If you want to increase the stopping power of your standard AR-15 chambered in 5.56 NATO, then converting it to fire 300 Blackout or 6.8 SPC are both excellent options. Both rifle cartridges offer improved terminal ballistics over the 5.56 and function well for home defense, hunting, and general target shooting.

In this article I will provide you with the facts about these two rifle cartridges, and help you decide which is better for your next AR-15.



What's the Difference Between 6.8 SPC and 300 Blackout?

The most significant difference between the 6.8 SPC and the 300 AAC Blackout is that the 6.8 SPC is designed for longer ranges, while the 300 Blackout is optimized for close-quarters combat. A backcountry hunter should pick the 6.8 SPC for longer distances, and a hunter in thick brush should choose the 300 Blackout for shorter distances.

Cartridge Specs



Which Is Better for Hunting?

Both the 300 Blackout and 6.8 SPC are exceptional hunting rounds, even if they aren't designed for that purpose. However, the 6.8 SPC gives hunters an edge with its longer effective range for medium game such as whitetail deer or feral hogs: 250-300 yards, as opposed to 150 yards for the 300 Blackout.

The 300 Blackout offers shooters a low-recoil option that works well for varmints like groundhogs and coyotes. The 6.8 SPC can also do the same job, but at the cost of higher accompanying recoil.



Which Is Better for Deer Hunting?

Determining which cartridge is better for deer hunting really depends on the area where you hunt and the range at which you expect to shoot a deer. If you hunt in a densely forested area (like I do), then a 300 BLK's 150-yard effective range should prove more than sufficient. However, if you plan on taking longer shots between 150 and 300 yards, then the 6.8 SPC is the better choice.

Home Defense

Shooters often forget how sound bounces off walls, which makes a rifle report sound even louder indoors.

The 300 Blackout plays extremely well with a suppressor and has multiple subsonic ammo options, making it a great choice for home defense.

The lower recoil of the 300 BLK makes it a better choice for close-quarters engagements, as you'll be able to get back on target faster for follow-up shots.

This is not to say that the 6.8 SPC is ineffective at self-defense because it certainly is a potent round.

However, given its substantially higher striking energy, the 6.8 SPC also has a higher likelihood of over-penetration. That increases the risk of a bullet inadvertently striking an innocent bystander.

Combined with a shorter barrel and suppressor, a 300 Blackout AR-15 carbine makes for an extremely lightweight, maneuverable home defense option with plenty of stopping power.

Suppressor Integration

One of 300 BLK's key design features is that it exhibits a complete powder burn in only 9 inches of barrel length. This means it is a perfect candidate for a short-barrel rifle (SBR). Furthermore, 300 Blackout ammo is available in either supersonic or subsonic muzzle velocities, the latter of which is ideal for suppressor use.

Although using a suppressor with 6.8 SPC has minimal downsides, all available ammunition only features supersonic muzzle velocities.

Ballistic Coefficient and Sectional Density



Ballistic coefficient (BC) measures a bullet's aerodynamics and resistance to wind deflection. Sectional density (SD) reflects a bullet's penetration ability based on its diameter and weight.

Typically, longer and heavier bullets have a higher BC as they can resist wind drift more efficiently.

When comparing cartridges loaded with bullets of the same weight, such as the 110 grain V-MAX, the 6.8 SPC has a slight advantage in BC (0.370 vs. 0.290) and SD (0.205 vs. 0.166). That's the advantage it gains by firing longer and more slender bullets than the 300 Blackout.

However, the 300 AAC Blackout is also designed to fire heavier subsonic loads that outstrip the 6.8 SPC in both categories. For example, it is not uncommon for 200+ grain .30 caliber bullets to have a BC over 0.500 and SD over 0.300.

When it comes to BC and SD for the 300 Blackout and 6.8 SPC, whether one truly is "better" than the other heavily depends on which two cartridges are being compared. When their bullets are equal in weight and the same in design, the 6.8 SPC outclasses the 300 BLK; when the 300 BLK is loaded with a substantially heavier bullet, its BC and SD are both superior.

Accuracy



Accuracy is challenging to quantify when comparing two different rifle cartridges, since it is more of a product of the firearm being fired and the skill of the shooter than it is an innate property of the cartridges themselves.

Generally, most shooters prefer a round with lower recoil. It reduces the likelihood of developing a trigger flinch, and also lessens the muzzle rise which throws aim off with each shot. This would suggest that the 300 Blackout makes accurate fire easier. However, the 6.8 SPC has a flatter trajectory, making it the more forgiving cartridge for farther shots.

Although both rounds are incredibly accurate, the 300 BLK makes precision easier during close-quarters battle (CQB), whereas the 6.8 SPC will prove the more accurate option for longer-range (150+ yards) shots.

6.8 SPC vs 300 Blackout Ballistics

6.8 SPC Ballistics

Below you'll find our ballistics tables for multiple factory loads for 300 AAC Blackout and 6.8 Remington SPC. For an in-depth analysis of 6.8 SPC ballistics spanning different bullet weights and manufacturers, visit our comprehensive ballistics resource.

Read the full breakdown ? https://ammo.com/comparison/6.8-spc-vs-300-blackout