Myths About the NATO 5.56 Cartridge

M16A1, M16A2, M4, M16A4

There are a lot of myths and misconceptions surrounding the current M16A1, M16A2, M4, M16A4NATO 5.56 round and its effectiveness on the battlefield. Now before you make a judgment as a soldier or as a firearm enthusiast (a more euphemistic way of saying “gun nut”), consider your sources. Who is it that is telling you the 5.56mm, or .223 if you prefer, is an ineffective round? Is this source an armchair general who has watched Blackhawk Down one too many times; or a Navy Corpsman who has been attached to a MEF fighting in Fallujah and has seen, treated and inflicted these wounds with his own M-4? People look at the .30-06 round from their grandfather’s M1 Garand and the 7.62×51mm round from their dad’s M-14 and compare it to the M-16/M-4’s 5.56 and think; “Wow, this is considerably smaller. Therefore, it must be less effective.”
Now Joe Nichols had it right when he said, “Size Matters.” However, when you are talking about combat cartridges this is not always the case, and I say that hesitantly. When the 5.56 was derived from Remington’s .223 in the late 1950’s, it was meant as a “force multiplier” if you will. By that I mean a soldier could literally carry twice as much ammunition as one who has the older 7.62 for the same weight. They wanted a soldier who could stay longer in the field without re-supply and could literally out-last and out-shoot the enemy in many aspects. The 5.56 is an incredibly fast and flat shooting round compared to the 7.62, but is under half the bullet weight.

So one might ask; ‘How in the world can a smaller bullet be more lethal than a bigger one?” One word: cavitation. Cavitation is the rapid formation and collapse of a substance or material after an object enters it at a relatively high velocity. I guarantee you have seen cavitation before. Next time you are in the pool or on the boat, look at your hand as it passes through the water or the propeller spinning. In both cases you will notice bubbles on the trailing edge of each. You see this because the liquid water falls below its vapor pressure. Without getting into physics and the hydrodynamics behind it, I’ll just leave it at that. When a human body is hit with a 5.56mm 62-grain bullet traveling at 3,100 feet per second; essentially the same thing happens but much, much more violently. For a split second, the cavity created inside the human body by the round from an M-16/M-4 is about the size of a basketball (if hit dead center of mass). The 5.56 creates this massive cavitation by tumbling through the body initiated by inherently unstable flight.

5.56 ballistic test
5.56 ballistic test

Other calibers of bullets travel through the body on, more or less of, a straight line after some fragmentation. When the 5.56 round was first designed by Remington, it was meant to tumble through a target, not kill with brute force. It did this not only by the relatively blunt shape, but also by using a rifle barrel with less of a twist. Next time you look at an M-4 or an AR-15, notice it says “5.56 NATO 1:7” on the barrel. This literally translates into; “the bullet will make 1 full rotation for every 7 inches of this barrel.” This was not always the standard twist set for the new NATO round. The first AR-15 made by Armalite, had a 1:14 twist making it a very, very unstable round. One can only imagine the orientation of the entry and exit wounds. Now if you haven’t figured it out already, the less the twist, the more unstable the round is. (1:14 twist is less than 1:7) It is said in “firearm enthusiast” legend that the first tests were done on pig carcasses and that the entry wound could be on the lower right stomach with an exit wound coming out of the back upper left shoulder. It left horrific wounds and terrible internal damage to its intended target, immediately drawing the interest of the US Military, in particular USAF General Curtis Emerson LeMay. That’s right folks, you can thank we in the United States Air Force for the M-16/M-4 legacy (I say this without sarcasm). He thought it was an ideal weapon for his deployed members of the USAF Security Forces for guarding the perimeters of Air Force installations in such places as Korea and Vietnam. Before military trials, Armalite increased the barrel twist to 1:12 to improve accuracy. But when tested in frigid Alaska, accuracy was decreased because of the increased friction from the denser, colder air. Therefore, the barrel twist was eventually increased from 1:12 to 1:9 and eventually to the 1:7 you see it today. Although some bull-barreled AR-15’s and Stoner Sniper Rifles can be found in a 1:9, most issued M-16’s and M-4;s are primarily a 1:7 twist.

This change increased the accuracy of the 5.56 round out past 500 meters, but decreased its lethality when striking a body. Now the real debate begins… How truly deadly is the 5.56? Well, this past April when I was going through Combat Skills Training at Ft. McCoy, Wisconsin, one week was spent in Combat Life-Saving class (CLS). The medics who instructed us had slide show after slide show of combat injuries they have treated over their last three deployments to Iraq and Afghanistan. And let me tell you, these were not for the weak stomachs among us. If you are reading this article, I bet you are the same type of person as I to ask, “What calibers caused those wounds?” These men and women have seen the worst injuries of coalition forces and enemy combatants alike. The Geneva Conventions state that medics must provide medical care to all captured enemy personnel when able. Therefore, many Taliban and Jihadist fighters came across their operating rooms. After class one day I asked all of them, “Do any of you doubt the killing power of the 5.56 round?” They all answered with a resounding, “NO.”
I personally don’t like telling war stories but I do enjoy telling hunting stories. I have brought down 180 to 200+ pound deer with a 55 grain .223 FMJ (full metal jacket) with no problem. Yes, I know, the counter argument to that is, “Well that’s not an enemy combatant hopped up on cocaine, khat or adrenaline.” I understand that, but if you saw the exit wound or those on the pictures from the combat medics, you would certainly cease your criticism of the 5.56. However, there are certain design features of the M-16/M-4 that continue to puzzle me.

We have all heard the reports of those rifles failing during combat during Vietnam and even yet today. During the 60’s when it was first introduced, it was hailed as “the self-cleaning rifle.” Of course that was proven to be a myth within the first months of its service. Soon thereafter, cleaning kits, cleaning manuals with attractive cartoon-like characters, and muzzle covers were issued in large numbers. A lot of the first problems the rifle saw were due to using ball powder vs. stick powder. Ball powder burns hotter, faster and dirtier than stick does. This caused the rifle to gum up quicker in the humid atmosphere of Vietnam and mis-feed the rounds. The U.S. Military then switched back to the cleaner burning stick powder and added a forward assist to jam the bolt carrier forward after heat expansion and carbon build-up. The military saw this problem and fixed it fairly early on, so why haven’t they saw the clear flaw in the 100% gas-blowback operation of the firearm? Why haven’t they learned lessons from rifles such as the AK-47, AK-74, G36, SCAR and countless other who have switched to a short stroke gas piston?

gas piston operated
gas piston operated

So far rifles such as the HK 416, HK 417, SCAR and MAGPUL Masada have all incorporated this short stroke gas piston in their designs and have all seen massive reductions in carbon build-up, over-heating, and mis-feeds. If this needs any explaining; what this basically does is stop the hot, carbon-filled gasses just rear of the front sight and pushes a pistol-like rod back instead of the gas traveling all the way back to the bolt carrier assembly. It is even possible to convert current uppers to this gas piston system using such kits as those offered by Bushmaster. If the cost benefit is too great for these kits to be installed, why not begin to install them on the floor as they are now? They are 100% compatible with all lowers used by the M-16 and M-4.

So in conclusion, the main flaws of the M-16/M-4 assault rifle system is not necessarily in the round itself, but in one minor design feature of just the upper. This article is meant as a predecessor to a piece in the making on the advantages to switching to a round such as the 6.8 SPC or 6.5 Grendel. The 5.56 round is effective, but could be better. I want to hear your feedback. Tell me why so many people (mostly civilians) think the flaws of the rifle are in the round. I’m looking to you military folks; tell me about your operational experience with it. Airsoft players, armchair generals, and firearm enthusiasts; let’s hear your voice, but don’t comment on its “knock-down power” unless you hunt big game with a .223 or were once in the military and have used it in combat. Next up: A viable future replacement for the 5.56 and the M-16/M-4 combat rifles along with first-hand news from the front on forces already making the switch.

Remember; every rifle and every round can be equally as deadly when put in the right hands. We seek to find the perfect round and the perfect rifle to increase that number of hands.

3 thoughts on “Myths About the NATO 5.56 Cartridge”

  1. I believe the answer to those statements are the fact that the short-stroke piston doesn’t fix the problem enough. Simple maintenance is enough the keep the M4’s going. So they figured, “Why pay $2000 more for something that can be fixed with lube?” I bet they felt that it was too expensive for not a lot of benefit.

  2. Also, we use stick-powder now. The piston doesn’t determine “knock-down power”, the bullet size and powder does.

  3. Gas fed doesn’t increase power it reduces heat expansion, carbon buildup and round misfeeds, ie. jamming, probably related to the first 2 issues, he never said gas piston increases stopping power, its for efficiency

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