Is There a Problem with the Lethality of the 5.56 NATO Caliber?
To answer this question with a short answer, it is: No! This article will discuss the benefits of the 5.56mm NATO caliber, compare it with its bigger brother 7.62, look into effects of barrel length and finally how to improve the lethality of our soldiers.
First, there are two ways to incapacitate an enemy:
- Hit to the central nervous system. This is the brain and upper part of the spine. It will cause immediate incapacitation regardless of caliber or type of bullet.
- Loss of blood pressure by massive bleeding. This area corresponds to the rest of the central body and incapacitation can take time. Hunters aim for the lungs and heart when they hunt. A deer shot right through the heart can run quite some distance.
Soldiers are top priority within NATO and the soldier’s primary weapon is his rifle. To use it effectively he must be well trained for any possible encounter with the enemy and it is very important that he “trains as he fights.” In his final training there must be pop up and moving targets at unknown distances. He must be under stress and be able to respond immediately. There has been small arms lethality discussions within NATO for several years, but to clarify things once and for all a NATO Workshop on Small Arms Lethality was hosted by the United Kingdom in February 2009 at their Defence Academy in Shrivenham. The conclusion was that shot placement is the most important parameter, and that this is achieved through good and realistic training.
There are two major problems with current and future soldier systems: weight and power supply. Individual soldiers can in operations carry 60 kg (132 lbs). This includes weapon, ammo, body armor, water, etc. Many nations try to lighten soldiers load incrementally by trying for each new procurement to lighten each new item by a certain percentage over the one it is replacing. Most accessories use batteries. These are often of different size and have different life expectancy. NATO is currently studying several industry solutions of a powered rail system, where the power is centralized in the pistol grip or buttstock and is sent to the rails where the flashlight, as an example, then would only consist of a reflector, which reduces weight and volume of the device and increases battery life expectancy.
The Belgian small arms producer FN Herstal – then named FN (Fabrique Nationale d’Armes de Guerre) developed a weapon family in the mid 70s consisting of the FNC rifle and the Minimi LMG (light machine gun). To increase the range for the LMG, a round that could penetrate the NATO plate (3.5mm mild steel) out to 600m was developed. It had a dual core (steel tip and lead rear), and was designated SS109 and required a one in nine inch rifling twist. There were no requirements to penetrate body armor. The L110 tracer round however required a fast one in seven inch rifling twist.
In 1970, NATO decided to try to standardize a common rifle and a second rifle caliber. During 1977-1980 NATO therefore performed tests with rifles and ammunition. The calibers tested were:
- 5.56mm rounds with increased penetration from Belgium (FN SS109) and USA (XM777).
- A British 4.85mm round. This was a necked down 5.56mm cartridge.
- A German 4.7mm caseless round.
The results were that no weapon could be agreed upon as many of the weapons were prototypes. The SS109 round was found to be the best, and was standardized as NATO’s second rifle caliber in 1980.
One quite often reads and hears of the benefits of 7.62mm over 5.56mm. The truth is, however, most of the time the opposite. The benefits of 5.56mm over 7.62mm are:
- Equal lethality against unprotected enemies.
- Half the mass (12g – 24g).
- Half the volume.
- Reduced recoil and signature (noise and flash) that allows for a faster second shot.
- Better penetration in thin metal plates.
- Flatter trajectory and shorter time of flight out to 700m.
- Lighter weapons.
- Higher hit probability.
The last bullet point refers to that the soldier is not afraid of the recoil and noise, and can concentrate on his stance, weapon control, aiming and trigger pull. Several nations have reported this when they changed from 7.62mm caliber to 5.56mm.
The benefit of 7.62mm is that it has more energy. The impact energy of the 7.62mm is more than twice of the 5.56. Energy is only needed if you want o penetrate body armor or RHA (rolled homogeneous armor). If the target is not protected, that energy level is not really needed. A 5.56mm or 7.62mm ball round will normally pass right through an enemy all the way out to over 600m.
NATO realizes that different nations spend a different amount of time, ammunition for training and expect soldiers to perform to different levels of marksmanship. This resulted in Spain hosting a NATO Workshop on Marksmanship Training March. The results showed that only few nations teach shooting to ordinary infantry soldiers beyond 200-300m. Nations are using from 150 rounds during 28h engaging targets out to 200m and up to 1,000 rounds during two weeks engaging targets out to 400m. The soldiers are thereafter sent on missions to, for example, Afghanistan. Sweden and Canada both share the common requirement that a soldier in the prone or kneeling position must be able to put 3 (Sweden) or 5 (Canada) rounds at 100m with maximum dispersion of 150mm (6 inches).
The reasons nations do not teach their soldiers to shoot at longer range are that it is very difficult to hit at longer range due to:
- Shooters dispersion
- Moving targets
- Unknown range
- Wind drift
Swedish units in ISAF rely on 12.7mm HMG for long range.
Let us look at a comparison between 5.56mm and 7.62mm with equal barrel lengths (20-inches – 508 mm):
As can be seen, 5.56mm has a flatter trajectory. So now let us compare a 5.56mm M4 barrel (14.5 inches) with a 7.62mm long barrel (20 inches). They are identical. There has been some debate that the “short” M4 barrel is the cause of some “lack of lethality” issues. This is simply not true. The same thing applies to time of flight for these. This is an important issue because it affects the required target lead when engaging moving targets.
In the Swedish ak 5 upgrade trials in the early 2000s the users were asked to prioritize the suggested changes. Priority 1 was the rail on the top of the receiver and priority 2 was the shortened barrel. Soldiers really loved the short compact ak 5C. There is no measurable difference in the accuracy of a 450 mm and 350 mm barrel.
Let us look at some interior ballistics. With caliber 7.62 the barrel is typically around 20 inches (508mm). The bullet will have 50% of its velocity within 80mm (3 inches) of travel. If you shorten the barrel you will lose some muzzle velocity, and you will increase the muzzle pressure (noise and flash).
To scientifically investigate the effect of barrel length and muzzle velocity we took a brand new Colt M16A2 barrel and cut it down in 30mm increments and measured the velocity. We used NATO reference ammunition, fired at +21° C.
The effect of a long barrel has often been greatly exaggerated. The trajectories for the M16 (20-inch barrel) and M4 (14.5-inch barrel) resulted in a difference of only 16 mm (0.6 inch) when zeroed at 250m.
It has also been stated that the striking velocity from the M4 carbine was very low because of its “short” barrel. The fact is that there is only a 50m difference. Do you think an enemy will notice being hit by a M16 at 200m or a M4 at 150m?
The difference in time of flight is also very low, only 2 cm (0.75 inch) per meter per second of traverse target movement at 300m. An enemy normally walks at 2m/s and runs at 5m/s.
Back in 2005 I attended a NATO group and we were discussing what were the reasons soldiers did not hit their targets. I had previously done a study with 7.62mm caliber and was asked to do the same with 5.56mm. I received input data from the participating nations. I took the most important data and created two different scenarios:
- Kneeling, no stress.
- Standing, stress.
The lessons learned is that the latter should go down into the kneeling position, which will increase his hit probability and reduce his target area.
It is easy on the Internet to find rumors about the “lack of lethality” of the 5.56 NATO round:
- “Ineffectiveness at long range”
- “Inconsistent wounding effect”
- “Poor intermediate barrier penetration”
- “Ease of deflection”
The fact is that there are no official documents that the 5.56mm NATO caliber has failed in any NATO Army. On the contrary, we have official documents stating that there is no problem with the lethality of the 5.56mm caliber at all. Most NATO nations even agree that the next generation of small arms weapons by 2020 will still be using the 5.56mm NATO caliber.
- There is no problem with the lethality of the 5.56 NATO caliber.
- Most NATO nations are confident with the lethality of their 5.56mm and 7.62mm rounds.
- To increase small arms lethality, nations must better train their soldiers.
- Soldiers must “train as they fight.”
- If nations want to engage targets at long range, then it is not about rifle caliber, projectile or barrel length, it is all about more training.
Terms of Reference for the NATO Weapons & Sensors Working Group
- The group is responsible for all issues related to dismountable soldier’s weapon systems, non-lethal systems, grenades and shoulder launched and guided anti-tank weapons, as well as dedicated sensors (including, but not limited to day and night sights, laser designators, tactical lights and fire control systems).
- The weapon system includes the weapon itself, different types of ammunition and the dedicated accessories.
- The group is also responsible for the interface of the weapons and sensors with the various other parts of the soldier system.
About the Author
Per Arvidsson is a former military officer, has a Master degree in weapon technology and ballistics from the Swedish military academy, worked with small arms systems at FMV (the technical and procuring agency for the Swedish armed forces) for nearly 30 years, has been the product manager for small arms systems since 1994, has been active in various NATO groups since 1998 and was elected chairman for the Weapons & Sensors Working Group in 2008.