458 SOCOM vs 5.56: Big Bore Ballistics in a Standard AR-15

The standard AR-15 chambered in 5.56 NATO is truly America’s rifle and is a symbol of American ingenuity and freedom. Although the 5.56 NATO has proven itself in the jungles of Vietnam and deserts of Iraq, some gun owners wanted something more…

They wanted more stopping power, better terminal ballistics, and a rifle cartridge that could be used for both home defense and big game hunting.

The 458 SOCOM cartridge is the answer that these gun owners were looking for, as its heavier bullets can deliver bone-crushing kinetic energy that can stop feral hogs or whitetail in their tracks.

However, is investing in a big bore 458 SOCOM upper receiver really worth it? Or is it better to stick with the AR-15 platform mainstay, the 5.56 NATO?

In this article we will help you answer these questions and more as we compare the 458 vs 556.

What is the difference between 5.56 and 458 SOCOM?

The primary differences between 458 SOCOM vs 556 is bullet diameter each cartridge fires and the intended engagement ranges. The 458 SOCOM fires a 0.458” diameter bullet that is intended for close-range engagements while the 5.56 fires a 0.224” diameter bullet that excels at long-range shots.

A Note on Nomenclature

Please note that within this article we will refer to the 223 Remington (223 Rem) and the 5.56x45mm NATO round interchangeably. There are differences between the two and you can read about them in this article: .223 vs 5.56

In short, a 223 Rem can safely be fired from a rifle or handgun chambered in 5.56, however the opposite is not true.

Cartridge Specs

When evaluating centerfire rifle cartridges, it’s a good idea to analyze the cartridge specs to gain more knowledge of each.

Perhaps the most striking difference between these two cartridges are the bullets that each fire. The 5.56 fires a 0.224” diameter bullet while the 458 SOCOM fires a massive 0.458” diameter bullet. This directly affects the bullet weight that each cartridge can fire. The 458 SOCOM cartridge typically fires bullets between 250 and 600 grains, with the 300 grain bullet being the most popular. In contrast, the 5.56 fires between 35 and 77 grain bullets with 55 and 62 gr the easiest to find on sporting goods store shelves.

Another striking difference between the two rifle cartridges is their case length and width. The 5.56 round is thinner and longer with a base diameter of 0.377” and case length of 1.76”. The 458 SOCOM is considerably wider than the 5.56 with a 0.541” base diameter but with a shorter cartridge case at 1.575”.

Both the 458 SOCOM and the 5.56 have the same overall length of 2.26” since the 458 SOCOM was designed to fit into a standard AR-15 magazine.

As the 458 SOCOM descended from the might 50 Action Express (fired by the Desert Eagle), it’s not surprising that the cartridge has a distinct case capacity advantage over the 5.56. The 458 SOCOM cartridge has over double the case capacity of the 5.56 at 61.1 gr vs 28.5 gr, respectively. This increased case capacity is needed to propel the incredibly heavy bullets fired by the 458 SOCOM out of the barrel towards its intended target.

The final difference between the two rifle cartridges is their maximum pressure. The 5.56 can handle significantly higher chamber pressures compared to the 458 SOCOM as the 5.56 fires a smaller bullet at higher velocity. The maximum chamber pressure for the 5.56 is established as 55,114 psi compared to 35,000 psi for 458 SOCOM.

Recoil

The 5.56 NATO is well known for being a low-recoil round.

Recoil is an important consideration when purchasing a new rifle as a round with heavy recoil will be more difficult to control and will slow your rate of follow up shots.

Recoil is affected primarily by muzzle velocity (FPS), powder charge, bullet weight, and rifle weight.

The 5.56 averages around 4 ft-lbs of free recoil energy compared to a whopping 23 ft-lbs for the 458. That’s more than a 5x difference in recoil. To put this in perspective, the 458 SOCOM has about 4 ft-lbs less free recoil than a 12 ga shotgun shell.

As the 458 fires projectiles that can be over 5 times heavier (or more!) and double the powder charge, it’s not overly surprising that the 458 SOCOM has considerably more recoil than the 5.56.

Muzzle Velocity and Kinetic Energy

When it comes to muzzle velocity, there are only a handful of rounds that are faster than the 5.56 NATO. However, the 5.56 cannot keep up with the 458 SOCOM in terms of muzzle energy.

For this example, we will compare the Hornady Frontier 55 gr FMJ (M193 clone) for 5.56 and the SBR Ammunition 300 gr Barnes TTSX load for 458 SOCOM.

At the muzzle, the 5.56 round is blazing down range at 3,240 fps compared to 1,835 fps for the 458 bullet. Although this is only one example, essentially every 5.56 factory load will have a higher muzzle velocity than the 458 SOCOM since the 5.56 is firing lighter bullets.

However fast the 5.56 bullet might be, the 458 SOCOM is using a considerably heavier bullet that carries a lot more muzzle energy. At the muzzle, the 458 SOCOM bullet delivers a whopping 2,243 ft-lbs of kinetic energy compared to 1,282 ft-lbs for the 5.56.

Although the 458 SOCOM round has almost double the kinetic energy at the muzzle, the round quickly loses fps and ft-lbs of energy as it travels downrange due to its bullet design. By 300 yards the 300 grain bullet has gone subsonic and by 600 yards it carries around 500 ft-lbs of energy. To put that into perspective, that is still more than a 45 ACP +P round has at the muzzle, but it illustrates the primary difference between 5.56 and 458 SOCOM. In contrast, the 5.56 55 grain bullet goes subsonic around the 700-yard marker.

The 458 SOCOM was clearly designed for close-range shots at self-defense distances where it can use its massive kinetic energy advantage to devastating effect. While the 5.56 had long-range shooting and marksmanship in mind for longer engagement distances.

Trajectory

Trajectory is how we quantify a bullet’s flight path as it travels downrange measured in inches of bullet drop.

Obviously, a flatter shooting cartridge is preferred for long-range shooting, as a shooter will require fewer adjustments to their optics to compensate for bullet drop. Having a flatter trajectory also means that a cartridge will be more forgiving of ranging mistakes.

With its massive advantage in muzzle velocity and bullet design, the 5.56 utterly dominates the 458 SOCOM in terms of trajectory.

Assuming a 100 yard zero, the Hornady M193 clone mentioned in the previous section will experience -11.5” of bullet drop compared to -46.8” for 458 SOCOM. That’s over a 4x difference between the two cartridges.

This difference only increases further downrange as the 458 goes subsonic around 300 yards for most factory loads.

When it comes to trajectory and long range shooting, the 5.56 is clearly the better option.

Ballistic Coefficient

Ballistic coefficient (BC) is a measure of how well a bullet resists wind drift and air resistance. Put another way, it’s a numeric representation of how aerodynamic a bullet is. A high BC is preferred as this means the bullet will buck the wind easier.

Generally, heavy bullets will have a higher BC as it takes more force to disrupt the flight of a heavier bullet than a lighter one. Ballistic coefficient varies from bullet to bullet based on design, weight, and other factors that are beyond the scope of this article.

As the 458 SOCOM fires considerably heavier bullets than the 5.56, it would be easy to assume that the 458 would decimate the 5.56 in terms of BC. However, this is not the case, and the two bullets are similar in terms of their ballistic coefficients.

The major issue with the 458 SOCOM is its bullet design. As it is constricted by the overall length requirement of 2.26” to fit inside a standard AR-15 magazine, 458 bullets must be short and wide to fit in the mag while the 5.56 bullets are slender, streamlined, and aerodynamic.

The 5.56 NATO 55 grain bullet from Hornady will have a BC of 0.243 while the 300 grain TTSX Barnes bullet for 458 has a BC of 0.236. Higher ballistic coefficient values for both rounds can be had by shooting heavier options. For example, a 73 grain Hornady ELD Match for 5.56 has a BC of 0.398 while a Barnes 500 grain TSX for 458 has a BC of 0.412.

Although outliers can be found at extreme variations in bullet weight, generally the 5.56 and 458 SOCOM are about equal in terms of ballistic coefficient.

Sectional Density

Sectional Density (SD) is the measure of how well a bullet penetrates a target. This is extremely important when hunting big and medium sized game, as you need a bullet that can punch through thick hide, bone, and sinew.

Sectional density is calculated by comparing the bullet weight and the bullet diameter. The higher the SD the deeper the bullet will penetrate into the target. This is a simplified view of penetration as there are other factors to consider, such as bullet expansion and high velocity.

The 458 SOCOM excels in terms of penetration due, in part, to its extremely high muzzle energy.

The Barnes 300 grain 458 SOCOM bullet generally has a SD around 0.204 while the 55 grain bullet for the 5.56 has a SD of 0.157.

Sectional density for 5.56 can be increased by using a heavier bullet like a Hornady Critical Defense 73 gr FTX bullet that has a SD of 0.208, but then the heavier 458 SOCOM bullets generally have a SD in excess of 0.3.

In large part owning to its inherent mass and kinetic energy, the 458 SOCOM will generally penetrate deeper into the target than the lighter 5.56 round.

Hunting

In terms of hunting, both rifle cartridges excel in their respective areas of expertise.

The 5.56 NATO/223 Rem is an awesome choice for varmint hunting, where the flatter trajectory makes it a great choice for longer range shots. However, the 5.56 lacks the kinetic energy needed to ethically harvest medium to large sized game like whitetail. Many states and provinces prohibit the use of 0.224” diameter bullets for deer hunting for this reason.

This is where the 458 SOCOM really shines as it has more than enough muzzle energy to easily dispatch a whitetail with relative ease. The 458 is also a favorite of hog hunters who love the semi-auto capability of the AR-15 for its quicker follow up shots when engaging multiple targets.

The 458 SOCOM offers hunters a big bore cartridge that delivers crippling kinetic energy that can take down an elk or even a black bear within 100 yards (1,500 ft-lbs) or a whitetail within 200 yards (1000 ft-lbs). For longer range shots in excess of 200 yards, the 458 will lack the needed kinetic energy to ensure a clean harvest on a game animal. Therefore, for long range shots something like a 308 Winchester or 30-06 Springfield will need to be used instead.

For the varmint hunting enthusiast, the 5.56 NATO is the clear choice. But if you want to hunt anything larger than a coyote, the 458 SOCOM is the better option for big game animals within 200 yards.

SBR and Suppressor Integration

One of the massive benefits of the 458 SOCOM cartridge is its optimization for use in a Short Barreled Rifle (SBR) with or without a suppressor. The 458 was designed to experience a full powder burn in 9.5” of barrel length, meaning that a longer barrel does not increase muzzle velocity. In fact, Marty Ter Weeme, the original developer of the 458 SOCOM cartridge, does not recommend using a barrel any longer than 16” for the round.

The 458 SOCOM was also designed to be used with a suppressor. Heavier loads in excess of 500 grains will naturally be subsonic, making the 458 hearing safe when using a suppressor and subsonic ammo similar to the 300 Blackout. Most 458 barrels use a faster twist rate barrel along the lines of 1:14, but a faster twist rate of 1:10 might be needed to stabilize heavier bullets for barrels less than 10”.

The 5.56 was initially designed with the 20” barrel of the Colt M16 rifle in mind. Although the M4 carbine has been extremely effective in combat, the terminal ballistics of the 5.56 suffer in an SBR.

Furthermore, the direct gas impingement (DGI) system on the AR-15 in conjunction with high pressure 5.56 ammo doesn’t always jibe with using a suppressor. Shooters will often get gas blow back in their face/eyes when using a suppressed 5.56 rifle.

With all this in mind, the 458 SOCOM makes for an extremely potent home defense option as it is ideal for use with a suppressor and SBR. An AR-15 in 458 makes for an incredibly compact, maneuverable, and hard-hitting self-defense package just as it was designed for.

Ammo and Rifle Cost/Availability

The 5.56 NATO cannot be beat in terms of ammo availability and price.

Virtually every ammo manufacturer has multiple factory loads for both 223 Rem and/or 5.56 NATO. As this is the frontline cartridge used by the U.S. military, there are also a plethora of surplus ammo options available on the market.

The popularity of the 5.56 really helps keep prices down and supply up. You can find 223/5.56 ammo virtually anywhere that ammunition is sold.

Sadly, there are not many manufacturers that currently have offerings for 458 SOCOM. Underwood Ammo, SBR Ammunition, and Buffalo Bore are the three major manufacturers who have embraced the 458 SOCOM and have several factory loads to cover most of your shooting needs.

Inexpensive FMJ 5.56 ammo costs around $0.60/round while match-grade ammo usually runs around the tune of $1.50/round and up depending on bullet weight and manufacturer.

As the 458 lacks the widespread popularity of the 5.56, ammo is considerably more expensive for the SOCOM round. The cheapest FMJ 458 ammo starts around $2/round while premium hunting ballistic tip or hollow points start at $3.50/round and go up from there.

For high volume shooting and plinking, the 5.56 is clearly the better option.

Buying in bulk is always smart, make sure to check out our stock of 5.56 bulk ammo.

In terms of rifle availability, the AR-15 platform is the most popular semi-automatic rifle in North America and the most popular chambering is unquestionably 5.56x45mm NATO. However, as the AR-15 can easily be converted to fire 458 SOCOM by changing the barrel and bolt. Standard AR-15 mags can be used for 458 SOCOM without any modification. However, as the 458 is considerably more rotund than the 5.56, you will be limited to a 10-round capacity in standard 30-round AR-15 mags when loading them with 458 SOCOM rounds.

When looking for a bolt-action 5.56 rifle, you’ll quickly discover that most of them are chambered in 223 Rem and not 5.56. It is not safe to fire 5.56 ammo in a 223 rifle as we discuss in this article HERE.

There are, however, several options available for bolt action 5.56 rifles like the Ruger American Ranch, the Ruger GUNSITE Scout, and Mossberg MVP Patrol.

There are currently no bolt-action rifles available in 458 SOCOM from the major rifle manufacturers in North America or Europe. It is possible to have a custom rifle built in 458 SOCOM, but that is an expensive undertaking many shooting enthusiasts don’t have the budget or desire to embark on. This means that if you want to shoot 458 SOCOM, you are limited to the AR-15 platform only.

Reloading

When it comes to 5.56 NATO and 458 SOCOM, reloading is one option that many shooters utilize to reduce their cost per round.

As inexpensive military surplus brass, powder, and bullets are easy to find for 5.56, it is a rifle cartridge that many handloaders enjoy reloading in bulk.

One thing to note is there are not reloading dies specific for 5.56 NATO. As the 223 Remington is dimensionally identical to the 5.56, only 223 Rem dies are available. 

Although the 458 SOCOM is a relatively new cartridge, the major reloading companies like Lee Precision, RCBS, and Redding have dies available in 458 SOCOM. Sourcing brass and bullets is another matter as the 0.458” diameter bullet is not the most common caliber for reloading. Hornady, Barnes, and Sierra have bullet options for 458-caliber. Brass cases for 458 SOCOM are also more expensive are harder to source than 5.56 cases.

Although it is generally more expensive to reload 458 SOCOM than 5.56, the cost savings from handloading your own 458 ammo is a real boon to those who love to plink with their SOCOM rifle.

5.56 NATO Ballistics

Note: This information comes from the manufacturer and is for informational purposes only. The actual ballistics obtained with your firearm can vary considerably from the advertised ballistics. Also, ballistics can vary from lot to lot with the same brand and type load.

A Brief History of 458 SOCOM

In 1993, U.S. Special Operations Forces were dispatched to Mogadishu, Somalia during the Somali Civil War in an effort to capture Mohamed Farrah Aidid. Aidid was wanted in connection to attacks made on UN Peacekeeping forces in 1992.

President Bill Clinton ordered the formation of Task Force Ranger, a combination of Army Rangers and Delta Force operators, after two bombing attacks on U.S. military assets in Somalia. Codenamed Operation: Gothic Serpent, the joint-task force was ordered to hunt down Aidid and his lieutenants and capture them. This culminated in the Battle of Mogadishu and was the basis for the movie, Black Hawk Down.

Task Force Ranger was armed with Colt M16 rifles as well as M4 carbines loaded with 62 grain M855 (SS109) ammo. Many special operations operators reported subpar performance of the round in combat, citing the need for multiple shots to take down an enemy combatant. Somali fighters would often chew on a drug known as Khat, reducing their appetite and increasing their pain tolerance.

The 458 SOCOM was developed in response to a conversation (supposedly at a barbecue) between Marty Ter Weeme of Teppo Jutsu LLC and a member of the Special Operations community who served on Task Force Ranger. The goal was to create a big bore cartridge for the AR-15 that could stop an attacker in a single shot.

The 450 Bushmaster was initially considered for the program; however, the 450 Bushmaster round was quickly eliminated from further consideration as a bottleneck cartridge was needed for improved feeding under combat conditions.

Marty Ter Weeme and Tony Rumore of Tromix finally settled on an elongated 50 Action Express (AE) case necked down to accept a .458-caliber bullet as the final design for the 458 SOCOM. The rim of the 50 AE case was also reduced from 0.514” to 0.473” so it would be compatible with bolt-action rifles. For reference, the 308 Winchester and 30-06 Springfield share the same rim diameter as the 458 SOCOM.

Tromix was contracted to make the first 458 SOCOM rifle in February 2001.

Capable of firing a 300 grain bullet at 1,900 fps with 2,400 ft-lbs of force, the 458 SOCOM offers a massive upgrade in stopping power over standard 5.56 ammo.

The 458 SOCOM is 100% compatible with the AR-15 platform springs and mags. A conversion only requires replacing the barrel, bolt, and gas block to fire the 458 round. Many shooters simply have a dedicated upper receiver to quickly switch between 5.56 and 458 SOCOM.

The 458 has not received the widespread acceptance of other thumper rounds like the 450 Bushmaster, however 458 SOCOM enthusiasts love the ability to quickly switch between supersonic and subsonic rounds by simply changing mags. Hog hunters especially love the round for its power and fast follow-up shot capability when filling up their coffers with feral bacon.

As the 458 has been optimized for use with suppressors and in barrels as short as 9.5”, the SOCOM round offers shooters an extremely powerful cartridge that is ideal for both hunting as well as self-defense in their standard AR-15 rifles.

A Brief History of 5.56 NATO

After the Korean War, the U.S. Military started designing a new rifle cartridge for its frontline service rifles. And in 1954 the 308 Winchester (7.62x51mm NATO) was adopted to fill this role.

However, after early engagements in Vietnam, the U.S. Army wanted a new rifle that fired a lighter, intermediate cartridge like the AK-47. This would allow their soldiers to carry more ammo into battle while maintaining powerful terminal ballistics to remain combat effective.

This was the beginning of the 223 Remington.

Development of the 223 Rem rifle round began in 1957 and the final design was submitted by Remington Arms to the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) in 1962.

The development of the 223 Remington cartridge was a joint operation organized by the U.S. Continental Army Command between Fairchild Industries, Remington Arms, and Eugene Stoner of Armalite, using the 222 Remington as a parent cartridge.

The original 223 Rem mil-spec ammo that the U.S. Military adopted was named M193, which fired a 55 gr full metal jacket (FMJ) bullet at a muzzle velocity of 3260 FPS with a muzzle energy of 1294 foot-pounds.

The M193 cartridge served the U.S. Army all the way through Vietnam, however, FN Herstal changed the game in the several years later.

In 1980, the Belgian firearms and cartridge manufacturer Fabrique Nationale (FN) Herstal submitted their designs for the SS109 5.56x45mm cartridge to NATO for approval. The SS109 fires a 62-grain FMJ bullet with a mild steel penetrator tip at 3,110 fps and has a muzzle energy of 1,325 ft-lbs.

The U.S. Military designation for the 5.56mm NATO SS109 is the M855.

The new 5.56mm NATO cartridge had identical external dimensions to the 223 Remington, however the NATO cartridge can handle a higher maximum pressure.

Although, as with many things in life, sometimes the newer, shinier toy is not always the best.

The adoption of the SS109 NATO round has come under some criticism due to battlefield reports of the ineffectiveness of the 5.56’s stopping power, accuracy, and effective range. This has led to several advancements in 5.56mm NATO ammunition.

One of the biggest criticisms of the SS109 NATO cartridge was its inability to yaw (tumble) and fragment. The M193 was well known for tumbling and fragmenting upon entry into soft tissue, causing additional damage to the target.

The Mk 262 was the next iteration of the 5.56mm NATO round was one that fired a 77 gr OTM (open tip match) bullet designed for the Mk 12 SPR (squad precision rifle). Special Forces became fond of the MK 262 as it offered better terminal ballistics in the M4 carbines than what was observed with the SS109 NATO rounds. However, the Mk 262 was not adopted for widespread use due to the increased cost of heavier OTM bullets.

The Mk 318 was the next 5.56mm NATO cartridge evolution that used an open tip design to facilitate soft tissue damage and a solid brass penetrator base for added barrier penetration. This allows it to be employed against targets with or without body armor. Furthermore, the Mk 318 will fragment upon impact and is not dependent bullet yaw (tumbling) like the M193 and M855.

The most recent iteration of the 5.56mm NATO round is the M855A1 (ingenious naming, I know!) And the reason for its development is even more awe-inspiring to say the least.

The M855A1 was developed because the U.S. Military wanted to go “greener” and move away from lead-core bullets.

However, all environmental jokes aside, the M855A1 proved to have several distinct advantages over traditional M855 ammo. It was slightly more accurate, provided improved terminal ballistics and wounding capacity, as well as increased barrier penetration.

The M855A1 fires a 62 grain FMJ bullet with a solid copper core and steel penetrator tip extending past the jacket and has been in service since 2010.

To read more about the 5.56 NATO, check out the full history of the cartridge on our 5.56 NATO history page.

If you’d like to learn more about how the 5.56 compares to other calibers, check out these articles below:

• 308 vs 5.56
• 5.56 vs 223
• 300 Blackout vs 5.56
• 5.56 vs 7.62x39

Final Shots: 458 SOCOM vs 5.56

The 5.56 NATO is one of the most popular centerfire rounds in the world as it offers military, law enforcement, and civilian shooters a low-recoil cartridge with a flat trajectory and an effective range of around 500 yards.

However, the 5.56 is not without its shortcomings, as many combat veterans critique the round for its low stopping power as not being sufficient for modern combat situations.

The 458 SOCOM is one answer to this issue. With almost double the kinetic energy at the muzzle compared to the 5.56, the 458 SOCOM is extremely potent in short-range combat or hunting scenarios but lacks the long range capability of the 5.56.

Picking the right cartridge for your AR-15 rifle primarily depends on your intended use.

Most shooters will opt for the 5.56, as its low cost of ammunition and wide variety of rifles helps them spend more time on the range without breaking the bank.

However, if you want to hunt hogs or need a potent cartridge for home defense, then the 458 SOCOM is an excellent option for these applications.

Regardless of which cartridge you choose, make sure you get all your ammunition here at Ammo.com and get out to the range so you are always ready to defend freedom should the need arise.