M16 5.56mm Rifle

The M16 series of rifles was the standard issue shoulder weapon in the US military until 2005, at which point the M4 Carbine became the standard issue within the US Army. It marked a departure from normal ballistics in that it used a smaller, high-velocity round (5.56 mm caliber versus 7.62mm). This resulted in a smaller and lighter weapon, as well as smaller ammunition, significantly decreasing combat load.

The M16A1 was effective at ranges of less than 400-460 meters, the range within which United States experiences in World War II and Korea had indicated that small arms engagements would occur. The weapon permitted the heavily burdened soldier to maintain the same degree of firepower at a reduced weight. Finally, the M16A1 allowed every soldier to have an automatic fire capability whenever the situation required it, while the weapon's lighter ammunition facilitated battlefield resupply in greater quantities, enabling the resupply of field units for longer periods of time.

While the M16 series possessed less "stopping power" than the M14, it was found to be more accurate due to the reduction in recoil stemming from the smaller proiectile fired. During testing, both the M16Al and the AK-47 rifles were judged far more effective than the M14 in terms of expected casualties per combat load. In general, they produced 2 times the number of combat casualties that could be produced by the M14. Thus there was clear evidence of military utility in the M16A1 rifle, resulting in an increased degree of military advantage accruing to its user.

By 2000, the basic rifle squads consisted of a rifle squad leader and 8 soldiers, even if there were minor differences in operating procedure and specific equipment between infantry unit types. The rifle squad leader was the senior tactical leader of the squad and controled the squad's movement and fires. He conducted squad training and maintained the squad's ability to conduct tactical missions successfully. Each infantry squad was further organized into 2 4-man fire teams consisting of a team leader, a grenadier, and an automatic rifleman. The fourth member within each fire team was a rifleman. In mechanized infantry units, one of the 2 remaining riflemen was designated as an anti-tank specialist, and both were trained in the use of the Javelin anti-tank missile system and the M240B machine gun, either of which could be utilized if deemed necessary. One of these personnel was often further identified as the squad's designated marksman, a concept that began testing in the US Army as part of the Interim Brigade Combat Team development (which led to the modular force structure). The fire team leader was a fighting leader and led his team by example. The fire team leader controled the movement of his team and the placement of fires against enemy soldiers. He assisted the squad leader as required. The infantry squad fought by fire teams and buddy teams.

Firepower was the capacity of a unit to deliver effective fires on a target. Firepower would neutralize or suppresses the enemy in his positions, deceive the enemy, and support maneuver. Without effective supporting fires the infantry could not maneuver. Before attempting to maneuver, units had to establish a base of fire. A base of fire was placed on an enemy force or position to reduce or eliminate the enemy's ability to interfere with friendly maneuver elements. Leaders had to know how to control, mass, and combine fire with maneuver. They had to identify the most critical targets quickly, direct fires onto them, and ensure that the volume of fires was sufficient to keep the enemy from returning fire effectively, and the unit from expending ammunition needlessly.

The M16A1/M16A2 rifle was the most common weapon fired in built-up areas. The M16A1/M16A2 rifle and the M249 were used to neutralize enemy personnel, to suppress enemy fire and observation, and to penetrate light cover. Leaders could use 5.56mm tracer fire to designate targets for other weapons. Close combat was the predominant characteristic of urban engagements. Riflemen had to be able to hit small, fleeting targets from bunker apertures, windows, and loopholes. This required pinpoint accuracy with weapons fired in the semiautomatic mode. Neutralizing an enemy through an 8-inch loophole at a range of 50 meters was a challenge, but one that could be common in combat in built-up areas.

When fighting inside buildings, 3-round bursts or rapid semiautomatic fire was to be used. To suppress defenders while entering a room, a series of rapid 3-round bursts would be fired at all identified targets and likely enemy positions. This was more effective than long bursts or spraying the room with automatic fire. Soldiers would fire from an underarm or shoulder position, rather than from the hip. When targets revealed themselves in buildings, the most effective engagement was the quick-fire technique with the weapon up and both eyes open. Accurate quick fire not only neutralized enemy soldiers, but also gave the attacker fire superiority.

Within built-up areas, burning debris, reduced ambient light, strong shadow patterns of varying density, and smoke all limited the effect of night vision and sighting devices. The use of aiming stakes in the defense and of the pointing technique in the offense, both using 3-round bursts, were night firing skills required of all infantrymen. The individual laser aiming light could sometimes be used effectively with night vision goggles. Any soldier using night vision goggles was to be teamed with at least one soldier not wearing them.

The penetration that could be achieved with a 5.56mm round depended on the range to the target and the type of material being fired against. The M16A2 and M249 achieved greater penetration than the older M16A1, but only at longer ranges. At close range, both weapons performed the same. Single 5.56mm rounds were not effective against structural materials (as opposed to partitions) when fired at close range. The closer the range, the less penetration was achieved.

For the 5.56mm round, maximum penetration occured at 200 meters. At ranges less then 25 meters, penetration was greatly reduced. At 10 meters, penetration by the M16 round was poor due to the tremendous stress placed on this high-speed round, which caused it to yaw upon striking a target. Stress caused the projectile to break up, and the resulting fragments were often too small to penetrate.

Even with reduced penetration at short ranges, interior walls made of thin wood paneling, sheetrock, or plaster were no protection against 5.56mm rounds. Common office furniture, such as desks and chairs could stop these rounds, but a layer of books 18 to 24 inches thick could. Wooden frame buildings and single cinder block walls offered little protection from 5.56mm rounds. When clearing such structures, soldiers had to ensure that friendly casualties did not result from rounds passing through walls, floors, or ceilings.

Armor-piercing rounds were slightly more effective than ball ammunition in penetrating urban targets at all ranges. They were more likely to ricochet than ball ammunition, especially when the target presents a high degree of obliquity. Armor-piercing rounds were more likely to fly back at the firer. The 5.56mm round could be used to create either a loophole (about 7 inches in diameter) or a breach hole (large enough for a man to enter). When used against reinforced concrete, the M16 rifle and M249 could not cut the reinforcing bars.

The following common barriers in built-up areas could stop a 5.56mm round fired at less than 50 meters: One thickness of sandbags, a 2-inch concrete wall (unreinforced), a 55-gallon drum filled with water or sand, a small ammunition can filled with sand, a cinder block filled with sand (block would probably shatter), a plate glass windowpane at a 45-degree angle (glass fragments would be thrown behind the glass), a brick veneer, or a car body (rounds fired from M16A1/M16A2 rifles would likely penetrate, but not normally exit).

Although most structural materials would repel single 5.56mm rounds, continued and concentrated firing could breach some typical urban structures. The best method for breaching a masonarywall was by firing short bursts (3-5 rounds) in a U-shaped pattern. The distance from the gunner to the wall would be minimized for best results. Ranges as close as 25 meters were relatively safe from ricochet. Ballistic eye protection, protective vest, and helmet would be worn.