SPC would be good choices if you're going on an AR-15 platform, since these buildings will only require a barrel, unique bolt carrier group, and the ammo.
Another selling point of the Grendel is its inexpensive ammunition, almost three times cheaper than 6.8 SPC or Creedmoore. While the converting an existing .223/5.56mm AR-15 to either cartridge is affordable and straightforward, the Jordanian Army and Saudi Royal Guard adopted the 6.8mm in 2010.
Being a versatile cartridge, the 6.5 Grendel can also be found in other firearms designs like the Kalashnikov system with Zastava Arms’ AK-based rifle developed for the Serbian Army.
On the other hand, the 6.5 Creedmoor is designed as a long-range target cartridge, duplicating the trajectory of the .300 win. magnum with significantly lower generated recoil.
As a newcomer among American hunters, it is a favorite caliber in bolt action rifles, but if you already have an AR-10 (.308) platform, all you need is a compatible 6.5mm Creedmoor upper.
A primary difference, in comparison to the 6.5mm Creedmoor, the 6.8 SPC and 6.5 Grendel cartridges were designed for two very different jobs. The 6.5mm Creedmoor was intended as a longer-range cartridge, while the Grendel and 6.8 were designed as a shorter-range cartridge that works well with AR-15 platforms and magazines.
The 6.5 Grendel and 6.8 Remington cartridges transform the AR into a hunting rifle, allowing it to effectively shoot modern bullet constructions at shorter to mid-ranges.
On the other side, designed for a large frame (AR-10/.308), the 6.5 Creedmoor is based on the .308 Win, making it potentially 300fps faster across the board than a 6.8mm or 6.5 Grendel.
All three cartridges are viable options for competitive target shooting or big game hunting, assuming the Creedmoor, big brother of the 6.8 SPC and Grendel, is capable of efficacy at longer distances.
Also, don't forget that both 6.5 Creedmoor and 6.5 Grendel are effective inside 20 to 22-inch barrels, whereas the 6.8 SPC is designed initially for firing out of 16" barrels.
In tests, it was determined that the Creedmoor has the shortest barrel life of 2,500 to 3,000 rounds. For target shooters and plinkers, it may be somewhat unattractive, but for the seasonal deer shooter, a 6.5 Creedmoor will endure for plenty of hunting trips.
Looking at the previous three cartridges, it is evident that Creedmoor has the largest case with a significantly greater volume. Recoil is a primary factor that affects accuracy, meaning that lower recoil makes shot placement easier
As one of the most critical factors affecting accuracy is the gun recoil, four main elements are to be considered in regards to recoil.
First of all, you should know that the gun recoil energy is measured in ft-lbs with the weight of the rifle, bullet weight and velocity, as well as the number of grains of powder, are directly used to determine the recoil felt to the shooter.
In the table above, you can discover that the 6.5 Creedmoor caliber, used on 308 platforms is much more potent than other two rounds designed for use on AR-15 weaponry. The Creedmoor has the most recoil out of those three but offers far less recoil than its .308 Winchester counterpart.
Platforms For the 6.5 Grendel
If you are using an AR platform available for the Grendel, the aftermarket offering is crowded with building accessories and parts of different quality and price, so be careful and well informed before making a decision.
Besides the barrel, the 6.5 Grendel uses a different bolt and different magazines when compared to a standard 5.56 NATO AR-15.One thing you should pay attention to is a difference between 6.5 Grendel Type I and Type II. There are two manufacturer specifications for the bolt and barrel chamber in reference to the difference in head spacing.
Type II is considered the original Grendel and is by far the most popular configuration, whereas the other maker, Les Baer Custom, has adjusted dimensions to his specific design. The most important detail is that you cannot mix and match parts for them without risk of damage.
The most important factors in constructing a bolt carrier group are the type of steel and heat treatment. The Brownells 6.5 Grendel BCG is built by combining the best choices of steel for the bolt and carrier. Actually, the bolt itself is machined from 9310 steel and the carrier is made of 8620 hardened steel. While 8620 steel is not recommended for bolts, it is mil-spec for the carrier, where it works perfectly.
After machining, each of these components has been shot-peened and completed with heat treatment to keep its strength over time. Instead of the mil-spec parkerizing, all parts of Brownells BCG are subjected to nitride treatment. While nitride-treated steel is exceptionally resistant to corrosion, it features a very smooth finish to reduce friction, which reduces the heat too.
This reasonably-priced, Type 2 bolt is caliber-specific and comes with bolt carrier and gas key, also featuring a firing pin, cam pin, and firing pin retaining pin.
Platforms for the 6.5 Creedmoor
Without a doubt, the 6.5 Creedmoor is an excellent cartridge growing rapidly in popularity and may eventually eclipse the popularity of the 7.62 NATO in the AR-10 platform. Since the 6.5 CM will get the best performance from longer barrels, keep in mind that you can't run a 16" barrel like a .308 Win.
A number of gun manufacturers have already added the 6.5 CM barrels to their catalogs because this cartridge often requires only a barrel replacement for the large-frame AR-10 rifles. Nowadays, a few rifle makers offer it as a standard choice on their guns.
Platforms for the 6.8 SPC
Designed to improve combat effectiveness in short-barreled (16.5-inch) M4 carbines, the 6.8 SPC cartridge launches heavier bullets than the standard U.S. 5.56 round.
Using the 6.8 SPC in a standard AR-platform, the rifle brings some benefits for AR owners, such as the fact that 6.8 SPC will work with a lot of common AR parts. Converting from a 5.56mm to the 6.8 SPC usually requires a bolt and magazine alteration, but the most straightforward and reliable modification would be swapping the magazine and complete upper receiver to make your 5.56 AR into a 6.8 SPC AR.
Without question, the 6.5 Grendel, 6.5 Creedmoor, and 6.8 SPC provide flat trajectory compared to service rounds, while delivering better lethality and downrange performance.
All three of these weapons have made considerable ventures into various civilian types of shooting, such as target and precision shooting disciplines or long-range hunting. However, as sportsmen, you should know that they are not ethical cartridges for long range hunting.
There's nothing honorable or admirable about injuring animals at long range just because you have a flat-shooting cartridge.