It's a lot of give and take. During the Vietnam war and any since when the 7.62x39 has gone against the 5.56, when the terrain goes from open plains to having to fire through trees and undergrowth (or building walls), it's nice to have a slower heavier round that can plow through things.I think there isn't anything wrong with either 5.56x45 or 7.62x39 or 5.45x39 for defensive round. I doubt the 7.62 is as good ballistically, but . . . there is a lot of cheap ammo out there.
It's a lot of give and take. During the Vietnam war and any since when the 7.62x39 has gone against the 5.56, when the terrain goes from open plains to having to fire through trees and undergrowth (or building walls), it's nice to have a slower heavier round that can plow through things.
No coincidence at all. It was thought then that the next World War would take place in eastern Europe, an environment where the 5.56 or 5.45 would prosper. The 7.62x39 is a lot like a .30-30, it's slow and heavy, and best suited for things within 200 meters. It may work well in the Urals but not so well in a farming plain where your targets are out around 500 meters or more.You don't suppose it's a coincidence that the USSR had advisers in Vietnam and suddenly decided to develop a 5.45mm round that's a ballistic twin to 5.56mm right around the end of that war, do you?