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The Truth About M855 5.56 NATO Ammunition

IMI Systems 5.56 ammo (courtesy thetruthaboutguns.com)
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The [Obama] White House has said that banning “armor piercing” ammunition like the wildly popular M855 round is “common sense” and would make our police officers safer, which is a bold claim. Given the quality of journalism on display among the major networks these days, it’s no surprise that the facts of the matter have been muddled and obfuscated to the point where the details being presented bear little to no resemblance to the actual facts . . .

Some hyperbole is expected, but in an age when the talking heads on TV start claiming that common rifles can shoot down airplanes and blow up railroads you know that fact checking isn’t high on the priority list. I wanted to take a minute and discuss the truth about the M855 round, what it is, what it does, and why it is being targeted.

When the M-16 was first fielded by the U.S. military, the ammunition that accompanied it was designated the M193 cartridge — a standard brass case “ball” full-metal-jacket (FMJ) 5.56 round. The 55-grain FMJ projectile was of the same construction that had been used in similar projectiles for close to a century, namely a solid lead core surrounded by a copper jacket.

The original mil-spec parameters for the M-16 rifle were that it needed to penetrate the steel helmet of an enemy soldier at a given distance, and while the lighter overall weight of the projectile reduced the penetration power of the projectile at long distance, the designers of the ammunition compensated with increased muzzle velocity. Increased velocity meant increased muzzle energy, and provided the power to meet the specifications.

That faster-fps yet lighter bullet meant that the cartridges were lighter, and therefore the soldier on the field could carry more ammunition into battle than ever before. Even with the lighter projectile, that “armor piercing” capability was still maintained throughout the design process.

After the Vietnam war, there were some deficiencies that needed to be addressed. Soldiers in the field reported issues with the projectile when it penetrated glass or other intermediate barriers, and wanted a heavier projectile to aid in energy transfer to targets downrange (putting down enemy soldiers more efficiently).

While the military did adopt a 77-grain lead projectile for long range shooting, they developed the M855 projectile specifically for hitting targets behind light barriers (like glass and tin and heavy clothing).

The internal construction of M855 green-tip ammo differs from the standard “ball” M193 cartridge in one very important way: there’s a steel core at the tip of the projectile. The solid-steel penetrator added much needed stability to the projectile when traveling through barriers since there was no longer any soft lead to deform upon impact, and increased the stability and accuracy of the round when traveling over long distances due to the increased mass of the projectile.

There were still some major issues, though. As the barrel length of commonly used firearms continued to decrease, the velocity of the round when it exited the barrel decreased as well. The 5.56 NATO cartridge is highly dependent on velocity to generate the energy it transfers to targets, and lower velocity means a much lower muzzle energy.

Some of the most recent studies indicate that with a common 16″ barrel in an AR carbine, M855 ammo has severely degraded performance past 150 yards and is only effective to about 500 meters (versus the 600 meters at which it was designed to penetrate a steel helmet with a standard M-16).

Another issue was the lack of expansion. The lead core in normal “ball” ammunition expands upon impact, which increases the diameter of the projectile and aids in transferring energy from the moving projectile to the target. The more energy is transferred, the greater the wound in the target and the more likely it is to stop that target.

Using a steel tip meant that the bullets no longer deformed, and therefore the energy transferred to the target was less than with 55 gr FMJ “ball” 5.56. In other words, the M855 ammunition is actually considered to be less effective against living targets than “ball” 55-grain bullet weight 5.56 NATO ammo. Or, put another way, standard lead ammunition rifle ammo is considered more deadly than M855.

While the Army has moved on to an improved version of the M855 military round, the cartridge has become popular with long range shooters and hunters. Especially for those hunting hogs in the thick brush of the American south, the M855 cartridge has proven to be capable of accurately and effectively hitting a target even after passing through a couple layers of leaves and underbrush.

It’s also popular among helicopter hog depredation expeditions for the same reason: it punches through the trees and hits the target. And since the cartridge was developed and produced as a military round, a massive quantity of the ammunition is produced every year, which leads to low prices for recreational shooters looking for a cheap way to feed their firearms. In short, what was once a “military” round has transitioned very well to civilian life.

In recent days, the projectile has come under increased scrutiny as the ATF prepares to ban it based on the existing prohibition on “Armor Piercing” ammunition. As for what exactly constitutes “armor piercing” ammunition, there is a very specific .gov legal definition that is being used. The following is directly from 18 U.S. Code § 921:

(17)
(A) The term “ammunition” means ammunition or cartridge cases, primers, bullets, or propellent powder designed for use in any firearm.
(B) The term “armor piercing ammunition” means—
(i) a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium; or
(ii) a full jacketed projectile larger than .22 caliber designed and intended for use in a handgun and whose jacket has a weight of more than 25 percent of the total weight of the projectile.
(C) The term “armor piercing ammunition” does not include shotgun shot required by Federal or State environmental or game regulations for hunting purposes, a frangible projectile designed for target shooting, a projectile which the Attorney General finds is primarily intended to be used for sporting purposes, or any other projectile or projectile core which the Attorney General finds is intended to be used for industrial purposes, including a charge used in an oil and gas well perforating device.

What is important to note is that the defining feature of “armor piercing” ammunition is not the actual function of the projectile, but instead the construction. It is possible to construct a cartridge using an “armor piercing” projectile that can’t even pierce skin, but if the construction meets the above criteria then it is illegal.

What has made this change in regulation possible is the prevalence of the AR-15 pistol. Brought to astounding levels of popularity in recent years by the pistol stabilizing brace, the AR-15 pistol is legally a handgun as far as the U.S. government is concerned, and therefore 5.56 ammunition has become by default a “projectile […] which may be used in a handgun.” As such, 5.56 NATO ammunition is now subject to regulation under 18 U.S. Code § 921(17)(B).

Technically, M855 ammunition fails to meet the criteria for an “armor piercing” projectile. The requirement of the law is that the projectile be comprised entirely of steel (with trace elements allowed) in order to be classified as “armor piercing,” but as you can see nearly 80% of the mass of the M855 projectile is comprised of standard lead — not steel. However, due to the imprecise wording of the statute it is possible for the ATF and the Attorney General to interpret the law in such a way that M855 meets the required criteria.

This kind of move has been made before. The government classified cheap and commonly available steel core 7.62×39 ammunition as “armor piercing” and banned it from the United States in 1992, as well as 7N6 5.45×39 ammunition only last year. The reasons were the same: with the increase in pistol versions of the AK-47 and AK-74 rifle being produced, this great ammo was now technically a handgun caliber and the broad interpretation of the statute allowed them to take action against those specific projectiles.

The current claim by the White House that M855 ammunition is especially and specifically dangerous due to its “armor piercing” capabilities is, in a word, laughable. The fact is that standard 5.56 ammunition — “ball” ammunition with a traditional lead core — can pierce “bullet proof” body armor just as easily as M855, a fact we have conclusively proven through our own testing.

So can commonly available .308 Winchester ammunition, one of the most popular “hunting” cartridges in the world. So can .30-06 Springfield, the “traditional” hunting cartridge in the United States. In fact, almost every full-size and even every intermediate rifle caliber is perfectly capable of piercing the bullet proof vest worn by police officers. The idea that removing this one single projectile from circulation will reduce the lethality of firearms in the United States is quite literally insane.

Let’s look at this from another perspective. According to commonly accepted research, fewer than 2% of crimes are committed with “assault weapons,” including the AR-15 rifle (and pistol variants) that accept this caliber. Note that the most commonly available 5.56 ammunition is 55 grain “ball” ammo and not M855, so even if every single one of those crimes was committed with an AR-15 (which they were not), the probability of M855 ammunition being used in the gun is even smaller than 2%.

Even if M855 ammunition was banned, standard “ball” M193 ammunition fails to meet the definition of an “armor piercing” round and therefore is exempt from any possible ban. M193 is plentiful, and available at almost every Walmart in America. Removing M855 ammunition would require a vast amount of effort on the part of the government to implement the ban, impact less than 2% of crimes, and do exactly nothing to remove ammunition that is capable of piercing a “bullet proof” vest from the market. In short, you might as well call whoever is championing this ban “Sisyphus.”

The truth is that, despite the composition of the projectile, M855 ammunition is no greater a threat than any other standard “ball” projectile — traditional hunting rounds in the normal 20-round box included. According to law enforcement sources, the 5.56 cartridge has been implicated in far fewer than 2% of crimes in the United States (and M855 in fewer still), and even if it were removed from circulation, the remaining millions upon millions of 100% legal projectiles would be able to perform the same function nearly as well.

In addition, the projectile has found a legitimate sporting purpose as a great value among hunters and sportsmen that the Attorney General has refused to acknowledge. However, due to the lack of any movement on any other front on the issue of gun control, it appears that M855 ammunition has become an unfortunate casualty of a political agenda hell-bent on doing as much damage to American gun owners as possible before leaving office.

Check out other TTAG coverage of 5.56 NATO/.223 Remington ammunition by clicking the links below: 

Ammunition Review: Allegiance Ammo Silent Strike Frangible Subsonic .223 Rem (5.56 NATO round)

5.56 NATO vs. 300 AAC Blackout Ballistics (cites Hornady data extensively for ballistic comparisons)

Looking to fill your ammo can with a good deal?

Brownells Now Selling 5.56 and 7.62×51 Ammunition By the Barrel (bulk ammo sales of Lake City Ammunition Plant rounds at a great price.)

First-time visitors might want to click here to see abbreviations of common bullet terms, such as HP (hollow point), BT (boat tail), FMJ (full metal jacket), FMJBT (combination form of full metal jacket boat tail), JHP (jacketed hollow point), and others. 

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