As _N4Z_ mentioned, most mid 60's through late 80's 7.62x54R surplus ammo were steel core, and will give you the performance that the 1/2" plate shows.
As many are finding out with the flood of Mosins, it is a potent round regardless of it's age, and was on par with the '06 and 8mm milsurp ammo back in the day.
NCsmitty