designed to optimally support both cartridges. Ammunition capacity for weight comparison The first confrontations between the AK-47 and the M14 rifle came in the early part of the Vietnam War. Battlefield reports indicated that the M14 was uncontrollable in full-auto and that soldiers could not carry enough ammo to maintain fire superiority over the AK-47. A replacement was needed, as a result, the Army was forced to reconsider a 1957 request by General Willard G. Wyman, commander of the U.S. Continental Army Command (CONARC) to develop a .223 caliber (5.56 mm) select-fire rifle weighing 6 lbs (2.7 kg) when loaded with a 20-round magazine. This request ultimately resulted in the development of a scaled-down version of the Armalite AR-10, called ArmaLite AR-15 rifle. During testing it was found that a 5- to 7-man team armed with the ArmaLite AR-15s has the same firepower as 11-man team armed with M14s. Also, soldiers armed with ArmaLite AR-15s could carry nearly three times more ammunition as those armed with M14s (649 rounds vs 220 rounds). The ArmaLite AR-15, officially designated Rifle, caliber 5.56 mm, M16, was later adopted by U.S. infantry forces as the standard issue rifle. Here is a table comparing rifles based on a maximum ammunition load in box magazines of . 5.56mm NATO versus 7.62mm NATO Hit probability refers to the ability of a soldier to concentrate on firing in spite of their weapon's recoil and noise, which is noticeably different between the two cartridges. The 7.62 NATO has twice the impact energy of the 5.56 NATO, preferable if a target is protected by higher level armor, especially at "medium" range. If not, both rounds normally penetrate satisfactorily through enemies up to 600 meters, approximately. A 5.56 NATO round fired from a barrel has a flatter trajectory than a 7.62 NATO round fired from a barrel of equal length, while the 5.56 NATO fired from a barrel has the same trajectory as the 7.62 NATO from a 20 in barrel, as well as the same time of flight. A 7.62 NATO round reaches 50 percent of its velocity within of the barrel when fired, so decreasing the barrel length for close quarters combat results in increased muzzle pressure and greater noise and muzzle flash. Military cartridges Australia Cartridge, Ball, F1 (1985-2010?): 5.56×45mm FN SS109 equivalent produced by Thales Australia, formerly Australian Defence Industries (ADI). Cartridge, Ball, F1A1 [Green tip] (2010–present):