The most famous of all guns using the 7.62mm cartridge is the AK-47/AKM,and the FN FAL.
The round relies on primarily its weight,rather than velocity.
The 7.62mm round has alot of kick,and recoil is high,its weight overrides its velocity,meaning its more inaccurate then smaller caliber rounds,but this also means penetration is greatly increased.
The 7.62mm rounds weight will carry it through even the strongest of bullet resistant vests,and its size makes for devestating entry and exit wounds.
The NATO cartidge is more powerful and has greater range (hence it has often been used in machine guns such as the BREN and GPMG/FN-MAG, and in sniper rifles sucn as the SR-25), however the less powerful Soviet cartridge is more effective at wounding/killing a human at typical combat ranges (less than 400m).