SR-47 (Stoner Rifle 47)
August 5, 2002; US Special Operations Command is now using small numbers of a new rifle, the SR-47 (Stoner Rifle 47). This is, basically, an American M4 carbine chambered to fire Russian 7.62x39mm ammunition and to use Russian AK-series magazines. The first six prototypes were rushed to units in Afghanistan last March, and more may have been sent since then (but any numbers are classified). The original idea was to provide special forces a rifle that had all of the "muscle memory" of the M4 carbine (location of the safety, etc.) but which used Russian ammunition. That way, an operator deep in enemy territory could use captured ammunition and would not leave tell-tale US-caliber casings behind. This was a relatively low-priority project until troops fighting their way into Afghan cave complexes found themselves unable to carry enough 5.56mm ammunition while literally awash in 7.62x39mm ammo stored throughout the caves. The original plan had called for the rifle to use American magazines but the special operators insisted that they would rather use "battlefield pick-up magazines". The SR-47 has other changes. US troops are used to hitting the magazine catch and letting gravity remove the empty magazine for them, something that won't work with Russian magazines. So, the SR-47 has an ejector spring to push the empty magazine out once the catch is released. The barrel is free-floating, making the SR-47 the most accurate AK-47 clone in the world. The prototypes shipped so far include sound suppressors, regarded as essential for cave fighting. Theoretical design work has begun on the SR-74 to use the Russian 5.45mm ammunition and magazines, should US forces go into a country that uses that caliber.
Photo from: A group effort from the users of this board.