two-man team who are grouped in a specialist Machine Gun Platoon the L7A2 in conjunction with a C2A2 Support Weapons Sight can provide battalion-level direct support fire at ranges up to and indirect map and range table predicted support/harassment fire out to . The indirect firing method exploits the 7.62×51mm NATO useful maximum range, that is defined by the maximum range of a small-arms projectile while still maintaining the minimum kinetic energy required to put unprotected personnel out of action, which is generally believed to be 15 kilogram-meters (147 J / 108 ft⋅lbf). With the tripod and FGM-148 Javelin sight unit indirect fire configuration, British troops in Afghanistan used the L7A2 at ranges of and over . The average elevation of Afghanistan and accompanying low ISA air density significantly contribute to extending the useful maximum range of small-arms projectiles. The L8A2 coaxial tank machine gun (replaced the L8A1) has a different gas valve switch (closed, single-position) when compared to the analogous Model 60-40, a different flash hider and a modified cocking handle. The weapon also has a trigger group that accepts electrical input and a lever in the feed tray that enables the belt to be removed without lifting the feed tray cover. Another tank machine gun is the L37A2 (succeeded the L37A1) designed to be mounted on tank turrets, in the commander's position, on wheeled armoured vehicles and on armored personnel carriers. It differs from the L8A2 primarily in its trigger, which was adapted from the L7A2 GPMG. The machine gun can be used in the ground role for self-defense, by dismounted vehicle crew members, the egress kit consists of an L7A2 barrel, bipod and buttstock. The L20A1 aircraft machine gun was based on the L8A2, from which it differs by having an electrical trigger and a slotted flash suppressor. The L20A1 can be converted to right-hand feed by changing several components in the feed mechanism. The L43A1, also developed from the L8A2, is a coaxially mounted tank machine gun used to sight-in the vehicle's main gun by firing ballistically-matched tracer ammunition at the target to confirm the trajectory visually. The weapon's barrel, fitted with a flash hider, has a reinforced and heavier structure that increases the weapon's accuracy especially during sustained fire.' China An unlicensed version is made for export by Norinco and made by Changfeng Machinery Co., Ltd as the CQ, 7.62 × 51 (Copy Version) (Now