6.5 Grendel vs. 300 Blackout: Which One Is Better?

The 6.5 Grendel and 300 Blackout were designed to outperform the 5.56 NATO in the AR-15 platform.

The former is loaded with a 6.5mm (.264 caliber) projectile; the latter, a .30 caliber bullet.

As you continue reading, you’ll discover how the differences in these cartridges’ dimensions and projectiles affect their performance in the real world. We’ll judge each cartridge based on recoil, trajectory, accuracy, cost, and a few other crucial performance factors.

Cartridge Specs

At first glance, the cartridges’ physical specifications differ only slightly. You’ll notice that the 300 BLK has a wider bullet diameter than the 6.5 Grendel (0.308 inches vs. 0.264 inches). This allows the 300 Blackout to fire heavier bullets, albeit at the cost of lower muzzle velocities. Bullet weights for the 300 Blackout typically range from 110 to 220 grains, whereas 6.5 Grendel bullets conventionally weigh 80 to 144 grains.

The 6.5 Grendel has a larger base diameter than the 300 AAC Blackout (0.439 inches vs. 0.376 inches). Its larger case reduces magazine capacity and limits the number of rounds a soldier can carry onto the battlefield – one reason why it didn’t take off among national militaries.

6.5 Grendel vs. 300 Blackout Recoil

The 6.5 Grendel has about 6 ft-lbs of free recoil energy (noting that the figure varies substantially depending on ammunition specs and firearm weight). The 300 Blackout has about 4 ft-lbs of free recoil energy. While some shooters might notice a slight difference, these cartridges’ recoil is quite similar.

The 300 BLK has a slight edge, as it typically has less recoil – especially when it is loaded with lightweight projectiles.

The 300 Blackout wins this first section. But can it hold on to its lead?

Trajectory

Trajectory quantifies a bullet’s flight path to its target, measured in inches of bullet drop. A flatter trajectory is preferred because it requires the shooter to make fewer adjustments in pursuit of accuracy.

This is where the real differences begin to appear. The 300 BLK was designed for close-quarters combat (CQB), so a flat, long-range trajectory was never mandatory for the cartridge. When sighted in at 100 yards, a 125 grain bullet with a muzzle velocity of 2,250 fps will exhibit -7.0 inches of drop at 200 yards, and -54.8 inches drop at 400 yards.

While the 6.5 Grendel’s trajectory can’t compete with the 6.5 Creedmoor’s in terms of flatness, it’s still much better than the 300 BLK. When zeroed in at 100 yards, a 123 grain bullet with a muzzle velocity of 2,580 fps will exhibit -4.5 inches of drop at 200 yards, and -35.3 inches drop at 400 yards.

The 6.5 Grendel ties it back up by having the much flatter trajectory.

Accuracy: 300 Blackout vs. 6.5 Grendel

Accuracy is tricky to analyze, as several factors contributing to it cannot be measured objectively. Rifle design, barrel life, ammo consistency, shooter skill, and environmental conditions all influence accuracy.

Recoil also affects accuracy, especially when firing over longer ranges. Many shooters report being more accurate with a rifle that has less recoil. This is because the shooter can focus more on the fundamentals of shooting (e.g. breath control, trigger squeeze, not disturbing sight alignment) rather than worrying about how badly recoil is going to hurt.

These two rounds’ recoil isn’t different enough to significantly impact accuracy in this comparison. Most shooters would struggle to tell the difference. Therefore, we defer to the cartridge with the flatter trajectory.

The 6.5 Grendel will be more accurate, especially at longer ranges (200+ yards).

Ballistic Coefficient

The ballistic coefficient (BC) of a bullet measures how efficiently it stabs through the air. In other words, BC is a numeric representation of how aerodynamic a bullet is. A higher BC is preferred, as the bullet will conserve more momentum, resist wind drift more effectively, exhibit a flatter trajectory, and strike its target with greater energy (relative to a bullet of the same weight, diameter and velocity).

Generally, a longer, heavier bullet has a higher BC than a stubbier, lighter one.

Some heavier subsonic 300 Blackout bullets have an extremely high BC, such as the 208 grain Hornady A-MAX (G1 0.648). Exceptions like those aside, most 300 BLK ammo generally has a G1 BC between 0.267 and 0.393.

The 6.5 Grendel usually has a G1 BC between 0.205 and 0.510. For reference, a match-grade 123 grain Hornady SST has a G1 BC of 0.510.

Thanks to its heavier projectiles, the 300 BLK can have a higher BC. But when comparing bullets of similar weights, the 6.5 Grendel has the edge, making this section a tie.

Stopping Power: 6.5 Grendel vs. 300 BLK

“Stopping power” can deceive you into presuming one cartridge is intrinsically more effective than another for defense and/or hunting. While things like energy transfer, penetration depth, and bullet design do matter, shot placement counts the most.

To be sure: A poorly placed shot with a more powerful cartridge is less effective than a well-placed shot with a less powerful one.

With that out of the way, which of these two rounds has more stopping power? The 6.5 Grendel transfers more kinetic energy to its target despite utilizing slightly narrower bullets. For that reason alone, 6.5 Grendel wins this section.

Hunting

Neither of these cartridges was designed as a hunting round, but both have found success in hunters’ hands.

6.5 Grendel vs. 300 Blackout for Deer

The 300 BLK reminds me of the 30-30. It’s suitable for close-range whitetail deer hunting, but it just doesn’t hold up well for shots over 200 yards. For shots longer than 200 yards and under 800 yards, the 6.5 Grendel is the better deer hunting cartridge.

6.5 Grendel vs. 300 Blackout for Hogs

Whether you’re looking to take down hogs, varmints, or deer, the 6.5 Grendel is the better option, as it has a longer effective range (up to 800 yards compared to 300 yards for the 300 BLK) than the 300 AAC Blackout and packs a little more punch.

The 6.5 Grendel wins this section thanks to its flatter trajectory and harder punch. Simply put, it lets you kill deer from farther away.

Home Defense: 6.5 Grendel vs. 300 AAC Blackout

I’m not a fan of using a rifle for home defense. Rifle cartridges are more likely to over-penetrate and endanger your family and neighbors. But that doesn’t mean you shouldn’t use one if that’s all you have available to you. While I prefer using a shotgun or pistol for home defense, a rifle is better than nothing – especially when it’s chambered for either of these cartridges.

The 6.5 Grendel and 300 BLK are great because they’re both designed for the AR-15 platform: an easily customizable semi-automatic rifle.

However, the 300 BLK is the better option for a few reasons. First, it was designed for close-quarters combat: a situation similar to self-defense scenarios. Second, its slightly smaller case allows more rounds per magazine, and you can never have too much ammo! Lastly, it performs well in short-barreled rifles (SBR) and while shooting suppressed.

The 300 Blackout wins this section because it was created for close-quarters combat.

Cost & Availability

Owning the latest and greatest cartridges is cool, but most of us must stick to a budget if we enjoy living indoors and feeding our family. That’s why cost and availability should be considered.

Even though it’s the newer cartridge, the 300 Blackout has been more widely adopted than the 6.5 Grendel. That means 300 BLK ammo is a little more abundant and slightly less expensive. You also have a more comprehensive selection of bullet weights and designs from factory loads when you go with 300 BLK.

With that said, the 6.5 Grendel is a reasonably priced and widely available rifle cartridge. It’s popular enough that many of the major ammunition manufacturers produce 6.5 Grendel ammo at a competitive price, with varying bullet styles and weights.

The 300 Blackout wins this section with more availability and lower overall cost.

6.5 Grendel vs 300 Blackout Ballistics Charts

This is the moment all the number crunchers have been waiting for: the ballistics tables!

Read the full breakdown ➜ https://ammo.com/comparison/6.5-grendel-vs-300-blackout

Source: https://freedombunker.com/2025/12/18/6-5-grendel-vs-300-blackout/