Back in 80s a guy I knew got a killer deal on a case of “AK” ammo. He couldn’t get it to work in his AK and brought gun and ammo for me to check out. This ammo wasn’t 7.62 x 39mm. This was steel cased and when I measured it to research what it was it turned out to be a 7.62 x 45mm that Yugoslavia chambered for their rifle in early 50s. Just to stay separate from Soviet Bloc. Still have 50rds of that ammo.