6.5 Grendel vs 5.56 NATO

So, you’re in search of a new AR but can’t decide between the standard 5.56 NATO or the specialized 6.5 Grendel? While they are both popular chamberings for the AR-15, the 5.56 NATO and the 6.5 Grendel are very different cartridges with different capabilities. In this article, we will be going over some of these differences to help make your decision a little easier.

Physical Attributes

Stood side by side, it’s not hard to see that the 5.56 NATO and the 6.5 Grendel are entirely different cartridges overall. In fact, the only similarities shared by these cartridges are their maximum overall length of 2.26 inches and that they both use small rifle primers (in most cases). Now that we have the similarities out of the way let’s go over the many differences.

Looking at the bullets of each cartridge, you will probably notice the difference in diameter. The 5.56 is a 22-caliber cartridge that uses 0.224-inch diameter projectiles. Bullets of this diameter typically weigh between 35 to 95 grains, though most 5.56 offerings use bullets weighing between 55 to 77 grains. The 6.5 Grendel, on the other hand, is a 26-caliber cartridge that uses 0.264-inch diameter projectiles. This is nearly an 18 percent increase in diameter over the 5.56, which allows for much heavier bullets. In fact, 0.264-inch projectiles typically range from 90 grains up to 160 grains, though factory-loaded 6.5 Grendel offerings rarely go over 130 grains.

To accommodate for these heavier projectiles, you will notice the large difference in case length between each. Coming in at a length of 1.760 inches, the 5.56 case towers over the 6.5 Grendel’s case length of 1.52 inches. Though shorter, the 6.5 Grendel’s case length allows for longer and heavier projectiles to be seated within the same overall length as the 5.56. In fact, both cartridges share the same maximum overall length of 2.26 inches, even though their case lengths are significantly different. This maximum overall length ensures that both cartridges will function within the dimension tolerances of standard-length AR-15 magazines.

You may notice, however, that although they share the same maximum overall length, the 6.5 Grendel and the 5.56 do not share the same width. With a diameter of 0.441 inches, the 6.5 Grendel’s rim is about 16.4 percent larger than the 5.56’s rim diameter of 0.378 inches. So, although the 6.5 Grendel’s case is shorter than the 5.56, its wider body gives it a distinct advantage when it comes to powder capacity. In fact, the 6.5 Grendel has an H2O capacity of approximately* 35 grains. Compared to the 5.56’s approximate* H2O capacity of 28.5 grains, this is an increase of 22.8 percent. This massive increase in powder capacity is the primary reason behind the 6.5 Grendel’s increase in muzzle energy over the 5.56. It should be noted, however, that the 6.5 Grendel does not have as high of a magazine capacity as the 5.56 (in the same profile) due to this extra width.

Power

While the 5.56 is somewhat of a speed demon, it leaves a lot to be desired when it comes to muzzle energy. With a standard 55-grain projectile, the 5.56 produces approximately 1,282 ft/lbs. at a muzzle velocity of 3,240 feet per second. Although this muzzle energy figure is nothing to scoff at, it pales in comparison to the 6.5 Grendel. Hornady's 123-grain 6.5 Grendel offering is listed at a muzzle velocity of 2,580 feet per second and a muzzle energy of 1,818 ft/lbs. These figures make for a 41.8 percent increase in muzzle energy over the 5.56 load referenced above, which is substantial (especially in hunting scenarios).

It should be noted, however, that 5.56-load offerings containing heavier projectiles often produce more muzzle energy than standard 55-grain offerings. In fact, Hornady’s 75-grain JHP Frontier offering in 5.56 produces 1,410 ft/lbs. at a muzzle velocity of 2,910 feet per second. Although this is a 10 percent decrease in velocity compared to the 55-grain offering, it is a 10 percent increase in muzzle energy. Although closer, 1,410 ft/lbs. of muzzle energy produced by the 5.56 does not come anywhere near the 1,818 ft/lbs. of muzzle energy produced by the 6.5 Grendel. So, if you’re in search of power, the 6.5 Grendel is the obvious winner.  

Range

As you can see, the 6.5 Grendel produces substantially more muzzle energy than the 5.56, but it’s also going considerably slower. So, how do the 2 cartridges compare in terms of range?

To gather this information, we must first find the ballistic coefficients of the bullets being used in each cartridge. With Hornady’s Frontier load in 5.56, we see its 75-grain JHP bullet has a G1 ballistic coefficient of 0.355. With Hornady’s Black load in 6.5 Grendel, we see its 123-grain ELD-M bullet has a much higher G1 ballistic coefficient of 0.506.

With a much higher ballistic coefficient, the 6.5 Grendel carries substantially more energy down range than the 5.56. In fact, at approximately 180 yards, the 6.5 Grendel is carrying as much kinetic energy as the 5.56 produces at the muzzle. That performance is impressive, though it does have its drawbacks. Because of its relatively slow muzzle velocity, the 6.5 Grendel suffers from more drop when compared to the 5.56. With the loads referenced, the 6.5 Grendel has more drop than the 5.56 until they reach the 1,075-yard mark (approximately) where the 6.5 Grendel begins to drop less. Past this range, however, the effectiveness of the 6.5 Grendel begins to dwindle as it only remains supersonic to the 1,100-yard mark. It should be noted that this is 22.2 percent longer than the 5.56’s supersonic range of 900 yards, so the 6.5 Grendel is a better choice for longer-range shots (at least with factory loads).

Price

When it comes to price, these cartridges are in completely different leagues. Although the 6.5 Grendel is a somewhat popular chambering for the AR-15, it is nowhere near the popularity of the 5.56. In fact, the 5.56 is currently one of the most popular centerfire rifle cartridges in both the military and commercial markets, which helps to drive its prices down. The 6.5 Grendel, on the other hand, is somewhat of a niche cartridge that has only gained a fraction of the following of the 5.56. Because of this, pricing is often double (sometimes even more) that of the 5.56, often resembling the price of 308 Winchester or even 6.5 Creedmoor ammo.

When we move into reloading, it would be easy to assume that the prices would become similar. However, this is not typically the case. Although the 5.56 and 6.5 Grendel use the same primers and have somewhat similar powder charges, 0.264-inch bullets are usually noticeably more expensive than their 0.224-inch counterparts. On top of this, 6.5 Grendel brass is usually more expensive and harder to find than 5.56, which factors into its higher loading costs.

Because of this, the 6.5 Grendel is considerably more expensive to shoot, regardless of the method you use to acquire ammo.

Which One Should You Get?

There is no denying that the 5.56 and the 6.5 Grendel are very different cartridges with very different capabilities. Perhaps the biggest difference between them is their popularity. The 5.56 is currently one of the most popular centerfire rifle cartridges in existence, which helps to lower costs and create a wide assortment of factory options. Although the 6.5 Grendel is nowhere near the popularity of the 5.56, it offers considerably more power at any range. Compared to factory-loaded 5.56 offerings, the 6.5 Grendel uses bullets with much higher ballistic coefficients that help make it a superior long-range option. Realize that this performance comes at a cost, however, as prices are often double that of the 5.56.

Perhaps the biggest question to ask yourself is if you are really going to take full advantage of the 6.5 Grendel’s potential at longer ranges. If the answer is no, the 5.56 is still a very capable cartridge at a much more affordable price. Regardless of which one you decide, hopefully, this article helps make your decision a little easier.

*The case capacities listed represent the approximate amount of H2O that will fit inside an empty case. These values can vary based on the manufacturer, as different companies will typically result in slightly different case capacities.

--Banana Ballistics