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Advanced Combat Rifle [ACR]

The Army's Advanced Combat Rifle Program, managed by the Close Combat Armaments Center, Picatinny Arsenal, New Jersey, underscored the enduring importance of the rifle to close combat. Between August 1989 and April 1990, the US Army held a technology demonstrater Advanced Combat Rifle (ACR) competition. The entries could not reach the 100 percent improvement over the M16A2, which had only just entered service, sought by the US Army.

In August 1989 the Army and the Air Force began testing the first of four prototypes of rifles to assess whether improvements in rifle design and technology warranted replacing the M16A2 rifle. The Army wanted a rifle that would significantly improve the average soldier's ability to hit the target under battlefield conditions, or at least to double the number of hits per trigger pull. With the M16A2 the probability of a battlefield hit is 20 percent at 100 meters, 10 percent at 300 meters, and 5 percent at 600 meters.

The weapon user community had long expressed a need for a new or enhanced rifle for the combat soldier. The Advanced Combat Rifle (ACR) program was developed to accommodate this need. The purpose of the ACR program was to develop and assess rifle concepts that will increase hit probability beyond that of the M16A2. The increase in hit probability rests on two assumptions. First, during the stress of combat, aiming errors will be large and second, firing multiple projectiles per trigger pull, either serially or simultaneously, will compensate for this large aiming error by increasing the probability of hit beyond firing a single projectile.

The degree of improvement depends on the aiming error associated with the trigger pull, the number of rounds fired, and the size of their dispersion. The projected improvements of ACR concepts in comparison to the M16A2 further assume that the aiming error, although large, will be the same for semiautomatic and burst fire. The larger the aiming error, the greater the improvement. This is true because as aiming error increases, the opportunity for the additional projectiles to contribute to hit probability increases. Conversely, for small aiming errors, improvements in hit probability for burst systems are diminished.

Analyses of battlefield marksmanship suggested that several task-induced stressors would generate the large aiming errors expect in combat. The most apparent are the expectation of short target exposures, unknown target locations, multiple targets, and random combinations of these.

By 1990, the analytical community accepted an aiming error function derived from the performance of the worst third of many field experiments, offered by AMSAA, as that which may be experienced during combat stress. Theoretically based analyses led to a consensus in the small arms community that approximately an 8-roilmean extreme spread for a three-round burst is optimal for a serially fired system.

Two American and two European manufacturers submitted prototypes that represented the latest in rifle design, technology, and ammunition. Three of the rifles used 5.56-mm. ammunition, the size currently used by the Army, and the other used 4.92-mm. ammunition. In addition to conventional ammunition, most of the weapons could fire highly lethal ammunition that included rounds containing flechettes and double bullets. The tests, which were being held at Fort Benning, Georgia, were completed in mid-FY 1990.

This program investigated technologies to improve the soldier's combat performance. Most targets are covered or obscured, and move unpredictably, and a consequence are exposed to hostile fire for limited periods of time. When coupled with the level of marksmanship training provided the average soldier and the stress of combat, a soldier's aiming errors are large and hit probability is correspondingly low. While the current M16A2 rifle is capable of acceptable accurady out to six hundred meters, the probability of an average soldier hitting an enemy at three hundred meters is ten per cent. The goal of the ACR program is to demonstrate the potential of a one hundred per cent increase in hit probability. The ACR Program is an effort to identify technologies worth inclusion in an Advanced Combat Weapons program.

Of the four weapons systems under evaluation in the ACR Program, two fired conventional jacketed bullets, while two fire one-piece steel flechettes or dart-like projectiles.

Heckler and Koch was a caseless system that fired a 4.92mm guilding metal clad steel jacketed lead core 6111let weighing 49.2 grains at a muzzle velocity of 3,000 feet per second. The weapon operated in three modes: single shot, three-round salvo bursts (at a rate of 2,000 rounds Per minute), or automatic fire at a rate of 450 rounds per minute.

Colt was a derivative of the current M16A2 rifle, duplex ammunition which consists of a brass-cased cartridge containing two bullets. Each is a 5.56mm con.ventiopl guilding metal jacketed steel core bullet. The front bullet weighs 35 grains; the rear bullet, 33 grains, each fired at 2,900 feet per second. The front bullet travels to the aim point while fhe rear bullet is offset to a controlled dispersion to increase hit probability. The weapon operates in single shot and automatic fire modes, the latter at a rate of 850 rounds per minute.

AAI was a brass-cased system that fires a one-piece steel flechette projectile 1.51mm indiameter, 42mm long weighing 10.2 grains, at a velocity of 4,600 feet per seeond. The weapon operates in single shot and three-round salvo burst modes, the latter at a rate of 1,700 rounds per minute.

Steyr-Mannlicher is a plastic-cased system that fires a one-piece steel flechette projectile 1.5mm in diameter, 42mm in length, weighing 10.2 grains, at a velocity of 4,900 feet per second. The weapon operates in single shot and three-round burst modes, the latter at a rate of 1,200 rounds per minute.

In contrast, the M16A2 M855 bullet isa 5.56x45mm guilding metal jacket, lead core with steel penetrator in foiward portion of bullet projectile weighing 62 grains fired at a muzzle velocity of 3,050 feet per second; the NATO M80x51mm bullet is a 7.62 guilding metal or guilding-metal clad steel jacket, lead core bullet weigh50 grains fired at a muzzle velocity of 2,868 feet per second; the Soviet AK-47 utilizes a 7.62x39mm guilding-metal clad steel jacket, lead core, bullet weighing 120 grains fued at a muzzle velocity of 2,350 feet per second, while the Soviet AK-74 is a 5.45x39mm guildmg-metal clad steel jacket, steel core with lead in forward portion of bullet projectile, weighing 53 grains and fired at a muzzle velocity of 2,920 feet per second.

A myriad of factors enter into the effect a bullet has upon striking its target, to include bullet weight, bullet mass, range, velocity on impact, portion of the body struck (e.g., arm, leg, torso, head), portions affected by the permanent wound cavity (e.g., soft tissue or bone, vital organs, etc.), entry angle into the body, distance traveled point-forward before yawing, degree of bullet yaw on impact, deformation or deflection of the bullet caused by the soldier's equipment prior to the bullet's entry into the body, degree of bullet penetration, tissue disruption, the physical condition of the soldier, number of wounds inflicted, and delay prior to treatment of the wound.

A complete comparison between the projectiles under consideration and current assault rifle ammunition can best be accomplished through examination of wound profiles produced through firing the projectiles in question into ordnance gellatin.

Two of the weapon systems under consideration (AAI and Steyr-Mannlicher) employ a flechette projectile. The issue of the legality of flechettes was thoroughly discussed in the course of the multinational conference that produced the UNCCW. The conferees found no basis to suggest that flechettes violated the prohibition on unnecessary suffering contained in article 23e of Hague Convention IV of 1907. No provision was adopted to prohibit or limit the use of flechettes.

In their early years of development and employment, a number of myths emerged regarding flechettes and their incapacitation effect or lethality; for example, it was alleged by some that flechettes were designed to bend on impact with soft tissue solely for the purpose of increasing the suffering imposed on an enemy combatant, and that the wounding effects of flechettes were substantially greater than comparable munitions, whether artillery fragments or assault rifle bullets. Research associated with the UNCCW negotiations did much to clear the air with regard to flechettes. Not all flechettes bend on impact, for example. Even if a flechette is designed to or has a tendency to bend or otherwise deform on impact, this would not necessarily constitute a violation of the prohibition on unnecessary suffering; it would be legally permissible if military necessity requires such a characteristic in order to increase the projectile's incapacitation effect or lethality at its maximum effective range, and is not incorporated into the design merely for the purpose of needlessly aggravating the wounding effect of the projectile.

Flechettes employed in the weapons under consideration apparently do not exceed the lethality or incapacitation effect of contemporary assault rifle projectiles even when those flechettes bend, and in many cases (depending in large measure on range) have lethality or incapacitation effects that are less than contemporary assault rifle projectiles at the same ranges. Subject to information that might be discerned in the course of the wound ballistic testing being conducted by BRL, neither flechette round under consideration can be regarded as contravening the law of war prohibition on unnecessary suffering.

All of the ACR weapons fire multiple projectiles per trigger pull. The Colt weapon employs the multiple launch technique of firing two bullets per Fdrtridge. The AAI, H&K and Steyr systems utilize the serial launch technique. Each of these weapons fires three rounds in a high rate of fire burst to fire three projectiles per trigger pull. The purpose of each is to increase the probability of hitting the enemy soldier against whom'fire is being directed. 'here will be occasions in which an enemy combatant will suffer multiple wounds. At issue is whether the employment of weapons that could produce multiple wounds is prohibited by the unnecessary suffering prohibition contained in article 23e of the Annex to the 1907 Hague Convention IV.

The issue was considered in the course of the UNCCW conference. An argument was made by a one delegation (Sweden) that if a soldier can be disabled by a single projectile, then multiple-projectile weapons that might cause a soldier to suffer more than one wound would lead to unnecessary suffering. This argument was specifically directed at certain types of fragmenting munitions, such as the cluster munition and the Claymore mine, but is equally applicable with regqd to all of the weapons systems under consideration.'The ikue became moot when it was pointed out to the delegation from Sweden that its armed krvices were equipped with the very types of weapons it was condemning.

It was the conclusion of the conferees that the purpose for development of such munitions was to increase the probability of hitting soldiers within range of the weapon rather than increasing the suffering of an individual soldier. The conferee recpgnized that some'soldiers likely will suffer multiple wounds owing to the volume of firepower extant on the-modern battlefield. The proposal to place restrictions on fragmenting weapons was not accepted by the participants in the UNCCW conference. Similarly, it is concluded that the fact that some soldiers may suffer multiple woundsin the employment of any of the candidate weapons systems does not violate the prohibition on unnecessary suffering contained in article 23e of the Annex to the 1907 Hague Convention IV.

The technologies employed in the weapon systems under consideration are militarily necessary in order to increase the probability of hitting an enemy soldier and achieving a necessaryrlevel of incapacitation under a variety of conditions at a variety of ranges out to 600 meters.

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Page last modified: 07-07-2011 02:41:47 ZULU