Concurrently with the SCHV project, Springfield Armory was developing a 7.62mm rifle. 222 Remington cartridge case to meet the requirements. Springfield Armory's Earle Harvey lengthened the. Accuracy and ballistics equal to M2 ball ammunition (.Penetration of US steel helmet through one side at 500 yards.Select fire for both semi-automatic and fully automatic use.Bullet exceeding supersonic speed at 500 yards.Concerns about the recoil and overall effectiveness of 7.62 mm were overruled by the US, and the other NATO nations accepted that standardization was more important than the selection of a cartridge that was otherwise ideal. 280 round, including developing a version of the FN FAL in. The FN company had also been involved in the development of the. 280 (7 mm) cartridge when the selection of 7.62×51mm (.300) as the NATO standard was made. The British had extensive evidence through their own experimentation with intermediate cartridges since 1945, and were on the point of adopting the. At the time of selection there had been criticism that the recoil power of the 7.62×51mm NATO, when fired from a handheld lightweight modern service rifle, did not allow a sufficient automatic rate of fire for modern combat.

In 1954, the larger 7.62×51mm NATO rifle cartridge was selected as the first standard NATO rifle cartridge. The 7.62×51mm NATO and 5.56×45mm NATO cartridges compared to an AA battery 223 Remington cartridge designed by Remington Arms in the early 1960s. Though they are not entirely identical, the 5.56×45mm NATO cartridge family was derived from and is dimensionally similar to the. On 28 October 1980, under STANAG 4172, it was standardized as the second standard service rifle cartridge for NATO forces as well as many non-NATO countries. It consists of the SS109, L110, and SS111 cartridges. The 5.56×45mm NATO (official NATO nomenclature 5.56 NATO, but often pronounced 'five-five-six') is a rimless bottlenecked intermediate cartridge family developed in the late 1970s in Belgium by FN Herstal. Source(s): NATO EPVAT testing, QuickLOAD, SAAMI, C.I.P. NATO, Japan, South Korea, Taiwan, Australia, other major non-NATO allies

5.56×45mm NATO with measurement, left to right: Bullet, case, and complete cartridge

Calibre 5