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M16 assault rifle

Written by Sakhal

The M16 was initially produced as a private initiative of the company Armalite. Lightweight, manageable and practically without any recoil, it was effective at real combat distances. Since then it has been the ordnance rifle of the United States Army and has been sold in millions around the world, even if the beginning of its military life was plagued with problems.

Unlike most weapons of this type, the M16 has its origin in a commercial project. Devised by Eugene Stoner, it was initially produced by the company Armalite as the AR-10, model consolidated during the second half of the 1950s. This weapon fired ammunition of caliber 7.62 millimeters, but following the apparition of the 5.56-millimeter Fireball cartridge it was reconverted to the new caliber, giving origin to the AR-15. One of the first important users of this rifle was the British Army, which acquired 10000 exemplars shortly before the US Air Force effectuated a similar purchase. This happened in 1961. When the AR-15 was chosen as the ordnance rifle for the US Army the production was transferred to the Colt Firearms Company, which obtained from Armalite a contract for production and sales. The M16A1 appeared in 1966 as a consequence of the very negative experiences with the original AR-15 in Vietnam. Colt produced as well a carbine version for special forces, known as Colt Commando, which was tested in Vietnam with not very satisfying results. Other models include a submachine gun variant and a support rifle with heavy cannon and bipod.

M16 assault rifle

The M16 has been seen as the western equivalent of the Soviet AK-47 and its derivatives, for it has been produced in several millions of exemplars and delivered or sold to numerous countries in the world. Countries such as South Korea, Philippines and Singapur have acquired the production license. The M16 is used as well as a policial weapon and can be acquired commercially in many countries. Despite of the many years in service, the M16A1 keeps the same appearance than the AR-15, albeit some modifications have been made, such as the new rifling on the bore and a greater utilization of internal chrome plated to ease cleaning. A more recent introduction was the M16A2, which has a heavier cannon and can be used with the new SS109 5.56-millimeter NATO cartridge, which required a new change in the rifling. The M16 operates by direct gas intake and uses the almost universally adopted system of breech closure by rotating bolt. Albeit studied for serial production, the M16 does not have the appearance of "tinfoil" of many contemporary weapons and possesses the finish of a high quality weapon. Perhaps the only shortcoming of the design is that the buttstock does not allow to be folded. This detail was taken into account in the subsequent model AR-18, but this weapon did not enjoy the same success than its predecessor.

The M16 in Vietnam

In the late 1950s the standard rifle in the US Army was the M14, a heavy (5.1 kilograms) and awkward weapon that fired the cartridge 7.62 x 51 and used the same basic operating system than the Garand M1 from the Second World War. Overall, it was a valid weapon that covered the requirements of a war in Europe and in many other places of the world, but totally inadequate for the short distances that are characteristic of jungle combat, to which the Americans were starting to be dragged with increasing frequency. When the French and the British withdrew from the Far East they left a political void that United States promptly proceeded to fill in the name of its national interests. And beyond the normal economic help, from the very beginning it was evident the North American military presence. Many of the Far East nations still used weapons from the Second World War and the Americans usually offered to replace those relics with new armament. However in the field of rifles the North American offer was not very suitable for the particular requirements. For the population of that region, commonly of low stature, rifles such as the M14 or the old M1 were clearly too bulky for being used with ease. Hence the Americans had to investigate on a new rifle adapted to such circumstances.

The weapon was soon found in the Armalite AR-15, a lightweight and compact rifle of modern appearance, which was practically devoid of any recoil when firing. A large amount of these rifles was acquired to be distributed among the diverse nations. But the instructors sent to the region, after noticing the advantageous characteristics of the AR-15, questioned whether it was wise to distribute so generously a rifle which was in many aspects superior to the ordnance rifle of the US Army. Their opinions soon reached the highest military hierarchies, which decided to get to the bottom of the question. In 1958, to replace the M14 with the AR-15 would have posed a drastic change in the supply of ammunitions and, as time demonstrated, that was the crucial point of the problem. But in 1961 the AR-15 - with the military designation M16 - made its official entry into the United States Armed Forces. Firstly the Air Force acquired a lot and then the Army started the distribution among the special units, this is, those which had more chances to get involved in the military activities in Southeast Asia.

For the Americans, that region started to become synomym of Vietnam. The number of units sent to the zone grew progressively until reaching a considerable proportion of the Army, and not much time would pass until they had to intervene in operations at large scale, together with their temporary allies. Among these forces it had been distributed with priority the M16, but soon arrived to the Command the first complains about the unsatisfying behavior of the new weapon. It jammed with extreme ease and suffered constant obstructions and breakings. Two independent commissions were constituted for inquiries, one in charge of the Army and the other in charge of the Congress. This latter faced the problem with greater energy and determination, and promply brought to light a unedifying story. The fist tests effectuated by the US Army had given satisfying results and the later distribution of the rifle to the troops had been accompanied with a statement from the manufacturer that such an efficient weapon would not require cleaning or maintenance. It is not clear how such a misconcept could make its way to the operation manuals, but in those days the soldiers took it as true with joy, and never cared to clean their rifles. It seems incredible that a rich and powerful nation as United States could fall in such extreme inefficiency.

The largest part of the obstructions and breakings were caused by the lack of maintenance but there was still an even more inconceivable reason: the specification of the ammunition had been changed without prior notice. For the initial trials of the AR-15 it had been used commercial ammunition which used as propellant charge that known as IMR (Improved Military Rifle), which had been used for big game during many years. When it was fired on the 5.56-millimeter cartridge it burned cleanly and without problem. This kind of powder was used in the first service lots, but the subsequent lots were delivered with a new propellant, known as granulated powder and which had been introduced for general utilization in 1954. The absurd practice of not cleaning the rifle, combined with the residues left by the 5.56-millimeter cartridges filled with the new propellant, gave as result the solidification of cinder and other residues which ended jamming the mechanisms of the M16, specially the head of the bolt. And to put things further bad, for the soldier in campaign it was impossible to fix the problem once it started, for the rifle lacked any cocking lever. The only way of unblocking the rifle was to introduce a ramrod or a similar instrument through the bore. Legion became the stories of soldiers jumping from position to position asking their comrades for help, and numerous casualties happened while unblocking the jammed rifles during combat. And if this was not enough, the mobile mechanical parts overheated by excessive friction often broke.

In that time, the mid 1960s, the Government decided to release the military from the ongoing investigation. Many of the civilians belonging to the comission of the Congress were ex-military who had made puzzling discoveries. They found rifles covered with dirt and rust and even exemplars completely obstructed and blocked by the incrustations. And they soon discovered the change in the ammunition. As soon as things became clear it was started an accelerated program for instruction on cleaning and maintenance, being distributed the necessary tools and lubricants. The soldiers started to take care of the cleaning of their M16 and the situation instantly improved. Besides, a modification was made in the production lines: in the right side, next to the trigger group, it was added a manual device which, in the event of a jam in the breechblock, would allow to force a cartridge into the breech. After this modification the rifle received the denomination M16A1 and became a perfectly reliable assault rifle. Well, with the exception of unusually dusty and sandy places, such as Middle East. The numerous exercises carried out by the Rapid Deployment Force in Egypt and other places confirmed the existence of this problem, which required a new series of cleaning procedures for being solved.

In spite of all these difficulties the M16A1 has demonstrated to be a valid war weapon. The only critic of many military experts refers to its ammunition, for in general terms the bullet is considerably less powerful than a similar projectile of larger caliber. Only if at the moment of impact the bullet "overturns" the shock effect on the wound could be comparably serious. To some extent these deficiencies were solved with the introduction of the new Belgian cartridge SS109. Nowadays the M16 constitutes the ordnance individual weapon adopted by numerous armies in the Far East and South East Asia and some of these countries even started to produce it only for selling it to their neighbors.

Anatomy of the M16

With a length of 990 millimeters, the M16 is not particularly compact in comparison with other assault rifles. This condition is aggravated by the fact that the buttstock cannot be removed or folded because it contains the return spring. However it is a really lightweight weapon, with a weight of 3.64 kilograms when loaded with a 30-round magazine. This was partly achieved by using plastic instead of wood on the handguard, pistol grip and buttstock. It is a gas-operated weapon; this means that the bolt remains locked until a minor portion of the gas generated by the cartridge is returned to the breechblock slide to continue the firing cycle, of 700-950 rounds per minute. The gas intake, located just below the fore sight, gives access to a narrow gas duct which lacks any piston, so the gas actuates directly on the breechblock slide; this feature allowed to save weight as well. The problems with jammings in Vietnam started precisely in the gas intake, passing then to the breechblock through the gas duct. The breechblock slide operates with a bolt which locks into the breech by rotation; it is a delicate mechanism, for any grain of dirt could be enough to block it. The barrel has a length of 508 millimeters and was originally topped by a flash suppressor that allowed as well to adapt a muzzle grenade launcher; however nowadays the grenade launcher which usually accompanies the M16 is the underbarrel model M203. The 5.56-millimeter bullets leave the muzzle with a speed of 1000 meters/second, granting an effective range of 400 meters. A selector placed just above the pistol grip allows to fire in either semiautomatic or automatic mode, or to put the weapon in safety mode. The ammunition is fed by metallic or plastic magazines containing 20 or 30 rounds. The fore gunsight consists of a pin protected by two very pronounced side structures, while the rear sight, adjustable for 300-500 meters, is contained within the carrying handle.

M16 assault rifle

The M203 grenade launcher

The North American series of 40-millimeter grenades was originally developed to fill the gap existing between the smaller series of mortar grenades and the hand grenades. The family, of which dozens of types exist, is generally known as M406, whose members resemble large and stumpy bullets. The firing system allows the propellant gases to escape through a number of holes in the breech, giving as result a shot of relatively low pressure and allowing to fire these grenades from rather light weapons. The M203 underbarrel grenade launcher, a well known companion of the M16 during decades, was developed in the late 1960s to allow a rifleman to transport his own grenade launcher and to fire his rifle independently of having a grenade launcher attached to it. The launcher, of 380 millimeters in length, weighs only 1.36 kilograms (or 1.63 kilograms when loaded) and it is a single-shot weapon. By sliding the barrel forward a new grenade can be introduced onto the breech and by sliding the barrel backward the weapon is ready to fire, allowing from eight to ten shots per minute. After the barrel there are the trigger and the firing mechanism which is automatically cocked on reloading. The support of the grenade launcher embraces the handguard and for aiming with effectiveness there are special sights which are applied to the rifle; all of this contributes to give a rather different appearance to the M16 when fitted with the M203.

Almost every platoon in the US Army has at least one man (and often several) equipped with the M203 in his rifle. The grenades generally used are of high-explosive type (M406HE) but there exist as well smoke grenades, tracers, bengals, anti-riot grenades and other special types. The weight of the grenades is around 190-270 grams and their muzzle speed can reach 75 meters/second. The M203 is used against point targets at distances of 150-250 meters, but can be fired against area targets at his maximum range, which is 350-400 meters. At these distances, the prestations of the grenades, particularly the explosive ones, are limited by the amount of internal space required for the impact fuze, which has to be relatively large for being fully effective and safe, so the warhead has to be reduced and hence a larger number of grenades has to be fired against the target. Since this implies multiple grenades, diverse investigations in automatic grenade launchers have been effectuated already since the late 1960s, but none of these devices could be attached to a rifle. To improve things a bit, a new grenade of the M406 family has been developed, known as M384, which has a more powerful warhead and propellant charge.

M16 assault rifle

Categories: Small Arms - Infantry - Cold War - 20th Century - [General]


Website: Military History

Article submitted: 2016-10-15

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