They could shoot ours, but we could not shoot theirs!
In Vietnam, early on, we had m-14's, that fired 7.62 x 51 NATO ammo, before changing to the the M-16. Of course throughout the war we used the M-60 LMG, also in .30 cal NATO. I was told,as fact, that the Vietcong would scour the battlefields for the NATO ammo, and could fire it, single fire, from their Soviet Bloc bolt action rifles. As the NATO round did not have a rim, after firing it, to extract the shell casing, they used a cleaning rod, and would knock the spent casing from the chamber. I, for obvious reasons, have never attempted firing a NATO round from a Soviet 7.62 x 54R rifle.
Anyone out there ever tried this, or do I relegate this to the urban legends/bigfoot/UFO files??! Hmmm! Feedback would be appreciated, from a braveheart out there that has done this, and still has all the body parts, God issued them...DD