and its bullet was relatively light. Testing of the 6.25×43mm was conducted from 1969 to 1971, when development ceased in favor of the smaller 4.85×49mm. In April 2022 in recognition of the decreased effectiveness of the NATO 5.56mm round particularly against personnel in body armour the American Army let a ten year contract to Sig Sauer for production of the XM5 rifle, XM250 Automatic rifle and 6.8mm (.277”) cartridge. Specifications Types of bullets and colours of tips: AP () API (): black Ball (): plain (unmarked), green, pink, yellow, brown Observation () ( WP): red Tracer (): white Note: Most cartridges have been observed with a purple annulus. Several experimental cartridge cases were made out of aluminium, in various colors including orange. Known manufacturers: Radway Green Fabrique Nationale Kynoch Performance The following comparisons are excerpts from a manual published by the "Small Arms Group Armament Design Establishment" from the Ministry of Supply: Variants .270 British: Designed at the same time as the .280 British . It has a slightly smaller bullet diameter of (versus for the .280) but a lighter bullet () with a greater muzzle velocity (), longer case () and shorter overall length (). Research was abandoned in 1948. 7 mm "Optimum": The original .280 British round with the bullet seated less deeply, giving an overall length of . 7 mm "High Velocity": Longer case (), with an overall length of . Similar bullet fired at . 7 mm "Compromise" (aka T65/7 mm): Necked down T65 (7.62×51mm NATO) to 7 mm. Case length , overall length , similar bullet fired at . 7 mm "Second Optimum" (7×49 mm): Designed by FN. Also known as the 7 mm "Medium" and the 7 mm "Liviano". FN would later sell FAL rifles chambered in this calibre along with a sizeable amount of ammunition to Venezuela. Longer case () with an overall length of . bullet fired at . 6.25 mm (6.25×43 mm): A British experimental cartridge designed during the early 1970s, using the .280/30 as a parent case, which was necked down to fit a smaller bullet. Comparable cartridges For .280 British: 7×44mm Danish, a Danish experimental cartridge fired by the Weibel M/1932 tested in 1936. 7mm BR Remington, a wildcat cartridge, at one time produced by Remington Arms) .308×1.5-inch Barnes and its necked-down 7 mm variant For 7 mm HV, 7 mm Compromise, 7 mm Second Optimum: 7mm-08 Remington See