. 276 Pedersen The . 276 Pedersen ( 7 x 51 mm ) round was an experimental 7 mm cartridge developed for the U . S . Army and used in the Pedersen rifle and early versions of what would become the M1 Garand rifle . Summary . Developed in 1923 in the United States , it was intended to replace the . 30 - 06 Springfield in new semi - automatic rifle s and machine guns . When first recommended for adoption , M1 Garand rifle s were chambered for the . 276 Pedersen , which held ten rounds in its unique en - bloc clip s . The . 276 Pedersen was a shorter , lighter and lower pressure round than the . 30 - 06 , which made the design of an autoloading rifle easier than the long , powerful . 30 - 06 . The U . S . Army Chief of Staff Gen . Douglas MacArthur rejected the . 276 Pedersen Garand in 1932 after verifying that a . 30 - 06 version was feasible . History and technical notes . Pedersen ' s round fired a 0 . 284 - inch ( 7mm ) bullet . Comparable to the contemporary Italian 6 . 5x52mm ( 0 . 268 in ) Carcano or the Japanese 6 . 5mm ( 0 . 264 in ) Arisaka , it produced velocities of around 2 , 400 feet per second ( 730 m / s ) with 140 or 150 grain ( 9 . 1 or 9 . 7 g ) projectiles . The case was two inches ( 51 mm ) long with significant taper . Tapered cases require the use of highly curved magazines similar to the Kalashnikov , although for the short magazines of the Pedersen and Garand rifles , this was immaterial . Both waxed and bare cartridges were made for the Pedersen and Garand rifle respectively . At the time of its introduction , the . 276 Pedersen was a solution to a significant problem . The U . S . Army wanted a general issue autoloading rifle that would fire the . 30 - 06 cartridge , but such a rifle was prohibitively large with existing designs such as the Browning Automatic Rifle and French Chauchat . A weapon of the same weight as the M1903 needed to fire a smaller cartridge . Pedersen ' s cartridge was viewed as a compromise as it was underpowered compared to most military rifle cartridges . This decreased recoil energy made possible a reliable , lightweight semi - automatic rifle with existing technology . Despite these early problems with semi - automatic designs , Garand ' s design was eventually able to handle the . 30 - 06 cartridge ; the need for a lighter caliber dissolved . The Pedersen rifle was unsuitable for the . 30 - 06 and it , too , was dropped . Immediately after World War II , British designers introduced a series of intermediate - power 7mm cartridges for a different reason than Pedersen . They sought an answer to the Germans ' highly successful 7 . 92mm " Kurz " and various studies on the matter . The U . S . stuck with . 30 caliber mostly out of a desire to have a common cartridge between rifle and machine gun combined with the perceived necessity for effectiveness out to 2000 yards . Development of a shorter . 30 round specifically for use in an autoloading rifle began after the war , and resulted in the 7 . 62×51mm NATO , a shorter and slightly lighter round that gave nearly identical ballistics to the . 30 - 06 . Interestingly , the British studies on various cartridges culminated in the . 280 British cartridge , which shared ballistic similarities to the . 276 Pedersen in caliber , bullet weight and velocity . Despite the failure to adopt either the . 276 Pedersen or later . 280 British , the concept of an intermediate power military cartridge of a 6 . 5 to 7mm diameter was far from dead . Shortly after the 7 . 62mm NATO cartridge was adopted , Armalite submitted their AR - 15 for evaluation , the U . S . Army suggested they redesign the gun to fire a . 256 caliber projectile . Although this suggestion was fruitless , the Army later engaged in many studies of a 6mm SAW cartridge . They , once again , sought to replace autoloading rifle and machine gun cartridges with one round . Current studies are focused on the 6 . 8mm Remington SPC and 6 . 5mm Grendel commercial cartridges although their purpose is to improve on the 5 . 56×45mm cartridge , not to develop a replacement for the 7 . 62×51mm NATO as well .