Steyr ACR (Advanced Combat Rifle)

History of the Steyr ACR (Advanced Combat Rifle)

In the late 1980s, the U.S. Army undertook a program to identify potential successors to the long-serving Colt M16 series automatic riflesthe standard rifles of the U.S. Army and many allied nations. This program is recognized as the Advanced Combat Rifle (ACR) program, and its main goal is to significantly increase the probability of "first hit". At this point in history, the M16 had been in front-line service for almost 30 years, including rather problematic performance during the Vietnam War (1955-1975), and was later improved by the M16A2 variant.

The plan spans three main phases (referred to as Phase 1, Phase 2 and Phase 3 for short) and includes submissions from major gun manufacturers such as AAI Corporation, Heckler & Koch, Steyr and Colt in Austria. Steyr submitted the "Steyr ACR", a weapon designed around firing a 5.56x45mm SCF (Synthetic Case Flechette) inside a smoothbore.

For their ACR, Steyr opted for a bullpup configuration similar to their popular Steyr AUG series assault rifles. The bullpup arrangement only identifies the ACR as a weapon, with its action and magazine advance behind the trigger group.

Such an arrangement then allowed the use of a full-length barrel, but in a more compact body of assault weapons - the action embedded in the enlarged butt, stowed in the shoulder when firing. Like the AUG, the ACR has a mostly plastic body with metal interiors to minimize manufacturing costs and overall weight bearing. The frame contains a two-piece plastic cover, one over the main part of the frame and the other to accommodate the stock. The grip and trigger group are concentrated on the bottom of the frame. The front end is fully wrapped and doubles as a fore grip and heat shield.

The muzzle is M16-style slotted and protrudes only slightly from the plastic body. A straight, proprietary clear plastic magazine is inserted into the bottom of the stock, and the magazine release button is just behind the feed slot. Sling loops are located at the top of the shoulder rest and on the left side of the front flap for shoulder straps. Across the top of the rifle is a rib assembly with two gaps that serves primarily as a basic sighting device, but can also be used as an ad hoc carrying handle. Optics can be attached to this assembly as needed.

As with the M16, a pull-on spring-loaded charging handle is mounted to the rear of the sight assembly, and simply pulls back to raise the weapon. Spent cartridges are ejected through an opening under the stock between the magazine well and the pistol grip.

Overall, the ACR proved to be a clean and somewhat futuristic assault weapon design worthy of 21st century warfare. Like the M16, the Steyr ACR uses a pneumatic system in which a sleeve wrapped around the barrel assembly is propelled back during the action and connected to a vertical sliding chamber that manages the function of the cartridge.

The ACR measures a barrel length of 30.7 inches and a curb weight of 7 lbs (the former is achieved with a no-powder configuration, the latter is achieved with heavy use of plastic). The barrel was not rifled, but remained smoothbore, with a length of 21 inches.

The detachable magazine holds 24 ready-to-fire rounds in a typical stacked arrangement. The basic firing action of the ACR allows three rounds of semi-automatic fire.

One of the more unique aspects of the ACR's design is its ammunition - essentially a clear plastic casing containing a steel fin-stabilized arrow (dart) in a cartridge-like casing. The plastic case holds the rockets, casings and propellant, which eventually ejects down the gun as usual during firing. Each feather is 1.6 inches long.

Once the propellant is driven by the firing pin, the cartridge case and arrow travel down the barrel in the usual way. As soon as he left the barrel at the muzzle, the cartridge case fell. The arrow then continues to head in the desired direction (of course, falling casings tend to be dangerous to nearby friendly forces, especially at the exit velocities involved).

Although it is very different from traditional spherical tip-based powder cartridges, this cased missile method actually performed quite well in U.S. Army tests because its high-velocity exit allowed small changes in overall trajectory and therefore accuracy higher.

The overall muzzle velocity of the muzzle is a staggering 4,700 to 4,900 feet per second compared to the M16's 3,100 feet per second.

Ultimately, none of the submitted assault rifle designs met the requirements of US Army authorities enough to warrant official acceptance. Compared to the standardized M16A2 model widely used at the time, the increase in first-hit capability proved to be insignificant, problematic or overly complex.

It is conceivable, however, that the data gathered through the ACR's assessment could one day influence a yet-to-be-coming Steyr Flechette-oriented assault weapon design.

Specification

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