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Why might a hunter be contemplating 6.5 Grendel vs 308 Winchester? The two cartridges, after all, are very different, essentially representing two separate power levels. Well, the most obvious reason for the 308 Winchester vs 6.5 Grendel debate is if a hunter cannot decide between a conventional bolt-action rifle or an AR-15. Sure, both cartridges can be had in bolt- and semi-automatic rifles, but from a hunting standpoint, both also represent a best, or near best, general-purpose option in each platform. Here’s how the 6.5 Grendel and 308 stack up head-to-head.

6.5 Grendel vs 308 Winchester: Basic Ballistic Comparison

We’ll get into the finer details of how these two cartridges compare from an external and terminal ballistics standpoint, but if you just want a snapshot, here it is. As you can see from the chart below, the cartridges have similar muzzle velocity, but the 308 carries significantly more energy from the start. Trajectory, too, is all but identical out to 400 yards. But again, if you’re looking for enough energy to do damage at that distance, the 308 has the clear edge.

Chart showing a ballistics comparison of the 6.5 Grendel vs 308 Winchester
Richard Mann

The 308 Winchester

Now, let’s step back and look at each cartridge individually. This 308 Winchester has a military heritage, and like all American military cartridges, it is very popular. Winchester introduced it in the 1950s and it has grown in popularity ever since. It will easily match the original ballistics of the 30-06 Springfield cartridge, do it with a shorter case, and do it in rifles with a shorter action. It gained fame with military and police snipers and is unquestionably one of, if not the best, general-purpose rifle cartridges currently available. All of this is why Jeff Cooper selected the 308 Winchester for his concept general-purpose rifle known as the Scout Rifle.

Two boxes of 308 Winchester ammo, plus three loose cartridges on a white background
The 308 Winchester is one of the most versatile of all centerfire rifle cartridges for big game hunting. Richard Mann

The Sporting Arms and Ammunition Manufactures Institute (SAAMI) originally specified a 1 in 12 twist rate for 308 Winchester rifles, but with the advent of longer and heavier bullets with higher ballistic coefficients, most modern 308 Winchester rifles have the faster 1 in 10 twist to stabilize these projectiles. It used to be that any time a new rifle was introduced, its first chambering was the 30-06. That’s not the case anymore; the 308 Winchester has now eclipsed the 30-06 in popularity. Using bullet weights ranging in from 130- to 180-grains, I’ve killed more big-game animals with the 308 Winchester than any other cartridge. It’s as integral to American culture as mustard is to a hot dog.

The 6.5 Grendel

Two boxes of 6.5 Grendel ammo, plus several loose cartridges on a white background
The 6.5 Grendel is one of the best AR15 compatible cartridges for big game hunting and long range shooting. Richard Mann

Designed from the 7.62×39/220 Russian cartridge case, the 6.5 Grendel was intended to be a low recoiling but ballistically efficient rifle cartridge for the AR-15. The Grendel languished with mostly a cult-like following from its conception in 2003 until it was legitimized by SAAMI about seven years later. Since major firearms and ammunition manufactures will not build guns and ammo for non-SAAMI approved cartridges, it wasn’t until about a dozen years ago that the 6.5 Grendel really found its legs and a solid following with hunters and shooters.

Today the 6.5 Grendel is not just a popular cartridge in the AR-15, it has found a home in a variety of bolt-action rifles. In both platforms, it has a lot of appeal because of its combination of a good ballistic performance and low recoil. Though the 6.5 Grendel is slightly ballistically inferior to the 6mm ARC cartridge, it is one of the best big-game cartridges for the AR-15. Many hunters prefer it to the 6mm ARC due to the more ammunition options and the heavier bullets that are available. It is also popular for whacking steel at extended range and there are about a dozen, quality, factory loads to choose from, with bullet weights ranging from 90 to 123 grains.

6.5 Grendnel vs 308: External and Terminal Ballistics

One of the primary considerations with external ballistics is trajectory. Velocity and energy matter, but together they are more of a terminal ballistics concern. Trajectory determines how much you will have to adjust your sights to get a hit as the distance to the target increases. Surprisingly, with most loads, the 308 Winchester and the 6.5 Grendel are nearly identical out to reasonable hunting ranges of say 400 yards. This surprises many hunters, especially since out of the same weight rifle, the 308 Winchester recoils with more than twice the force. That extra force comes from heavier bullets and more gunpowder. Where you really see the advantages of the 308 Winchester as a hunting cartridge is in terminal ballistics. Let’s take another look at the ballistics chart, again.

Chart showing a ballistics comparison of the 6.5 Grendel vs 308 Winchester
Richard Mann

With terminal ballistics the story is a different, at least in terms of energy. At the muzzle, the 308 Winchester will have about a 40 percent advantage in kinetic energy. But as the distance increases, things start to level out. Except for extreme examples, velocities with both cartridges will fall below 2000 fps somewhere between roughly 375 and 425 yards. This means that depending on the bullet used, bullet upset/expansion starts to become iffy past that distance. Of course, there’s a bit more at play here.

The amount of bullet upsets determines wounding and tissue destruction, and that, combined with bullet weight, influences penetration. This is where the 308 Winchester has the clear advantage. Generally, the 308 Winchester will penetrate about 20 to 40 percent deeper than the 6.5 Grendel, and the bullet will upset with a frontal diameter that’s about 10 to 30 larger. This is substantial, generally, but for not for some specific hunting situations. The 6.5 Grendel will usually push bullets to between 18 and 26 inches of penetration, with bullet upset of about 1.6 times original diameter. Both cartridges, therefore, are more than sufficient for any deer at sensible distance.

6.5 Grednel vs 308: Recoil

The author shoots a bolt-action rifle chambered in 308 Winchester for a bench rest.
No matter how tough you think you are, less recoil usually means better precision. Richard Mann

Macho-man hunters act like recoil is a non-existent thing and not apt to admit that might affect their shooting. But it almost certainly does. It does not matter how much of a tough guy you are, harder kicking rifles are more difficult to shoot with consistent precision, period. Now, the 308 Winchester is not generally thought of as a hard-kicking rifle, but it’s a non-disputable fact that the 6.5 Grendel recoils with about half the force of the 308. Given that both cartridges have similar trajectories, if you’re only shooting paper and steel—or deer-size game at reasonaly ranges—the lighter recoil of the 6.5 Grendel has a lot of appeal.

Rifle Compatibility

A Howa Carbon Stalker bolt-action rifle on a white background, available in 6.5 Grendel and 308
The Howa Carbon Stalker bolt-action rifle weighs 6 pounds, 5 ounces in 308 Win and just 4 pounds, 14 ounces in 6.5 Grendel. Howa

Unless you’re intending to hunt larger species of big game like elk and moose, rifle compatibility might be the most important consideration between these two cartridges. If you’re looking at bolt-action rifles, a conventional 308 Winchester rifle can weigh a half pound more than some bolt-action rifles built on a mini action for the 6.5 Grendel. This is even more exaggerated with semi-automatic AR-styled rifles. For example, the Stag Arms Stag 15 Pursuit in 6.5 Grendel weighs a full 10 ounces less than the company’s Stag 10 Pursuit in 308 Winchester. With other AR-10 and AR-15 comparisons the weight differential can be even more. The bottom line is that you can find a lightweight rifle chamber for either cartridge, but the Grendel is apt to be lighter.

6.5 Grendel vs 308: Picking a Winner

As mentioned, these cartridges occupy different power levels. The 308 Winchester will produce muzzle energies between 2000 and 3000 foot-pounds, and the 6.5 Grendel is a sub-2000 foot-pound cartridge. For hunters, this means that at least from a ballistics standpoint, the 308 Winchester is better equipped to handle larger game. Since the trajectories of both cartridges are similar, for the recreational shooter, the 6.5 Grendel has a tremendous advantage due to its much lighter recoil and compatibility with lighter-weight rifles. Ammunition for the 6.5 Grendel also costs a bit less. In the end, the 6.5 Grendel vs 308 boils down to this: A deer hunter cannot go wrong with either, an elk hunter should probably opt for the 308, and for fun in the sun, go with the Grendel.