if they were to ever duke it out with NATO, it comes in handy when they can use their opponents ammunition.
What NATO ammo can be used in Soviet/Russian weapons?
7.62 NATO isn´t compatible with any Russian weapon, since the heavy 7.62 (x54mm) is a rimmed cartridge, whereas 7.62x51mm NATO is a center fire cartridge.
Now you are wrong here aswel. Both 7.62x54mmR and 7.62x51mm NATO are centerfire cartridges. The case type for the russian one, is rimmed, and the NATO one is rimless. In the beginning of metalic cartridges, it was tought that a rimmed one would provide the best gas seal and extraction for both bolt action rifles as machine guns.
A rimless cartidge uses a groove to extract.
But neither are compatible. Nor are these bullets alike. The powder is diffrent, most 7.62x54mmR is berdan primed. The russian bullet diameter is actually 7.92mm while the 7.62x51mm NATO/.308 winchester is actually 7.82mm. you cant just pull the bullets and fire it in the other weapon.
7.62x39mm is also, not compatible.
Infact, never try to chamber a firearm for a diffrent cartidge, unless you are absolutely sure that nothing will go wrong.
The 7.5x55mm Swiss GP11 and 7.55x54.5mm MAS are almost identical in performance and size, but the chamber width is much diffrent and fire one in another...and disaster is close to happen
However with proper care, some things are compatible. .30-06 springfield and 7.62x51 NATO are not compatible. But both use eachothers bullets, powder and primers. So just get the proper cases and off you go!