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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.

 

 

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.

There’s a lot of data at the source.

Recall when we speculated about why the ATF had decided to hold its “green tip” ban in abatement?  Well, the questions are answered.

The Bureau of Alcohol, Tobacco, Firearms and Explosives on Thursday raised new concerns about surplus military ammo used in popular AR-15 rifles and pistols just days after pulling back on a proposal to ban the ammo because it could threaten police safety.

In a Senate Appropriations Committee hearing, ATF Director B. Todd Jones said all types of the 5.56 military-style ammo used by shooters pose a threat to police as more people buy the AR-15-style pistols.

“Any 5.56 round” is “a challenge for officer safety,” he said. Jones asked lawmakers to help in a review of a 1986 bill written to protect police from so-called “cop killer” rounds that largely exempted rifle ammo like the 5.56 because it has been used by target shooters, not criminals.

His agency’s move to ban the 5.56 M855 version was condemned by the National Rifle Association and majorities in the House and Senate and as a result was pulled back though not abandoned. At the hearing Jones said that nearly 90,000 comments on the proposal were received, many negative.

As a result, he said that the ATF will suspend rewriting the “framework” used to exempt armor piercing ammo from sale or use. “It probably isn’t going to happen any time soon,” he said. Jones also said, “We are not going to move forward.”

The 5.56 M855 round, he said, is military surplus, typically has a green tip and was used in the M-16. There are several versions of the 5.56. The M855carries a bullet that can penetrate police body armor, though shooters often debate that.

The ATF singled it out for a ban because more AR-15 style pistols that can shoot the ammo are being produced and presumably could be used by criminals in police shootouts. The AR-15 can also shoot the less lethal .223 round, which was not targeted by ATF in the ban proposal.

My God, this is one messy article.  There are too many confused issues to sort through in a short amount of time, but I’ll mention just a few.  The 5.56 mm cartridge and the .223 cartridge are very similar but not identical, with chamber leade being the main difference.  There isn’t enough of a difference to distinguish between 5.56 mm and .223 for purposes of this article.  This would be of interest in the gun community for things like slight differences in muzzle velocity, chambering, shooting a cartridge in a gun specified for another, etc.  Presumably, the author of the article inserted this confusion and not Mr. Jones.

But Mr. Jones did indeed insert obfuscation and confusion, and then asked the Congress to use that confusion to add to the regulatory and legal burden placed on citizens.  There is no reason to debate the issue of green tip, despite the URLs the author inserted into the article.  As I’ve explained:

Common 5.56 mm ammunition will penetrate soft body armor, all of it, period.  Kevlar will not stop 5.56 mm ammunition (lead ball) shot at 3200 FPS.  Nor will soft body armor stop most rifle rounds.  Soft body armor is [routinely] tested for 9mm pistol ammunition, not rifle ammunition.

ESAPI (enhanced SAPI plates, or the ceramic ballistic plates worn in ballistic plate carriers) are designed to stop rifle rounds, and are specifically tested for M855.  No cop today (or anyone else for that matter) wearing Kevlar is protected from any rifle round (unless it is from something like a pistol caliber rifle), and the existence of M855 or lack thereof doesn’t change that.  Likewise, a cop (or anyone else) wearing ESAPI plates is protected from rifle rounds, including the M855, and the existence of the M855 round or lack thereof doesn’t change that.  Finally, even ESAPI plates must stop a certain percentage of rounds (so there is some probability of fracture and penetration even with tested and specified rounds regardless of type).

So you understand, don’t you, that the M855 ban has absolutely nothing whatsoever to do with LEO safety, the liar in the White House notwithstanding?

Banning green tip does nothing to prevent anyone from using a rifle round (shot from any weapon) to penetrate soft body armor, and wearing ceramic ESAPI plates protects against both frangible 5.56 mm ammunition and green tip ammunition.  Furthermore, a so-called 5.56 mm “pistol” is nothing more than a SBR (short barrel rifle) with a barrel length of less than 16″ and no stock.  It isn’t concealable.

So speculation of course ran wild as to the exact intent of the ATF.  Are they stupid?  Do they not really understand the technical issues they are dealing with?  But today B. Todd Jones answered those questions.  They are concerned about all 5.56 mm cartridges.  Of course they are.  But that .270 pointed soft point, shot from a necked down 30-06 cartridge from my bolt action deer hunting rifle?  Yes, that’s the one.  It will penetrate soft body armor too – lead ball, soft point, all of it.  So will lead ball 30-06.  So will lead ball .308.  So will lead ball 7 mm.  Virtually all rifle rounds (except .22LR and .22 WMR) will penetrate soft body armor because kevlar is specified to 9 mm rounds (as regards mass and velocity).

Jones knows that.  The ATF at large knows that.  What Jones is telling the Congress is that he wants their help in banning rifle ammunition.  Rifle ammunition.  All of it.  They will start with 5.56 mm ammunition, green tip, lead ball, pointed soft point – all of it.  Then they will make it clear that all other rifle ammunition is as lethal as 5.56 mm ammunition, so they need a ban on that too.

Here’s a warning flag to all the Elmer Fudds out there who only care about your bolt action hunting rifles, and think this stuff about AR-15s is all just a bunch of made up theater to bother pampered folk like you.  They want your rifles and ammunition too.  You do understand that, don’t you?

Janes:

Thales Australia has disclosed it is developing a new family of high-lethality small arms ammunition, including a 5.56 mm round that the company says outperforms 7.62 mm ammunition at all ranges.

The so-called F9 technology is scalable in calibre, from 4.6 mm up to .50 calibre, and is being developed in collaboration with an undisclosed overseas partner, Graham Evenden, Thales Australia’s Director of Integrated Soldier Systems, told IHS Jane’s on 20 August.

The initial focus is on 5.56 mm ammunition. Trial batches use a projectile developed by the overseas company, low toxicity, optimised propellant from the Thales-operated Mulwala propellant and explosives plant in southern New South Wales, and cases produced at the Thales-owned Benalla munitions facility in northern Victoria.

The design of the 5.56 round involves yawing in flight (even for boat tail ammunition) such that impact tends to fragment the round leaving multiple ballistic tracks through tissue.  UPDATE: This is a correct and functioning link to the paper entitled Small Caliber Lethality: 5.56 mm Performance In Close Quarter Battle.  Warning, this is a PDF supporter by a very slow server.

Color me unpersuaded until I see test results.  But I’m interested, if someone from Thales Australia wants to contact me and give me more detail.