Weapon Name- M7 Caseless
Round Type- 5.56mm (5.72mm x 35mm caseless)
Over-all length- 30 inches, 26 inches, 23.5 inches
Barrel length- 24 inches, 20 inches, 17.5 inches
Weight- 6.5 lb, 6 lb
Rate of Fire- 600 RPM
Feed Mechanism- Detachable Box Magazine
Round Capacity- 20, 40, 100
Effective Range- 300 meters
Range- 700 meters
Accuracy- 1 MOA, 1.25 MOA
Accessories- Picatinny Rails
Quick switch firing mechanism- N/A
Scope/Sights- Picatinny Rails, 4x Thermal Scope
Muzzle Velocity- 940 m/s, 850 m/s
Firing System- XM8 Short Stroke Gas Piston
Miscellaneous/electronic information-
Basic Information
The weapon is essentially an enlarged bullpup XM8 firing the 5.56mm NATO cartridge. Based on the firing system, it combines aspects of the LSAT with the XM8, to allow the weapon to possess the capability to fire caseless ammunition, primarily the seal on the bolt which seals the round in the chamber. The XM8 uses an extremely reliable short stroke gas piston, which is substantially more reliable than direct impingement systems, while still possessing the same level of accuracy and low recoil. Compared to long stroke gas pistons, the weapon has a lighter bolt and piston mass and a shorter action, which reduces the recoil significantly, while still retaining much of the high reliability and durability. Key differences with the original XM8 are ambidextrous controls, a quick adjustable right or left ejection port, being bullpup, and a higher degree of modularity. While the original XM8 was designed to work with form fitting pieces to increase their cohesion with accessories and the weapon, to provide greater ergonomics and reduced weight, it lacked standard modularity available from equipment such as picatinny rails. This firearm possesses the option for the same close fitting accessories, however it also possesses optional picatinny rail attachments, with keyhole mounting, that allows the picatinny rails to mounted to the firearm. This opens up the weapon to being able to use a variety of different weapon attachments, such as lasers or scopes. It possess a lower profile top rail, instead of the raised rail found in the traditional XM8, as well as a non-reciprocating, fixed non-folding charging handle. The slimmer profile as well as changed accessories makes the weapon lighter, or approximately 1 pound lighter than a standard XM8. The shorter cartridge which is only about an 1 inch long, shortens the length of the firearm by about 2 inches.
The weapon is essentially patterned off of the XM8, however it is much smaller. The short stroke gas piston is considered to be more reliable than direct impingement systems while retaining the same low recoil and high accuracy, and in general is more smoothly operating than long strike gas pistons (less recoil, muzzle rise, and higher accuracy). The firing system is based off of the XM8 which uses a short stroke gas piston system, similar to that in the AR-18, FN SCAR, or XM8 In July 2007, the US Army announced a limited competition between the M4 carbine, FN SCAR, HK416, XCR, and the previously-shelved HK XM8. Ten examples of each of the four competitors were involved. Each weapon fired 60,000 rounds in an "extreme dust environment." The purpose of the shoot-off was for assessing future needs, not to select a replacement for the M4. The XM8 scored the best, with only 127 stoppages in 60,000 total rounds, the FN SCAR Light had 226 stoppages, while the HK416 had 233 stoppages. The M4 carbine scored "significantly worse" than the rest of the field with 882 stoppages. However, with the HK416, 117 of the 233 malfunctions were from just one of the 10 weapons. Over-all this gives the weapon between 4-8 times higher reliability than the M4 carbine or similar firearms, with a variety of operating conditions being less hazardous to the over-all functioning of the firearm, including sandy or wet condition. The weapon also has substantially higher heat tolerance than most firearms, even higher than most similiar firearms. While an M16 is only expected to be able to realistically fire 15-20 rounds a minute, the XM8 can fire over 80 rounds per minute with relatively little difficulty, which is roughly equal to the firing rate of the M249 machine gun, and twice that of the M27 IAR at 36. Heckler and Koch engineers fired 4 high-capacity magazines, with 100 rounds apiece, in less than 5 minutes from their XM8 entrant, or 400 rounds in less than 5 minutes.
The weapon uses a detachable polygonal cobalt chrome "flow formed" 6 groove 1:7 inch (1 complete turn in 1 in 7 / 180mm) right hand turn barrel; the barrel is made of an alloy that contains more than 50 percent cobalt. The barrel is roughly 13% heavier than standard steel barrels, but is more erosion and corrosion-resistant and is designed to retain high strength during long-term exposure to high temperatures. Cobalt alloys are frequently used in the aerospace industry, such as the hot-gas section of turbine engines. A proof of concept M240 7.62mm x 51mm NATO barrel, in practice, had 24,000 rounds test-fired through it, causing it to reach temperatures of 1,100 degrees, without failure. A steel barrel would have failed under such treatment. The barrel itself, combined with polygonal rifling, is extremely durable, and has a minimum 20,000 round barrel life, although it is possible to extend this or get use out of the rifle after the minimum is reached. The barrels come in 10, 14.5, and 20 inches.
The 5.56mm, while less powerful than many alternatives, is significantly lighter weight, and possess far less recoil. Lighter and weaker than the 6.5mm Grendel and .264 Winchester, it serves the role primarily with an armor piercing submachine gun. The firearm is designed to utilize a 5.56mm cartridge with a 6.2 gram bullet possessing 2075 joules, generating a velocity of 815 m/s from a 20 inch barrel. While called the 5.72mm x 35mm, the cartridge shares the same diameter as the 5.56mm, being .224 inches in diameter. Like how the .38 and .357 magnum share the same caliber size but use a different number to denote it, the 5.72mm is essentially the same diameter as the .223, or 5.56mm x 45mm NATO cartridge. However, the bullet utilized is usually larger, at 6.2 grams (95 grains), although it is compatible with the 4.1 gram variant. This bullet has a lower velocity for the same level of energy but has a higher BC of .6, vs. .2 with the 4.1 gram bullet. The variant used in the caseless firearm uses more powerful, faster burning propellant, giving it roughly equivalent ballistics to the .224 Valkyrie. This round has a far longer effective range than the standard 5.56mm x 45mm NATO using the Sierra Match king 95 grain bullet, and slightly greater energy. At 600 yards the round still has approximately as much energy as a .357 magnum (1000 joules), and has the same energy as a handgun round at 1100 yards (500 joules), remaining super sonic until 1400 yards. This is in comparison to the original 5.56mm, the round possess 1000 joules at 175 yards, 500 joules by 375 yards, and loses super sonic velocity by 550 yards.
The weapon utilizes a 100 round spring assisted rotary magazine, which spins the rotary mechanism with each backwards cycle of the bolt. This is designed to provide additional energy in to pushing forward the follower, clicking the magazine forward, which in turn helps to spin the magazine. Instead of being entirely dependent on the spring of the magazine, which is consequently heavier and less reliable as it enlarges like most drum magazines, instead the magazine has an additional device which helps to push the floor plate forwards. The magazine is designed much more like snail drum magazine in construction, and forms a circle around a single axis, however this is shaped in order to fit inside the bullpup weapon. This is much more reliable given the assisted feeding the rearwards action of the bolt provides to help load each round in to the firearm. This is similar in effect to a belt fed weapon, however it functions almost identically to a linkless belt system.
Each barrel possess a muzzle break designed after the surefire muzzlebreak. Though there are numerous ways to measure the energy of a recoil impulse, in general a 10% to 50% reduction can be measured. Besides reducing felt recoil, one of the primary advantages of a muzzle brake is the reduction of muzzle rise. This lets a shooter realign a weapon's sights more quickly. This is relevant for fully automatic weapons. The weapon also possess a hydraulic recoil buffer similiar to that in the M249. The Hydrualic recoil buffer extends all the way back in to the stock, The design of the weapon and it's straight back recoil impulse, as well as the tighter, more steady grip on the weapon, combined with the impact gel recoil pad, makes the weapon very easy to use and relatively comfortable. The weapon uses a Blackbox round counter that can be hooked up to an LCD screen to show the rounds remaining. The magazines are generally color coded, which provides indication of how many rounds are within each magazine, although loading in another magazine that does not meet the criteria can result inaccurate round counting predictions; the round counter mechanism itself, however, will not falter. The weapon is made from composites and polymers similar to the P90 and XM8, to both reduce the cost and weight as of the weapon, as well increase the durability. The weapon fires from a closed bolt for both maximum accuracy and reliability. The weapon has picatinny rails, and thus an array of different sights are available for the weapon.
