The competition, which lasted almost three years, was attended by Sig Sauer, Lone Star Future Weapons, which collaborated with General Dynamics-OTS, and Textron Systems. The army competition commission decided that the M4 and M16 carbines, as well as the 5.56 mm M249 light machine gun, would be replaced by Sig Sauer 6.8 mm weapons.
So far, the rifle is called XM5, and the machine gun is XM250. After the weapon has passed military tests and the necessary improvements have been made, the “X” designation will be abandoned. The first trial batch of rifles and machine guns, along with $20.4 million worth of high-tech fire control optics, will be used to continue field testing.
The contract for 120,000 weapons - 107,000 rifles and 13,000 machine guns - was signed for ten years. In 2017, Sig Sauer also won a contract to supply M17 and M18 pistols to the Army, which are now replacing the Beretta M9, which has served for three decades. Thus, the company becomes the main supplier of most small arms for close combat forces. The contract value is $4.7 billion. Another 2.7 billion will be spent on the M115 high-tech computerized fire control system.
The new rifle and machine gun are based on the recently commercialized civilian version of the adaptable MCX-SPEAR multi-caliber rifle.
The XM5 has a folding stock with six fixation positions, a two-stage trigger. The gas piston, which ensures the return of the bolt to the combat position, can be adjusted. There are two firing modes - single and automatic. The handle on the fore-end can be easily moved, adjusted to the anatomy and habit of the shooter. The rifle is equipped with a full-length Picatinny rail. The store holds 20 rounds. Various polymeric materials are widely used in the design of the rifle.
A feature of the XM5 and XM250 is that the weapon is equipped with a quick-release, turn-latch silencer and flame suppressor SIG SAUER SLX. It differs from conventional suppressors by an internal multi-flow channel instead of traditional baffles. The SLX series suppressors are designed for use with supersonic munitions.
The suppressor was required in order to reduce the negative effect of a powerful ammunition. A bright muzzle flash and shock wave would greatly affect both the shooter himself and his comrades, especially when shooting in confined spaces.
Bullet weight reaches 9 grams. The initial speed is 915 meters per second. As a result, a very high pressure arises in a relatively short barrel about 33 centimeters long, which increases the load on the locking unit and leads to increased heating of the barrel.
In addition, the new cartridge creates a strong recoil momentum. It is even larger than that of the regular NATO cartridge of 7.62 mm. Therefore, the new XM5 and XM250 use different schemes to reduce perceived recoil.
New ranged weapons are designed for melee forces. These include infantrymen, scouts, fire spotters, as well as engineers and medics of forward units. If the Special Operations Forces Command and the Marine Corps also choose Sig Sauer, then the current contract provides for an increase in deliveries to 250,000 units. All other US military personnel will continue to use M4 rifles and M249 light machine guns.
In part, the decision to change small arms close combat was due to the emergence of modern personal protective equipment for military personnel in Russia and China. Cartridges of caliber 5.56 have lost their effectiveness. It became clear that it was necessary to increase the kinetic force of the bullet, the range and accuracy of aimed fire.
Initially, the US Army considered 6 millimeters, but then came to the conclusion that it was not too different from 5.56. Then they leaned towards 6.8 millimeters. Experienced firing has shown that a bullet of this caliber retains its lethality at a distance of 600 meters, twice as long as the caliber that goes down in history.
The new ammunition makes the rifle almost a kilogram heavier than the M4, but the machine gun will be, as Pentagon officials assured journalists, four kilograms lighter than the M249. “Both weapons provide a significant improvement in accuracy and range capabilities. They are lighter, shoot deadlier ammunition, soften recoil, provide improved barrel performance, and include built-in muzzle and flash suppression,” the Army press release says.
The Army is currently funding the construction of a new production line at its munitions plant near Independence, Missouri. Construction is scheduled to be completed by fiscal year 2025. Until that time, Sig Sauer will produce ammunition in its own factory, which produces similar cartridges for the hunting version of the rifle.
The M157 fire control system is supplied by Vortex Optics. In this device, not only a conventional sight is connected, which is stored in case of electronic failure, but also optics with variable magnification up to eight times, sighting lasers in the visible and infrared ranges, a laser rangefinder, a ballistic calculator connected to a set of atmospheric sensors, a digital display, wireless communication between platoon fighters and compass.