Steyr ACR

Between 1989 and 1990, the US Army made a concentrated effort to replace the M16A2 assault rifle. To this end, they launched the Advanced Combat Rifle program, the first phase of which started in February 1986. While the Advanced Combat Rifle program itself was shelved without attaining the hoped-for results, it did catalyze some significant advances in assault rifle technology and design. One of the most prominent products top come out of this era was the gas operated, flechette-firing assault rifle known as the Steyr ACR. This weapon, which was designed by Steyr Mannlicher, has certain limited points of aesthetic similarity with the Steyr AUG, a 5.56 mm NATO bullpup assault rifle. However, this weapon is far too unique to be compared in any way at all with any preexisting firearms.

The most physical feature of the Steyr ACR is probably the almost completely covered barrel. The body consists of a sleek and very user-friendly polymer case, an AUG-styled pistol grip, and a carrying handle that extends almost all the way to the muzzle and acting as an additional sighting device. This handle can also accommodate a telescope for more refined fieldwork such as sniping. There are three firing modes available - safe, semiautomatic and fully automatic. It fires 5.56 x 45 mm SCF or synthetic case flechettes, which are cylindrical plastic units composed of gunpowder, three shoe-like sabots and a primer ring. The rising chamber firing mechanism, which is based on advanced kinetic energy projectile technology, is unique and has nothing to do with the conventional ammunition round firing mechanism. The flechettes are extremely stable projectiles with notable penetration at almost any range.

The Steyr ACR shoots these devices, which are stored in a 24-round box magazine, singly or in bursts of three. The fact that they are extremely lightweight makes such a high-capacity magazine possible. The most advantageous feature of these projectiles is the fact that they travel along a completely flat trajectory at speeds that allow for efficient penetration of body armor. The flechette concept had first been tackled in the 60s, without any success, and the Steyr ACP marked a revival of the best kind. With this assault rifle, the concept was given its first realistic incarnation.

The rifle itself weighs approximately 3.23 kilograms in an unloaded condition and has a muzzle velocity of 1480 meters per second. However, it has been found that the muzzle velocity tends to vary because of varying pressure levels caused by inherent weaknesses in the plastic case. This was viewed as a significant drawback during tests carried out in the United States in conjunction with the Advanced Combat Rifle program. The breech is actuated by the aforementioned gas system. The Steyr ACR is approximately 25% shorter than the M16A2, with a barrel length of 540 mm, and has been specifically designed for maximum maneuverability in situations that do not offer much elbow space to the shooter. Because of this, the Steyr ACR is eminently suited for the requirements of airborne and special forces. The entire unit is extremely modular in design and construction, having less than 1000 moving parts - a fact that makes for very realistic maintenance in combat conditions.

While the Steyr ACP is doubtlessly an outstanding example of modern armament technology, it failed to meet the stringent requirements of the Advanced Combat Rifle program. These, it should be remembered, required the entrant to be a 100% upgrade on the M16A2 that it was meant to replace. Since the program itself died a natural death, and also since no other entrant was chosen for the same reasons of noncompliance to the stated parameters, the Steyr ACP was not judged on this basis. It remains an excellent field weapon with remarkably advanced features and Steyr-Mannlicher has understandably gone ahead with improving on the original design, evidently continuing to hope that this assault rifle will, sooner or later, find favor with the US Army.

The Steyr-Mannlicher entrant for the U.S. Advanced Combat Rifle competition was considered to be an excellent example of modern technology, but, like the other entries it could not reach the 100 percent improvement over the M16A2 demanded by the U.S. Army. The company have said that it represents their view of the next generation of assault rifles and they will continue to develop it privately and will probably offer it for consideration some time early in the next century.
The rifle uses a gas system to actuate the breech mechanism, which is quite unusual and which is built around the special cartridge. This cartridge is of plastic, a plain cylinder with the priming composition arranged in a ring around the inside of the case, just ahead of the base. A fin-stabilized flechette lies inside the case, its fins positioned by the primer ring and the body held by a polycarbonate sabot, and surrounded by propellant.

The breech consists of a block which carries the chamber. At the commencement of firing an operating arm is held back against a spring. On pulling the trigger this arm is released to run forward, take a cartridge from the magazine and load it into the chamber. The chamber then rises vertically to a position behind the barrel, where it is locked by a spring catch. Above the chamber is a fixed firing pin, pointing downwards, and as the chamber rises so this firing pin passes through a hole in the chamber block and, just as the chamber aligns with the barrel and locks, strikes the ring primer and fires the cartridge. The flechette is driven up the barrel; gas, tapped from the barrel into a surrounding chamber, drives a piston which is actually a sleeve around the barrel. This drives the operating arm back, unlocking the chamber and lowering it to the loading position. As the trigger is pressed for the next shot, the arm goes forward again, and the cartridge entering the chamber pushes out the spent plastic case of the previous round, ejecting it forward of the weapon. There is no rim on the plastic case, so no obstacle to this forward ejection.

The rifle is a bullpup design, with the magazine almost at the rear of the stock. The mechanism is enclosed in a plastic outer casing, there being something of a family resemblance between this and their well-known AUG rifle. A carrying handle above the weapon is extended almost to the muzzle, so acting as a sighting rib for snap shooting, and iron sights are fitted; a telescope can be quickly attached to the carrying handle. The barrel is rifled with a twist of one turn in 85 inches, giving roll stabilization to the flechette to improve accuracy.

The only real defect of the design, as revealed in the U.S. tests, is that the flechette tends to leave the cartridge at varying chamber pressures due to inconsistent strength in the plastic cartridge case. Varying pressures mean varying muzzle velocities and changes in trajectory from shot to shot, so that accuracy suffers. This, however, is simply a question of testing various materials and assembly methods until a consistent release pressure can be obtained, and it is probable that Steyr has already solved this, ready to offer the rifle to the next applicant.

The Steyr-Mannlicher entrant for the U.S. Advanced Combat Rifle competition was considered to be an excellent example of modern technology, but, like the other entries it could not reach the 100 percent improvement over the M16A2 demanded by the U.S. Army. The company have said that it represents their view of the next generation of assault rifles and they will continue to develop it privately and will probably offer it for consideration some time early in the next century.
The rifle uses a gas system to actuate the breech mechanism, which is quite unusual and which is built around the special cartridge. This cartridge is of plastic, a plain cylinder with the priming composition arranged in a ring around the inside of the case, just ahead of the base. A fin-stabilized flechette lies inside the case, its fins positioned by the primer ring and the body held by a polycarbonate sabot, and surrounded by propellant.

The breech consists of a block which carries the chamber. At the commencement of firing an operating arm is held back against a spring. On pulling the trigger this arm is released to run forward, take a cartridge from the magazine and load it into the chamber. The chamber then rises vertically to a position behind the barrel, where it is locked by a spring catch. Above the chamber is a fixed firing pin, pointing downwards, and as the chamber rises so this firing pin passes through a hole in the chamber block and, just as the chamber aligns with the barrel and locks, strikes the ring primer and fires the cartridge. The flechette is driven up the barrel; gas, tapped from the barrel into a surrounding chamber, drives a piston which is actually a sleeve around the barrel. This drives the operating arm back, unlocking the chamber and lowering it to the loading position. As the trigger is pressed for the next shot, the arm goes forward again, and the cartridge entering the chamber pushes out the spent plastic case of the previous round, ejecting it forward of the weapon. There is no rim on the plastic case, so no obstacle to this forward ejection.

The rifle is a bullpup design, with the magazine almost at the rear of the stock. The mechanism is enclosed in a plastic outer casing, there being something of a family resemblance between this and their well-known AUG rifle. A carrying handle above the weapon is extended almost to the muzzle, so acting as a sighting rib for snap shooting, and iron sights are fitted; a telescope can be quickly attached to the carrying handle. The barrel is rifled with a twist of one turn in 85 inches, giving roll stabilization to the flechette to improve accuracy.

The only real defect of the design, as revealed in the U.S. tests, is that the flechette tends to leave the cartridge at varying chamber pressures due to inconsistent strength in the plastic cartridge case. Varying pressures mean varying muzzle velocities and changes in trajectory from shot to shot, so that accuracy suffers. This, however, is simply a question of testing various materials and assembly methods until a consistent release pressure can be obtained, and it is probable that Steyr has already solved this, ready to offer the rifle to the next applicant.

The Steyr-Mannlicher entrant for the U.S. Advanced Combat Rifle competition was considered to be an excellent example of modern technology, but, like the other entries it could not reach the 100 percent improvement over the M16A2 demanded by the U.S. Army. The company have said that it represents their view of the next generation of assault rifles and they will continue to develop it privately and will probably offer it for consideration some time early in the next century.
The rifle uses a gas system to actuate the breech mechanism, which is quite unusual and which is built around the special cartridge. This cartridge is of plastic, a plain cylinder with the priming composition arranged in a ring around the inside of the case, just ahead of the base. A fin-stabilized flechette lies inside the case, its fins positioned by the primer ring and the body held by a polycarbonate sabot, and surrounded by propellant.

The breech consists of a block which carries the chamber. At the commencement of firing an operating arm is held back against a spring. On pulling the trigger this arm is released to run forward, take a cartridge from the magazine and load it into the chamber. The chamber then rises vertically to a position behind the barrel, where it is locked by a spring catch. Above the chamber is a fixed firing pin, pointing downwards, and as the chamber rises so this firing pin passes through a hole in the chamber block and, just as the chamber aligns with the barrel and locks, strikes the ring primer and fires the cartridge. The flechette is driven up the barrel; gas, tapped from the barrel into a surrounding chamber, drives a piston which is actually a sleeve around the barrel. This drives the operating arm back, unlocking the chamber and lowering it to the loading position. As the trigger is pressed for the next shot, the arm goes forward again, and the cartridge entering the chamber pushes out the spent plastic case of the previous round, ejecting it forward of the weapon. There is no rim on the plastic case, so no obstacle to this forward ejection.

The rifle is a bullpup design, with the magazine almost at the rear of the stock. The mechanism is enclosed in a plastic outer casing, there being something of a family resemblance between this and their well-known AUG rifle. A carrying handle above the weapon is extended almost to the muzzle, so acting as a sighting rib for snap shooting, and iron sights are fitted; a telescope can be quickly attached to the carrying handle. The barrel is rifled with a twist of one turn in 85 inches, giving roll stabilization to the flechette to improve accuracy.

The only real defect of the design, as revealed in the U.S. tests, is that the flechette tends to leave the cartridge at varying chamber pressures due to inconsistent strength in the plastic cartridge case. Varying pressures mean varying muzzle velocities and changes in trajectory from shot to shot, so that accuracy suffers. This, however, is simply a question of testing various materials and assembly methods until a consistent release pressure can be obtained, and it is probable that Steyr has already solved this, ready to offer the rifle to the next applicant.