A machine gun is a fully automatic mounted or portable firearm designed to fire rifle cartridges in rapid succession from an ammunition belt or magazine. Unlike semi-automatic firearms, which require one trigger pull per round fired, a machine gun is designed to fire for as long as the trigger is held down. Nowadays the term is restricted to relatively heavy weapons, able to provide continuous or frequent bursts of automatic fire for as long as ammunition lasts.
Machine guns are normally used against personnel, aircraft and light vehicles, or to provide suppressive fire, either directly or indirectly. They are commonly mounted on fast attack vehicles such as technicals to provide heavy mobile firepower, armored vehicles such as tanks for engaging targets too small to justify use of the primary weaponry or too fast to effectively engage with it, and on aircraft as defensive armament or for strafing ground targets, though on fighter aircraft true machine guns have mostly been supplanted by large-caliber rotary guns.
During the Cold War, short-range air defense (SHORAD) was dominated by gun-based vehicles. From the German Gepard to the American VADS to the Soviet Shilka, rapid fire autocannons were the preferred method of taking down helicopters and aircraft at close range. However, in modern times the guns have largely fallen out of favor. In the land forces modernization plan that planned to give the Marine Corps additional SHORAD, a missile only system was proposed. New Russian air defense vehicles are mounting only missiles as well, eliminating the gun component of the Pantsir system. The same situation is occurring with militaries around the globe.
This was due to two reasons, one was the many limitations of guns, they could only lock on from certain aspects, they took a long time to lock on, and they had limited range. There are videos of light AA guns being mounted on trucks and even some pickups by insurgents, and the accuracy of such systems is almost invariably very poor. The recoil of even a twenty-three millimeter system is enough to rock even a truck sideways. Outboard stabilizers are required for accurate fire if the chassis isn’t heavy and tracked like a Gepard or Tunguska. Second was the continuous improvement of missiles such as development of highly capable MANPADS such as the FIM-92 Stinger missile. These missiles can engage most targets in the gun firing profile quickly with more accuracy than guns themselves. With these missiles, greater capability can be put on lighter weight platforms, allowing a SHORAD network to be more spread out and mobile.
However, DARPA has launched a program to address the weakness of machine guns and make them effective in modern battlefield. In its FY21 budget request, the US Defence Advanced Research Projects Agency (DARPA) has asked for $13.27m to develop a missile with an attached gun. ‘Gunslinger’ aims to develop and demonstrate an air-launched tactical range missile that will feature a built-in gun system ‘capable of scalable effects and engagement of multiple targets’.
Cities have become the new battleground and Hybrid or Urban Warfare the greatest threat being waged by ISIS to Boko Haram to Hamas to Ukraine rebels. New air, ground and sea based platforms and munitions are desired having capabilities of accurately engaging targets in urban terrain with low collateral damage. the obvious advantage is that it would enhance the range of guns. The urban warfare also need PGMs that Can Attack Multiple Targets to increase the strike potential of a single aircraft or missile sortie. Submunitions and warheads that give PGMs the capability to attack multiple targets per weapon are desired. There is also threat of swarms of unmanned systems attacking whom with missiles adversaly affect cost benefit ratio. the machine guns with high rate of fire can attack multiple targets.
There is also need of smart submunitions individually capable of finding and homing in on targets. The section on Gunslinger does say that it would have the ability to “loiter” over a part of the battlefield, engaging multiple targets. This is something that is very likely to occur in dense urban areas, which the US military increasingly sees as a likely environment for future conflicts.
DARPA Gunslinger programme to combine gun with missile
The budget estimate document reads: “The Gunslinger programme will develop and demonstrate technologies to enable an air-launched tactical range missile system capable of multi-mission support. This system will utilise the high manoeuvrability of a missile system coupled with a gun system capable of scalable effects and engagement of multiple targets.” According to the document, the missile will address counter-insurgency (COIN) operations, close air support (CAS) and air-to-air engagement missions for use later by the US Air Force (USAF) and US Navy.
It explain the scope of the development effort saying: “The programme will address the system and technology issues required to enable development of a robust missile system considering (1) vehicle concepts possessing the required aerodynamic, propulsion, and payload capacity for a wide operational envelope, (2) the algorithms that support manoeuvring and target recognition to enable expedited command decision making for selecting and engaging targets and (3) approaches to incorporating modularity of design to reduce cost throughout the design and development process.”
For FY21 the programme aims to conduct trade studies including looking for information on propulsion systems, munitions, sensors, GPS and communications capabilities before developing ‘higher fidelity modelling and simulation environment to support program concept of operations’. DARPA is requesting $230m for the development of advanced aerospace systems, of which the Gunslinger programme is part, along with the Tactical Boost Glide programme, a joint DARPA-US Air Force project to develop hypersonic boost-glide systems.