An important component of the arsenal of any rifle unit is a light machine gun. With a relatively small size and weight, such a weapon is capable of providing a sufficiently high density of fire, which allows the machine gunner to act effectively together with other soldiers. In order to simplify production, light machine guns are sometimes designed on the basis of other weapons, primarily on the basis of machine guns. The Austrian light machine guns of the Steyr AUG family are a good example of this approach to small arms.
The first light machine gun of the family was the AUG HBAR (Heavy Barrel - "Heavy Barrel"), which is a basic automatic rifle with some changes due to other requirements. The main differences between the machine gun and the base rifle are a different barrel and a larger magazine. All other parts and assemblies of the weapon are unified. Moreover, by replacing the barrel, the Steyr AUG can become an AUG HBAR light machine gun and vice versa.
The main part of the AUG HBAR light machine gun is a distinctively shaped receiver made of aluminum alloy and placed inside a plastic case. To increase rigidity and strength, the receiver has several steel inserts. One of these parts is used to mount the barrel and lock the bolt. The thick-walled barrel of 5, 56 mm, 621 mm long, like other barrels of the AUG complex, is mounted in the receiver with eight stops that fit into the grooves of the receiver and is fixed by turning around its axis. The breech of the barrel is equipped with a gas block with a piston, as well as a front handle attachment. For ease of use, a muzzle brake and a folding two-legged bipod are installed on the barrel.
The automatics of the AUG HBAR light machine gun uses the energy of powder gases discharged from the barrel. A short-stroke gas piston drives the bolt group. Before firing, the barrel is locked on seven lugs by turning the bolt. In this case, the lugs are not located on the barrel, but on a special sleeve to which the barrel is attached. The bolt group moves along two hollow tubes. In addition to holding the bolt group, they perform additional functions: the left tube connects the bolt with the cocking handle, and the right one serves as the gas piston rod. For the extraction of spent cartridges, the bolt is equipped with an ejector and a spring-loaded reflector.
An interesting feature of the machine gun of other weapons of the Steyr AUG family is the ability to use two different bolts designed for right-handed and left-handed shooters. The bolt for firing from the right shoulder ejects the casings through the window on the right surface of the receiver. The second version of the shutter has a "reflected" design and ejects the sleeves to the left.
The trigger mechanism of the machine gun is made in the form of a separate unit located in the buttstock. USM is connected to the trigger with two rods. Several interesting technical solutions have been used in the design of the trigger mechanism of the Steyr AUG automatic rifle and weapons based on it. So, most of the trigger parts are made of plastic, and the number of metal parts is minimized. In addition, the mechanism does not provide for a separate fire translator. The functions of the translator are performed by the trigger: when not fully pressed, a single shot is fired, and for firing a burst, it is necessary to fully press it in. A button above the fire control handle that blocks the trigger is used as a safety catch.
The used automation allows you to shoot at a rate of up to 680 rounds per minute. The muzzle velocity of the bullet due to the use of a relatively long barrel reaches 950 m / s. The effective range of fire is not less than 350-400 m. Aiming is proposed to be carried out using an integrated sight. The optical sight with a magnification of 1.5x is built into the carrying handle and is similar to the sighting devices of other weapons of the AUG family.
The machine gun is powered from detachable box magazines for 42 rounds 5, 56x45 mm NATO. In addition, it is possible to use magazines for 30 rounds, originally intended for the AUG automatic rifle.
Due to the use of a long 621 mm barrel, the total length of the Steyr AUG HBAR light machine gun is 900 mm. Without cartridges, the weapon weighs 4, 9 kg. Thus, the light machine gun is only 100 mm longer and 1 kg heavier than the machine on the basis of which it was created. Such dimensions and weight, as well as a high degree of unification, contribute to the ease of use of the AUG HBAR machine gun in various units.
The Steyr AUG HBAR light machine gun coped well with the tasks assigned to it, but had some drawbacks. The main one is the tendency to overheating of the barrel during intensive shooting, with corresponding consequences for the accuracy and accuracy of fire. To solve this problem, the AUG LMG (Light Machine Gun) light machine gun was created. Once again, design changes were minimal, which made it possible to maintain a high level of unification of the two types of weapons. In fact, adjustments were made only to the firing mechanism and sights.
To reduce the thermal stress on the barrel in the AUG LMG project, a new trigger was used, designed for firing from an open bolt. This means that before firing, the shutter is delayed in the rearmost position and returns forward, sending the cartridge, only after pressing the trigger. Due to this, in the intervals between shots and during breaks in shooting, the chamber is open and the barrel can cool faster, more efficiently transferring heat to the surrounding air. In addition, firing from an open bolt allows you to increase the rate of fire. With a design similar to the AUG HBAR machine gun, the AUG LMG can fire up to 750 rounds per minute.
In the carrying handle of the AUG LMG machine gun there is a new 4x optical sight. The use of the new sight made it possible to simplify aiming at long ranges. At the same time, the firing range remained the same - over 350-400 m.
The AUG HBAR-T and AUG LMG-T light machine guns were the answer to the demands of the times. The only difference between this weapon and the HBAR and LMG is the new carrying handle. In order to increase the flexibility of use, the handle with the integrated telescopic sight has been replaced by a Picatinny rail assembly for mounting any compatible scope. The handle with a rail for mounting sights was borrowed from the modification of the basic AUG P Special Receiver assault rifle.
One of the main advantages of the weapon of the Steyr AUG family is its modular design. Depending on the current task, the shooter can use the most suitable barrel and bolt. In particular, the procedure for replacing individual units makes it possible to relatively quickly and easily make an HBAR or LMG light machine gun from the AUG automatic rifle. This feature of the AUG family of machine guns interested some customers. The military and security officials of several countries acquired a number of light machine guns of these models in the form of finished products and sets of replaceable modules for use with machine guns.
