No not the same, They have vastly different ballistics. 7.62x39 is an intermediate cartridge, whereas 7.62x51mm (.308) is a full power rifle cartridge with a much higher muzzle velocity and slightly heavier projectiles, and the 2 are not interchangable

No, not at all. The two cartridges have almost the same diameter bullet, but the case dimensions are very different. The .308 is also known as the 7.62X51, and also the 7.62 NATO, in addition to .308 Winchester. It is the chambering for the M-14 Battle rifle, the AR-10 predecessor to the AR-15,The 7.62X 39 Russian cartridge is the chambering for the well known AK-47 Russian battle rifle. The cartridge case is 12 mm shorter than the .308 case.

Max, no Sir. They are totally different non interchangeable cartridges. 7.62x39 top and 308/7.62x51 middle : quora.com/What-is-the-maximum-range-of-the-AK-47