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 | 300 Blackout | |
|---|---|---|
| Parent Case | 220 Russian | 221 Fireball/ |
| 223 Remington | ||
| Bullet Diameter | 0.264" | 0.309" |
| Neck Diameter | 0.293" | 0.332" |
| Base Diameter | 0.439" | 0.3759" |
| Case Length | 1.520" | 1.368" |
| Overall Length | 2.260" | 2.260" |
| Case Capacity | 35.0 grains H2O | 25.1 grains H2O |
| Max Pressure (SAAMI) | 52,000 psi | 55,000 psi |
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).
Continue reading 6.5 Grendel vs. 300 Blackout: Which One Is Better? on Ammo.com