300 BLK Vs. 6.5 Grendel

The 300 Blackout and 6.5 Grendel are great cartridges used in AR-15-type rifles. In the USA, the calibers have made their mark for hunting applications, and it’s not uncommon for an AR rifle hunter to have rifles in each caliber, given each caliber’s unique characteristics.

The .300 Blackout and the 6.5 Grendel are fantastic cartridges for AR-15-type rifles. The subsonic .300 is a perfect close-range cartridge. The .300 BLK is excellent for hunting in more densely wooded terrain where shots are closer, while the 6.5 Grendel is well suited for longer shots.

If you’re considering adding either the 300 BLK or the 6.5 Grendel in an AR-type rifle for hunting, the choice can be pretty confusing. Your desired application for the caliber will play a significant part in your choice. We’ve researched and compared both calibers to assist you in making the right choice.

300 Blackout Vs. 6.5mm Grendel

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The .300 AAC Blackout is the cartridge’s official name but has been designated as the 300 BLK by SAAMI, and to confuse things a bit more, CIP has called it the 300 AAC Blackout, and some refer to the cartridge as the 7.62 x 35.

The 300 AAC blackout was designed in 2009 by AAC (Advanced Armament Corporation) and Remington Defense on particular order for a military Customer needing a .30 caliber cartridge for AR-Type rifles. The cartridge had to offer supersonic and sub-sonic capability in suppressed rifles.

The effective range of the 300 BLK is 500 yards (460 m) using supersonic ammunition.

AAC and Remington ticked all the boxes, and the rest is history. SAAMI approved the cartridge in 2011, and its popularity has soared for many applications. Including the hunting of deer up to the size of Elk.

The 6.5 Grendel (.264”) was developed as a precision low-recoiling cartridge capable of accuracy out to 800 yards (731 m) when fired from an AR-15 type rifle. The cartridge was designed specifically for use in an AR-15 type rifle by Bill Alexander, Arne Brennan, and Janne Pohjoicepaa in 2003 using the .220 Russian parent case.

An excellent feature of both cartridges is that they work superbly in AR-15-style rifles. The only change having to be made to an existing .223 Rem / 5.56mm rifle to accommodate the Blackout is a barrel of the appropriate caliber. The bolt, bolt face, and magazine remain as is.

The 6.5mm Grendel cartridge requires a new bolt head due to its slightly larger case diameter and barrel.

6.5 Grendel Vs. .300 Blackout Cartridge Ballistics Comparison

The 6.5mm (.264”) diameter bullet has been around since 1891. The long, slender bullet is well known for excellent penetration on game animals, having exceptional bullet co-efficient and long-range accuracy, even at relatively low velocities by today’s standards.

The .300 Blackout fires a .30” (7.62mm) diameter bullet, the same diameter as bullets used in the .308 Win, .300 Win Mag, 30-06, and others. It’s thus no surprise that the .300 Blackout has been a hit with AR-15-type rifle fans, many of which most likely own bolt action rifles in .30 caliber.

The below table shows the ballistic differences between the .300 Blackout and 6.5 Grendel:

CaliberBullet Mass (Grain / Gram)Velocity (ft/s & m/s)Energy (ft-lbs & Joules)
.300 Blackout90 gr / 6 g2550 / 7801300 / 1800
6.5 Grendel90 gr / 6 g2880 / 8801658 / 2248
.300 Blackout110 gr / 7 g2375 / 7241377 / 1867
6.5 Grendel108 gr / 6.9 g2790 / 8501866 / 2530
.300 Blackout125 gr / 8.09 g2215 / 6751360 / 1840
6.5 Grendel123 gr / 8 g2650 / 8101917 / 2599
.300 Blackout125 gr / 8.09 g2215 / 6751360 / 1840
6.5 Grendel130 gr / 8.4 g2510 / 7701818 / 2465

As seen from the above comparisons, the 6.5 Grendel is roughly 250 to 300 feet per second faster in terms of velocity with similar bullet weights. Muzzle energy is also in favor of the 6.5 Grendel, with its excellent bullet coefficient due to the long weight and slender bullets, delivering superior long-range terminal ballistics.

The above tables draw a picture from the perspective of .300 Blackout and 6.5 Grendel buyers. Our choice for hunting in more open terrain will be the 6.5 Grendel. When hunting in brush or heavily wooded areas where a good blood trail is required to find the animal after the shot, the .300 Blackout is the one for you.

Both calibers are well suited for hunting deer up to the size of Elk, using bullets between 140 to 150 grains to ensure maximum penetration from all reasonable angles.

.300 AAC Blackout Subsonic Ammunition.

The below table is aptly headed “Something Special.” The drawcard for many Hunters to the .300 Blackout is that factory sub-sonic ammunition is readily available for the caliber and that when used with a decent suppressor, you have a very effective subsonic AR.

Something Special: The above table summarizes the sub-sonic bullet velocity and energy statistics.

CaliberBullet Mass (Grain / Gram)Velocity (ft/s & m/s)Energy (ft-lbs & Joules)
.300 Blackout220 gr / 14 g1010 / 310498 / 675

The 220-grain (14 g) bullet is a fantastic bullet choice. The subsonic velocity will limit shots on game animals to 100 yards to be on the safe side, as bullet drop is a significant consideration at 1010 ft/s.

The subsonic round is an excellent choice for Hog culling or hunting deer at close ranges in more built-up areas where it’s legal.

The high bullet weight ensures significant penetration despite the bullet’s low velocity. Remember the old Martini Hendry rifles 450-grain lead bullet travels at a very similar velocity and is used for hunting many Buffalo and Bison in the past.

We’re not promoting the use of the .300 Blackout on dangerous game, but at close range, the .300 Blackout is deadly on deer. The subsonic bullet velocity causes minimal meat bruising as the hydrostatic shock and the resulting temporary wound channel is significantly less than with high-velocity cartridges.


These two cartridges are fantastic for AR-15-style rifle owners. The.300 Subsonic is a perfect close-range cartridge. The 300 Blackout is an excellent choice for shooting close-up in dense woods, while the 6.8 Grendel is well-suited for long-range shooting. 

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