This isn't unique to the USSR however. There are similar weapons in the US arsenal (M2 Browning for example) that are so well designed that is still in service

This isn't unique to the USSR however. There are similar weapons in the US arsenal (M2 Browning for example) that are so well designed that is still in service 84 years after initial introduction. Back when engineers had to use slide rules, and metallurgy wasn't as sophisticated, designers had to over-engineer machinery (and buildings, and bridges).