300 Blackout vs 458 Socom

Every few years, dozens of calibers come and go, but not usually those from ammo makers tied into military contracts. Today’s article titled the 300 Blackout vs 458 Socom will present a story about cartridges with similar soldierlike backgrounds but somewhat different purposes.

The main difference between 300 Blackout and 458 Socom is caliber size: the 300 Blackout measures .308” (7.8mm), while the 458 measures 0.458” (11.63mm). The .300 BLK can shoot lighter bullets at higher velocities, while the .458 SOCOM fires wider and heavier bullets than the .300 BLK, offering more massive knockdown power due to the larger caliber.

The .300 Blackout and .458 Socom are remarkable rounds that made a real breakthrough in fixing the issues with their famous predecessor. For our less well-informed readers, the mentioned ancestor is actually the quintessential .223 Remington/5.56×45 NATO cartridge.

In the table below, we will compare the 300 Blackout and 458 Socom dimensions, muzzle velocity, kinetic energy, bullet drop, and free recoil energy for both cartridges:

	.300 Blackout	.458 Socom
Bullet	110 to 265 gr (7.1 to 17.2 g)	200 to 600 gr (12.9 to 39.0 g)
Bullet diameter	.308” (7.8mm)	0.458” (11.63mm)
Case length	1.368” (34.7mm)	1.575” (40mm)
Maximum overall length	2.26” (57.4m)	2.26” (57.4mm)
Rim diameter	.378” (9.6mm)	.473” (12.01mm)
Muzzle Velocity (1)	110 gr/ 2,350 fps	300 gr/ 1,845 fps
Muzzle Velocity (2)	208 gr/ 1,020 fps	500 gr/ 1,075 fps
Muzzle Energy (1)	110 gr/ 1,349 ft-lbs.	300 gr/ 2,267 ft-lbs.
Muzzle Energy (2)	208 gr/ 480 ft-lbs.	500 gr/ 1,283 ft-lbs.
200yds Bullet Drop & Energy (1)	110 gr/ -6.6 inches 824 ft-lbs.	300 gr/ -12.1 inches 1,274 ft-lbs.
200yds Bullet Drop & Energy (2)	208 gr/ -34,1 inch 425 ft-lbs.	500 gr/ -34,6 inches 925 ft-lbs.
Powder load	19.2gr	35.0 gr
Max Pressure (SAAMI)	55,000 psi	35,000 psi
Rifle Weight	7.5 lbs.	7.5 lbs.
Free recoil energy	5.36 ft-lbs.	24.14 ft-lbs.
Case capacity	68.0 gr H2O	59.5 gr H2O

300 Blackout vs 458 Socom: History & How It All Started

In the first post-war years, the U.S. Army correctly anticipated that the infantry would fight new battles at significantly shorter distances than in the previous war conflicts. So, they searched for an intermediate cartridge that would also require a lighter rifle of smaller dimensions.

During the early fifties, the .308 Winchester/7.62x51mm and M14 battle rifles were successful replacements for classic full-size battle rifle cartridges. However, this short-termed solution was soon inherited with the new cartridge–rifle combo known as the 5.56mm – M-16 assault rifle.

The new weaponry was deeply appreciated in the jungles of Indochina, but on the Middle East and Africa battlefields, the standard 5.56 ammunition was somewhat anemic.

In particular, during the battle of Mogadishu in 1993, the U.S. military concluded that the 5.56 in the M4 carbine wasn’t up to the task against their Somali opponents, usually high on drugs.

From that unpleasant experience, the Army started looking for more powerful cartridges for the AR-15.

Interestingly, a hundred years ago, the lack of stopping power against natives was the same reason for introducing the bigger, more effective cartridge. In that case, the U.S. military only adopted a .45 ACP caliber pistol round capable of defeating the drugged-up Muslim Moro ‘Juramentado’ warriors in the Philippines.

The AR-15-style rifles are among the most popular shoulder-fired weapons today and are definitely part of American culture.

Designed in the mid-1950s and initially chambered in the 5.56/.223 Remington, the AR-15, with the arrival of the new millennium, become known as the modern sporting rifle (MSR).

The new cartridges compatible with the A.R. platform started popping up, resulting in more than 50 alternate AR-15 ammo rounds, including wildcat cartridges.

Generally, we can classify them by size:

• Subcaliber (.22 caliber)
• Mid-size (6.5mm and .30 caliber)
• Big bore rounds (.45 caliber and larger)

.300 Blackout (BLK)

The .300 BLK (Blackout) is an intermediate-class rifle cartridge built to overcome the poor stopping power of the 5.56 NATO ball round.

With its primary role to be fired from the short barrels and shot suppressed, the .300 Blackout SBR (Short, Barreled Rifle) was purpose-built to replace the MP5SD, a 9mm sub-machine gun, a primary weapon for close-quarters combat.

In 2010, Robert Silvers, a director of Advanced Armament Corporation (AAC), engineered and released the bottlenecked .300 AAC Blackout at the request of the U.S. government. It was designed by further improvements on a wildcat cartridge known as the .300 Whisper.

Unlike most conventional rifle cartridges, the .300 AAC Blackout can be loaded with relatively lightweight or very heavy for caliber bullets providing two distinct levels of performance.

Since these massive projectiles run at speeds slower than 1,126 fps (speed of sound), the .300 BLK can be easily and effectively suppressed.

This multi-purpose cartridge achieves supersonic velocities using lighter bullets of 110, 125, and 147 grains. Otherwise, it stays subsonic when firing heavier bullets in the range of 200–250 grains.

As for the terminal ballistics, the .300 Blackout delivers similar ballistics to the 7.62×39. However, with more oomph, it beats the 5.56 NATO in energy transfer, offering better energy retention and penetrative abilities.

Though designed as a specialty round for military and home defense applications, the .300 Blackout is also offered in many commercial loads. These loads have performance better suited for hunting medium to large game such as hogs and deer.

Without question, the .300 Blackout is an outstanding all-around caliber suitable for many applications, from home defense, hunting and target shooting.

Speaking of .300 BLK as a hunting round, the general consensus is to use lighter supersonic ammunition to get its full ballistic potential.

The .300 Blackout has a practical range of about 300 yards loaded with a supersonic round, whereas hunting with subsonic rounds is recommended only if the animal is within 100 yards. In fact, when comparing the .300 Blackout vs 458 SOCOM, the .300 BLKs’ higher velocity is the primary advantage over the .458 SOCOM.

Another most apparent difference between the .300 BLK vs. .458 SOCOM is the bullet diameter. The .300 AAC Blackout has loaded with projectiles diameter of 0.308 inches, and the .458 SOCOM uses bullets with a diameter of 0.458 inches.

Although having different calibers, case lengths, and rim diameters, these two centerfire cartridges have the same overall length to fit into the AR-15 rifle action and STANAG 5.56 magazine.

Since the .300 Blackout cartridge was initially designed around the idea of being suppressed, most suppressors would work exceptionally well mounted on a .300 Blackout firearm.

As a dual-role cartridge, the .300 BLK is beneficial when loaded with subsonic ammo and a mounted suppressor. When shooting subsonic rounds, you can expect it to be as loud as a suppressed .22 L.R. rifle.

Besides, the suppressors can be fast attached using a standard 5/8×24 direct thread mount.

Finally, the .30-caliber suppressors are more common, so you can more easily find them on the market than specifically made suppressors for the .45-caliber.

While these cartridges can function in an A.R. pattern rifle, another common feature is an easy conversion. Usually, you can keep your current A.R. lower and magazine and replace only the barrel or upper receiver.

.458 SOCOM

For the powerhouse fans, the .300 Blackout is the first step into large-caliber AR-15s since the civilian interest in the AR-15 and big bore A.R. cartridges grew over the years, particularly for deer, bear, and hog hunting.

But when it comes to heavy-hitting big-bore cartridges designed for use in the A.R. platform firearms, you have a few real choices known as Thumper rounds. Typical cartridges of this concept created by shooting legend Lt. Col. Jeff Cooper are the .450 Bushmaster, .458 SOCOM, and the .50 Beowulf.

The .458 SOCOM was designed by Marty Ter Weeme of Teppo Jutsu LLC in 2000 to offer a higher energy class, fully compatible cartridge with the AR-15/M4 system.

Designed for shots within 250 yards, .458 SOCOM delivers crippling kinetic energy (1,035 ft-lbs) that add massive stopping power to the AR-15 rifle with a simple upper receiver swap.

Similar to other big bore cartridges, the .458 SOCOM was explicitly developed to add punch to the A.R. As a typical sample of the Thumper concept, the .45-caliber SOCOM round does not only hit hard on a big game. Still, it gives a heavy kick in the opposite direction, back to the shooter’s shoulder as well.

When we compare the free recoil of the .300 BLK vs. the .458 SOCOM (5.3 ft-lbs. vs. 25.4 ft-lbs. of recoil), we will find that the .458 SOCOM has roughly five times the recoil of a .300 Blackout round.

Both cartridges have the same overall length, but the .458 has a longer case, 1.575″ vs. 1.368″.

Unlike the typical bottlenecked case of the .300 AAC Blackout, the .458 SOCOM has an exceedingly small shoulder.

Considering the muzzle velocities, the .300 BLK can shoot lighter bullets at higher velocities, producing greater energy than these two calibers. However, the .458 SOCOM fires wider and heavier bullets than the .300 BLK, offering more massive knockdown power due to the larger caliber.

Most .458 SOCOM ammo typically has bullet weights in the 200gr to 600 gr range, with 250gr, 300, and 350 gr bullets being the most popular.

Like the .300 AAC Blackout, the .458 SOCOM can shoot supersonic and subsonic bullets with authority. It is a popular choice for taking down large game animals requiring better penetration to ensure an ethical kill.

As for the magazine capacity, the .300 Blackout vs. the .458 SOCOM, the Blackout can use unmodified 30rnd .223/5.56 magazines with full capacity. The .458 SOCOM can also use standard AR-15 magazines, but they can hold just 10 cartridges of this big-bore caliber.

Furthermore, while the .300 AAC Blackout and the .458 SOCOM are loaded to different pressure levels, both have very similar ballistics.

As for the bullet’s availability, the .458 SOCOM uses the same diameter of projectiles as the famous .45-70. It means the SOCOM has huge pallets of both subsonic and supersonic loads at its disposal.

The .458 SOCOM has a .473″ rim diameter, which can be found on other common cartridges like the .308, .30-06, and .270 Winchester. On the other hand, the .300 BLK has a .378″ rim diameter, which is the same as the 5.56 NATO.

The .458 Socom is often compared to the .50 Beowulf since both rounds are designed for close-quarters combat and maximum stopping power. However, the .50 Beowulf has slightly more energy than the .458 SOCOM as it handles 350 gr through 450-grain slugs of .500 inches.

Some ask if a .458 SOCOM is the same as a .458 Win Mag. Though both rounds use the same 0.458 bullets, they are very different ballistically. The .458 Win Mag cartridge is almost an inch longer than the SOCOM, which results in a higher muzzle velocity of 2,600fps vs. 1,900fps.

Recap: 458 Socom vs 300 Blackout

Obviously, the .458 SOCOM is a harder-hitting round with all these enclosed facts, but it does not make it the perfect “do-it-all” caliber.

The .300 Blackout is the most versatile A.R. cartridge in bullet weights, whereas the .458 SOCOM caters to a narrow audience.

However, both rounds can transform any AR-15 into a capable deer and hog hunting rifle.

Rifles chambered in these cartridges shoot subsonic bullets quickly, but you must admit that the .458 SOCOM is an absolute powerhouse with 200gr to 600gr bullets.