Sometimes you hear things and you gotta ask where somewhat intelligent people get their information. I have heard many times over the years Former Soviet Union (FSU) guns can shoot our ammo but we cannot shoot theirs. This was put out in several schools and familiarization ranges that I attended prior to 1989. In this post I would like to discuss this and the possibilities. A little bit of science about a chamber and kindergarten physics. When a bullet fits into a chamber its snug. Then the bolt locks onto the chamber making an extremely tight custom fit around the cartridge. The primer goes off then ignites the gunpowder which then explodes sending forces outward forward and rear. The chamber counters the outward forces and the locked bolt counters the rearward forces making the front where the bullet is the path of least resistance.
The first round I will cover is the Soviet 7.62x 54R This round was used in the Mosin Nagant who's inception was 1891. At that time the US was using the Bolt Action 6MM (6x60mm) Navy Winchester 1895 (Navy Lee), Also the Krag Jorgensen 8mm and 30 caliber lever action rifles. By their Designations they came after the Mosin Nagant. The only US round for that time that I can think of off hand that might be able to be used in Nagant is the 30/30. The 30/30 Winchester is in fact 7.62mm x 51 and it is a rimmed cartridge.
However In 1903 the US fielded the M-1903 Springfield chambered in 30/03 (7.62x65mm) and in 1906 the 30/06 (7.62x63mm) Both these rounds cannot be used in the Mosin Nagant because they are too long. The bolt will not close or lock hence the trigger cannot release the firing pin.
Ok so lets look at the 30/30 and the 7.62x54R. as I already stated the 30/30 is 3mm shorter than the 54R and it is a rimmed round. The length isn't too bad I saw a .308 cartridge that was shot through a 30/06 and all that happened was that neck stretched out to the same size as the rest of the case. So I guess if you were being attacked by a horde and all you had was .308 and a 30/06 bolt action rifle it would suffice. However I cannot attest to accuracy.
Lets look at the rim. the 54R has a 14.40mm rim and the base diameter is 12.37 where as the 30/30 has a 12.9 mm rim and a 10.7mm base. From this information the 30/30 would fit loosely into the chamber the bolt can't hold onto it. If engaged by the firing pin it would slide forward or at the extreme (I never say never) if somehow the primer was engaged the round would more than likely become a ruptured cartridge.
Lets get to the AK-47 which shoots a 7.62x 39 cartridge Its inception at the time was 1949. The US was carrying the M-1 Garrand (30/06 7.62x63 which won't fit) and the closest to this round the M-1 Carbine which shot the .30 Carbine (7.62x 32.76mm) Again the length is shorter, the cartridge is nowhere near the shape of a 7.62x39 (Forces and Physics) and its base diameter is smaller than the 7.62 x 39. Again if by chance you do get it to fire you are going to have a ruptured round and good luck getting it out of the chamber unless to have a ruptured cartridge tool. Later on in life the US adopted the M-14 with it's 7.62x51 cartridge which again is too long and would not permit the bolt to lock
Quickly the AK-74 which is 5.45x39 using a 5.56x45mm look at the numbers! It don't FIT!
Last I got from a friend of mine that was an F-4 WSO The US used the M-61 Vulcan which shot a 20mmx 102mm round. The Soviet MIG-21 used the GSh-23 which shot a 23x115mm round. if by chance you did get the thing to fire with American ammo. Do you want to be clearing a ruptured cartridge in a dogfight.
A possibility is that maybe the soviets employ an insert to fire our ammo like the chamber insert for an M-1 Garand to be converted from 30/06 to .308. Though I have found no evidence of this. Now what I have heard of is battlefield procurement on both sides. IE use their weapon and ammo. Reload our 7.62 brass with their bullets and powder (US only because soviet and European ammo is berdan primed this is 'Merica after all we use Boxer priming pockets). Never have I heard about FSU nations using our ammo out of their guns.
One note I mentioned locking at the beginning of this article. It is one of the 8 steps of function in a firearm. Except in weapons with a blowback operating system utilizing a heavy bolt (IE M-3 Grease gun and PPSh41) These weapons do not utilize a locking system. Aim well and shoot straight
