Fenix Ammunition: A Ballistic Comparison of 5.56x45mm vs. .300 AAC Blackout

This article comes from Fenix Ammunition and is reprinted with permission gained via Twitter DM on 2/17/21. Fenix Ammunition has recently made the news because it forces anyone wishing to do business with them to check a box certifying that they did NOT vote for Joe Biden. It is largely symbolic but I also think it does make the person who did vote for them think harder about their choice. They have a great Twitter and they are outspoken Patriots. Check out their products here and, if you order anything, let them know we sent you!

Picture courtesy of The Truth About Guns.


The .300 AAC Blackout (aka .300 BLK, 300 Blackout, and 7.62 x 35mm) cartridge was developed by Advanced Armament Corporation and submitted for standardization to the Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI) and approved in 2011. The .300 BLK was developed in response to requests from the military for a standardized cartridge with more energy on target and “punching” power than the standard 5.56x45mm NATO cartridge at close and medium ranges, while maintaining the standard 30 round magazine of the government issued M4/AR-15 rifles.
Advanced Armament was able to achieve this by shortening a .223 Remington/5.56mm brass case and then “necking” up the brass case to utilize a larger, heavier .308”/7.62mm diameter projectile. Since the .300 Blackout shares the same case head dimensions as the .223 Remington / 5.56mm NATO cartridge, it allows use of the same bolt carrier group and magazines as a standard M4/AR-15, making conversion as simple as swapping the barrel and muzzle device. This has made the round extremely popular with the civilian AR-15 market for target shooting, hunting, and defensive use.
Despite reams of data, there is much debate regarding the ballistic advantages and disadvantages of 5.56x45mm as compared to .300 AAC Blackout.  In this article, we will discuss several distinct advantages to .300 Blackout primarily in Close Quarters Combat (CQB) and defensive situations.
Projectile Frontal Area
A major advantage of .300 Blackout is the increased “Frontal Area” provided by the larger diameter .308” caliber projectile.  Frontal Area is the total area of the circumference of the cylinder represented by the projectile facing the target.
Projectile-Frontal-Area-Comparison-224-versus-308
All things being equal (velocity, projectile expansion upon impact, etc.), projectiles with a larger frontal area crush/tear more tissue than those with a smaller frontal area, thereby increasing the capacity for wounding.  To provide some comparison, the difference in frontal area between a .308” projectile and a .224” projectile is much larger than the difference between .45 ACP and 9mm.

  • For example, going from 9mm (0.354″) up to .45 ACP is a 27.2% gain in frontal area
  • Going from .224” to .308” is an 89% gain in frontal area

MAXIMUM EFFECTIVE RANGE
The US Military rates the Max Effective Range of the M4 as 500 meters for a point target.  Using 500 meters as a benchmark, a NATO standard 5.56x45mm M855 projectile fired at 2,900 FPS will have 100 inches of drop, 41 inches of drift, and 291 ft.-lbs. of energy at that distance.
In contrast, a .300 Blackout 125 grain projectile at 2,220 FPS has:

  • 100 inches drop at 440 meters
  • 41 inches drift at 484 meters
  • 291 ft-lbs of energy at 700 meters.

What does this illustrate?  By the math, .300 Blackout will experience greater drop due to being fired at a slower velocity, thereby increasing the amount of holdover required to hit a target at the same distance.  However, due to the increased weight of the projectile, it will provide more kinetic energy on target at 500 meters and will provide the same kinetic energy as the 5.56 M855 cartridge out to 700 meters.
While the 300 AAC Blackout has far more energy, the military’s primary statistical benchmark is a calculation known as “Hit Probability”. Hit Probability removes kinetic energy from the equation and focuses solely on the likelihood of connecting with a target at a known distance.  The primary factors affecting hit probability include the impact of wind and barometric pressure on the projectile in flight, and the loss of velocity in flight resulting in the projectile drifting from the point of aim.
If we consider that the drift and drop range is correlated with hit probability, the US Military has calculated that a .300 Blackout 125gr cartridge fired at 2,200 FPS has an equal probability of hitting the target at 462 meters compared to the 5.56 NATO M855 projectile at 500 meters, a loss of only 38 meters.
While this APPEARS to be an advantage in favor of 5.56x45mm, the US Military has also shown through extensive data analysis that the average engagement for infantry units is LESS than 300 meters.  Therefore, maximizing ballistic energy and hit probability INSIDE 300 meters should be considered the primary factor for choosing a caliber for the vast majority of military operations.

Using 300 meters as the benchmark, we can compare the energy of the two cartridges assuming identical atmospheric conditions:

5.56x45mm NATO 55gr M193 (9″ barrel) .300 AAC Blackout 110gr V-Max (9″ barrel)
Range (Yards) Velocity (FPS) Energy (ft.-lbs.)   Range (Yards) Velocity (FPS) Energy (ft.-lbs.)
0 2591 820 0 2,116 1,094
50 2418 714 50 1,985 962
100 2252 619 100 1858 843
150 2092 534 150 1738 738
200 1938 459 200 1624 644
250 1793 392 250 1515 561
300 1656 335 300 1415 489
350 1527 285 350 1324 428
400 1408 242 400 1242 377
450 1303 207 450 1171 335
500 1210 179 500 1111 302

 
At 300 yards, the .300 Blackout projectile retains 154 ft.-lbs. GREATER kinetic energy than the 5.56 NATO projectile, equal to a 45.97% increase.  At 50 yards, the difference is 248 lb.-ft. or a 34.73% advantage.  99.9% of civilian defensive firearm encounters happen within 15-25 feet, making close-range ballistic energy even more important.
IMPACT OF BARREL LENGTH ON CARTRIDGE PERFORMANCE
One of the problems facing the development of the 5.56x45mm NATO cartridge was the initial use of 20” and 24” barrels for the M16A1 platform.  As time has progressed, the military has moved increasingly toward shorter barrels due to the tight spaces soldiers face in urban warfare settings.  Additionally, concerns about hearing loss and Traumatic Brain Injury (TBI) from repetitive automatic fire has led to an increased use of sound suppressors on the M4 rifle.  In order to prevent soldiers from having to wield awkwardly long weapons, it has become necessary to shorten barrel lengths to provide a compact weapon system suitable for CQB environments.
Unfortunately, there is no free lunch.  Shortening barrel length reduces the muzzle velocity of the 5.56 NATO cartridge significantly, reducing its maximum effective range and INCREASING the amount of bullet drop / wind drift experienced at longer engagement ranges.  The table below illustrates a comparison of the two cartridges fired out of various barrel lengths:

This demonstrates a distinct advantage in favor of .300 Blackout ballistics when fired from two of the most common barrel lengths for the modern M4 carbine – 14.5” and 9”.  Due to greater kinetic energy stored in the heavier .308” caliber projectile, the reduction in velocity does not affect hit probability to the degree it affects the 5.56x45mm cartridge.
Referring to our earlier data, using M4 military standards, the max effective range of .300 Blackout from a 16-inch barrel was determined to be 460 meters.
HOWEVER, when fired from a 9-inch barrel at 2,050 FPS, we can calculate the following:

  • 100 inches drop at 410 meters
  • 41 inches drift at 470 meters
  • 291 ft-lbs of energy at 625 meters

This equates to a 440-meter max effective range when fired from a 9-inch barrel, a reduction of only 20 meters.  This will not meaningfully impact the usefulness of the round because our average engagement is well within 440 meters.
BARRIER BLIND POTENTIAL
An important factor for military engagement and law enforcement is the potential for a projectile to be ‘barrier blind’.  Barrier blind refers to the tendency of a projectile to deviate from its path when encountering an obstacle.  For example, a frangible projectile fired at a sheet of AR500 steel would be considered 0% barrier blind, while a modern armor piercing projectile fired at a piece of notebook paper would be considered 100% barrier blind.
Obviously, the construction of the projectile plays a role in barrier blindness but all things being equal, a projectile with greater kinetic energy will deviate from its path LESS against identical barriers than a projectile with a smaller amount of kinetic energy.  Refer to the illustration below:
Due to the greater kinetic energy of the heavier projectile, .300 Blackout enjoys a greater degree of barrier blindness against common barriers – windshield glass, plywood sheeting, heavy clothing, and sheet metal commonly used for vehicle panels – than the 55, 62, and 68 grain projectiles used in the most common 5.56 NATO ammunition cartridges. 300 AAC blackout barrier blind performance
Barrier blindness is a ‘tradeoff’ that must be considered for private citizens when choosing a home defense caliber.  Despite increased hit probability at shorter range, it is inevitable that one must consider what happens to a projectile that misses its intended target – barrier blindness means a greater potential for striking innocent civilians in the proximity of engagement.  However, this can be greatly mitigated through proper projectile selection.  A home defense projectile for civilian use should expand and/or fragment upon impact to prevent overpenetration of barriers such as common interior partition walls, kitchen cabinets, and the like.
Luckily for private citizens, the .308” caliber projectile is one of the most common in the world and has only improved after the development of .300 Blackout.  While the military is preventing from using hollow point and fragmenting projectiles by our adherence to the Hague Convention of 1899, private citizens have access to a much larger range of projectiles, each with different purposes.  Hornady, Barnes, Speer, Swift, and many other manufacturers produce .308” caliber projectiles designed to expand and fragment in soft tissue, maximizing damage to the intended target and minimizing the risk of overpenetration causing damage to unintended targets.
FINAL CONCLUSIONS
Looking at the raw data, the choice seems clear: .300 Blackout is the superior caliber choice for short range engagement, especially when using carbines equipped with shorter barrels.  While the cartridge has not and will likely never completely replace the 5.56x45mm NATO cartridge, there are numerous special forces units, private security contractors, and even law enforcement units who have made the switch.
For a private citizen looking to field a carbine for home defense, the same methodology can be applied.  Greater hit probability,  greater kinetic energy, no loss of magazine capacity, and a wide selection of ammunition choices add up to a fantastic cartridge specifically designed for this purpose.

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About the Author: Patriotman

Patriotman currently ekes out a survivalist lifestyle in a suburban northeastern state as best as he can. He has varied experience in political science, public policy, biological sciences, and higher education. Proudly Catholic and an Eagle Scout, he has no military experience and thus offers a relatable perspective for the average suburban prepper who is preparing for troubled times on the horizon with less than ideal teams and in less than ideal locations. Brushbeater Store Page: http://bit.ly/BrushbeaterStore

20 Comments

  1. Anonymous February 19, 2021 at 10:13

    4.5

  2. Green Mountain Shooter February 19, 2021 at 10:28

    Very informative article. I’m shooting a 7.62×39 upper (Daytona Tactical) that is actually a .308 bore allowing me to take advantage of all of the 125 Gr bullets on the market. I like to refer to it as the .308 Short. It shoots 1″ groups at 100 yds with my handloads and is my MSR for hunting.

    • James February 20, 2021 at 08:55

      GM,have the same upper,with the right mags(csm I think) feeds all steel case flawlessly!That upper has been unavailable for a bit now,lucky for some guys friend he ordered 2 and after trying said guys friend immediately bought the second upper!
      Was a great choice while the 7.62 lagged behind other price increases in cartridges.
      We are still dialing them in but are for most part very happy.

  3. Johnny Paratrooper February 19, 2021 at 10:43

    This is a work of genius. Also, I love Fenix Ammo’s twitter feed. They sold half a million rounds in 7 minutes once, At current prices.

  4. Mike February 19, 2021 at 11:33

    If only it didn’t cost double what 5.56 does per round. This is why I shoot 7.62×39, aka poor man’s 300blk. It has essentially all the same properties as 300blk except compatibility with AR-15 mags and lowers, but is much cheaper to get in bulk.

    • FlyBy February 20, 2021 at 00:27

      How do the 7.62×39 ballistics compare to the 300BO? Yeah, I know, I can do the work and look it up myself and I will. But I’m hoping someone with experience shooting both rounds could weigh in and provide some examples and opinions.

    • NOG February 20, 2021 at 15:33

      The only problem I have with a 7.62X39 AR is the Russian made ammo. I have shot a lot of it in my WASR. Been a great combo in the AK but it is stinky dirty stuff. A buddy of mine got a early AR 7.62X39. He had constant problems with functioning. The AR direct impingement system made it hard to keep clean. Now a Piston AR in the caliber should do just fine. I suspect shooting quality made US ammo might help that but at much more cost. In the end he just sold it. I prefer a 5.56 AR using quality soft point ammo. Federal Fusion 64gr soft points I think will do just fine. If they need shooting once just shoot them twice!

  5. Matt Bracken February 19, 2021 at 12:07

    And this excellent piece did not even address another utility inherent to .300BO, namely, the availability of subsonic 220 grain loads for truly quiet suppressed applications. I just snagged this off the inteweb, below is an excerpt and the link.
    SUBSONIC 300 BLACKOUT BALLISTICS TEST
    It’s that last type of rounds that we’ll be testing today. Subsonic .300 Blackout rounds are a bit of an outlier in the world of rifle ammunition. As they don’t break the sound barrier when fired, they are quieter to shoot than supersonic ammunition. At around 220 grains, subsonic 300 Blackout ammo weighs about as much as .45 ACP, and travels about as fast as .45 as well. However, they have a shape that is much more aerodynamically efficient than .45 ACP, which allows them to fly more accurately and retain more energy at longer distances than .45 ACP typically does. What’s missing, though, is any indication of what a subsonic .300 Blackout round does when it hits the target, and that will play a big part in our test of .300 Blackout subsonic ballistics.
    https://www.ammoman.com/blog/subsonic-300-blackout-ballistics/

    • Johnny Paratrooper February 19, 2021 at 12:49

      I have about 50 rounds through my friend’s Suppressed .300 Blackout. It’s like a dream gun. Hollywood quiet. And it shoots a 2 inch group @ 100 meters. There are not nearly as many drawbacks to the platform as some of the detractors claim. It is, however, something you need to keep track of with a meticulous attention to detail. You can blow up your 5.56 gun if you accidentally chamber a .300 blackout.
      The general consensus for this video is that someone accidentally loaded a .300 blackout in this 5.56 gun.
      https://www.youtube.com/watch?v=WBUE0S6rMv4

      • Matt Bracken February 20, 2021 at 06:59

        Likewise a .270 into a 30-06 etc. For a squad, platoon and up, mixing 556 and 300BO in mags and rifles of the same appearance would be a risk. This risk is not present with a mix of ARs and AKs, obviously. 300BO is interesting, and may provide advantages, but not enough to overcome the fact that almost everybody I know has settled on 556 ARs or 762×39 AKs, and by far most of them are ARs.

      • James February 20, 2021 at 08:49

        Johnny,you are so right on keeping the two apart!
        Lets just say some guy decided to get a .300 upper for his AR,liked it,decided to just do a complete separate build for said upper.Cool,both have skeleton stocks/nice slings/same length hand guard/mounted optics and BUIS,in fact,how cute,they are twins!Hmmmm…..
        The smart person would mark some mags with indelible white marker .300 and perhaps mark dust door .300(on the .300!).
        Smart person might even spring for some mags that are stamped very clearly .300.
        Finally,smart person would only break out one or the other when practicing,tis a good way to ensure one does not end up in the news or on video having a major “oooooppppppsssssss”moment.
        That said,the .300 a legal hunting round in most states while 5.56 not considered one,another bonus to .300.

    • TINVOWOOT February 19, 2021 at 21:32

      The Hornady Sub-x 190gr bullet is built to expand at subsonic speeds. The bullets are available occassionally as reloading components and it’s not hard to replicate the Hornady factory .300BO load.

    • Michael February 20, 2021 at 01:27

      Hello Matt. I prefer the noise because a 147gr 300BO travel at 2300fps from a 8-1/2″ barrel. I was hearing a report about the 2100-2300fps velocity, regardless of caliber, having a special effect on the central nervous system that ends it… I like that so long as you’re on the move and not waiting around for the hyenas to get there. Patrols are better defense of the home than defending your home from inside of it. Patrol strategy and tactics need to be understood and practiced by neighborhood watch operators in advance of engagements, rendezvous points and methods of travel to rendezvous points based on threat levels declared over LoRa group channel or radio to all operators 24/7 or kind of a minuteman response to all these stay behind networks.
      If it’s ok I’d like to ask an off topic question because I cannot find it anywhere else – Suidlanders have created a Civil Defence Force / Initiative in South Africa with over 200k paid members using rendezvous echelons further and further away from cities depending on the threat assessment. How do we here of these united States create our very own “non-State” CDF and would that be wise in terms of emergency medical evacuations, my wife is a medical doctor with 6000 former patients in blue cities, de-escalating conflict on approach to covid checkpoints without stopping for the fake test and the beast shots.

    • MTHead February 20, 2021 at 13:10

      At the shop, we found that if the cartridge ogive. Where it reached the .224 diameter was the same OAL on both cartridges then you were in danger of being able to chamber one in the other. Sadly, that same length is where they feed best also. It’s a problem not to be trifled with.

  6. Brad February 19, 2021 at 12:22

    Another advantage. Blackout has less felt recoil than any of the popular Calibers. Bar far my favorite round for an AR.

  7. MTHead February 19, 2021 at 13:31

    A real fun part about 300 blk.. If you hand load is you can shot any 30 cal. bullets you can get your hands on.
    Find an old box of round nose at a garage sale? Fun, cheap practice! If you have a single-shot and a suppressor. You have the ultimate survival rifle.

  8. Brad February 20, 2021 at 00:37

    I hope this is OK. But I want to recognize a great barrel manufacture that we use exclusively on AR 15 platforms. Green Mountain Barrels is a great barrel manufacturer. Super accurate, chrome plated, and great service. If your so inclined to build a Black out or a 7.62 by 39 their quality shows up in accuracy. A great company. They also manufacturer a 223 Wilde 18 inch barrel that is crazy accurate. Check them out. I should mention very reasonably priced.

  9. Cavguy February 20, 2021 at 09:09

    Easy enough to build a Frankenstein gun, 7.62 x 39 on a AR frame. After the gun is done the only other hiccup is the mags are special. After that all the muscle memory is the same. Well cept for the ballistics but thats easy enough to train.
    Cavguy

  10. Anonymous February 20, 2021 at 10:06

    5

  11. hitman February 20, 2021 at 10:22

    Just scored some Hornady .308 125 gr Hollowpoints for a decent price and Hornady 6.5 123 gr BTHPs (for you Grendel Shooters) for an even better price from Wholesale Hunter.

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