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300 Blackout vs 556: More than a Matter of Distance

The origin story of 300 Blackout involves a quest for a better-performing round, infused with the nuances of evolving military operations, and expanding market for suppressors and shorter firearms. While some of the performance requirements focused on creating a round ballistically superior to 9mm when subsonic, and 7.62×39 when supersonic, it had to be fired out of an AR-15 or M4, with minimal replacement of parts. The necessary rivalry ensues to this day: in a battle of 300 Blackout vs 556, which is the superior round?

Considering that the 300 Blackout cartridge was designed with a specific application in mind: engagements within 300 yards, most likely at night, and using a suppressed firearm, we'd expect it to outperform 5.56. Coming to a conclusion over 300 Blackout vs 556 requires parsing both situations and factors. In this article, we will cover both, and include some tertiary information involving 9mm as well.

300 Blackout vs 556 Factors

Cost Per Round / Ammunition Availability:

Instead of wrapping up this article with the logistical question, we begin in the spirit of the phrase “Amateurs talk about strategy and tactics. Professionals talk about logistics and sustainability in warfare,” by General Robert Barrow of the U.S Marine Corps. This will have different implications for military and police units fielding 300 Blackout than it will for those without access to government funding.

The older 5.56 round has enjoyed decades of service, and with it, market support across disciplines. As a result, more established research regarding the impact of barrel length, twist, and the particulars of the gas system, as well as bullet grain weight and construction translate to more available types of ammunition for 5.56. Competitions shooters have developed competition loads, as well as hunters, and the adoption of 5.56 NATO by multiple militaries simply means there's more of it to go around, more spare parts for your firearms in circulation, and more available at a lower price when buying off the shelf.

When considering 300 Blackout vs 556, the rule is simple: for most, achieving a reliable and affordable supply of 5.56 will be more attainable.

Foot-Pounds at Point of Impact:

What gets measured, gets managed. By comparing the ft-lbs pressure at the point of impact, controlling for barrel length and distance, we see the merits of both rounds.

The kinetic energy of a projectile is typically measured in ft-lbs of force, using the equation as follows:

Bullet Mass x Bullet Velocity 2 / ( 2 x dimensional constant x 7000 )

Traditionally the equation uses 32.163 as the numerical coefficient for the dimensional constant.

At the time of writing, most 300 Blackout vs 556 comparisons use rounds fired from 16-inch barrels, which communicates some of the differences but is an odd choice considering the origins of 300 Blackout. We are mostly interested in ft-lbs of force delivered at distances under 300 yards from a 10.3-inch barreled AR-based firearm.

300 blackout vs 556 ft-lbs chart
The above graph does not depict bullet drop at distances, only foot-pounds of delivered force.

The 62-grain M855 round adopted by the military performs best out of barrels no shorter than 10.3 inches. Out of a MK18, “Green Tip” M855 leaves the barrel at roughly 2,600 feet per second, with 930 ft-lbs of force. By 100 yards, the velocity has dropped to 2,309 fps, with 733 ft-lbs of force. At 200 yards: 2,037 fps and 572 ft-lbs. At 300 yards: 1,785 fps, with 438 ft-lbs of pressure.

At the muzzle, the ft-lbs delivered by a 150-grain 300 Blackout round will reside around 1020, at a supersonic velocity of 1750 fps: nearly a 10% improvement, not to mention the physically larger projectile. At 200 yards, the same projectile carries 830 ft-lbs, compared to 572, and 745 ft-lbs at 300 yards: a 70% increase.

Bullet Drop

However, it comes down to more than mere force, for at 200 yards, the 150-grain 300 Blackout round requires 15 inches of compensation due to the heavier, compared to the 2.4-inch demands of a 5.56 “Green Tip” round fired out of the same barrel length.

300 blackout ammunition boxes

Subsonic, starting at a considerably lower velocity, maintains its force but drops nearly 2 feet by 150 yards.

Combining these two factors, we see that in comparing 300 Blackout vs 556, the prior delivers greater force, but requires more compensation for bullet drop, which ultimately limits its effective range to about 300 yards depending on the load and optic. With the right hardware, load, and skill, it delivers a more effective round, re-challenging the concept of an intermediary cartridge.

300 Blackout vs 556 Scenarios to Consider

Personal/Home Defense

The single most important factor dictating the advantage that either round might provide regarding 300 Blackout vs 556 will always be training and practice. For some, becoming proficient with 300 Blackout in the year 2021 is cost-prohibitive considering the availability of ammunition. At the time of writing, the cost per round of 300 Blackout easily exceeds $1, depending on the load. Even though we have not achieved pre-pandemic prices, training ammo for 5.56 is starting to dip below $.45 per round.

As a result, some have the opportunity to train with and utilize 300 Blackout's specific advantages. However, it is not a game of classism as much as skill level and time behind the firearm. The 300 Blackout round is designed for a shorter barrel, a commonly listed factor when choosing a home defense firearm and setup, it presents itself as an ideal option for the urban confines of home defense. At the same time, 5.56 NATO

Hunting

Terrain and Game dictate what the hunter considers a long shot. In much of the Midwestern United States, many hunters average a 100-yard shot on a Whitetail, while in some places, tagging an Elk closer than 400 yards away sounds like a fantasy. Some areas prohibit the use of 5.56 for hunting certain game, which coincidentally reside in areas ideal for the advantages of 300 Blackout.

Bolt-Action firearms chambered in 300 Blackout played a part in the success of the caliber, and continue to appear. Earlier this year, B&T announced the SPR300 Pro: an integrally suppressed rifle that could fulfill the needs of both a hunter and law enforcement.

B&T SPR300 Pro cover
B&T SPR300 Pro

Both/And Considerations

The similarities between both 5.56 NATO and 300 AAC Blackout come with some cautionary warnings. While in the grand scheme of calibers, they perform relatively similar in regards to felt recoil and self-defense range trajectory, one. of the single greatest hazards is mixing ammunition. A 5.56 Nato round will likely not detonate in a 300 Blackout chamber, but the inverse can be deadly. Since it is possible for a 300 Blackout round to seat in a 5.56 chamber, if ignited, all the force of the internal combustion may tear apart the receiver close to the shooter's body.

In regards to the trajectory, cross-training requires an intimate knowledge of both calibers, and the mental awareness to know which you are holding: a feat in the throes of a life-or-death situation. This is only further exacerbated by the drastic difference between subsonic and supersonic 300 Blackout ammunition.

Loose Rounds

The nuanced advantages of 300 Blackout over 5.56 NATO paint each round as still having a place in the market. Even though 300 BLK doesn't outperform 5.56 in every category: be they the socio-economic gap of cost-per-round, or the increasingly less esoteric world of reduced-signature nighttime shooting, it continues to gain momentum in multiple fields of interest.


More on 300 Blackout

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