Trust is something you have to earn

Not contradicting what you said- as technically it is true, just expanding the info. 7.62x39 soviet 7.62 isn't the same as NATO 7.62 (roughly US .308.) it's an intermediate round, a little punchier than a .223 (5.56) but not as powerful as NATO 7.62. Its closer to a 30.30 In power, a little less than, making it barely suitable (but useable) for hunting game like deer. If it'll drop a deer it will drop a man pretty well. It's no small caliber round but isn't really a "battle riffle" round but more of an in between that has slightly better long range ballistics and stopping power than smaller rounds, but not the power and range of a larger round. It was designed and selected based off of early success in German light automatic riffles during WW2 based on engagement distances expected in 20th century urban combat.

You reference 7.62x51. Same dimensions but slightly less power than the .308 Winchester. The Nazis likes 7.92x57 Mauser which was remarkably similar to the American .30-06 and the Russian 7.62x54. I have an old Mauser that’s been converted to .30-06. They’re proper big game rifles. The .223 (or similar 5.56x45) is passable, but really more of a varmint round.

.223/5.56 arent very powerful. They're used in military applications where anti armor isn't a priority and standoff distances aren't expected to be in the football fields of length. They lack stopping power but are smaller and lighter with less recoil than battle riffle rounds. This allows more ammo per magazine and easier carry, a more compact weapon that doesn't need to be built to handle high power loads, simplification for automatic operation, and in theory greater control in rapid fire and less shooter fatigue. These rounds also tend to tumble- upon penetration they cause soft tissue damage to internal structures of the body. You can pick up dead after a battle, but injuries that take you out of a fight also tie up 2 to carry you out and medical care takes more resources than burial. Less dead- more wounded is part of the goal there. .308 and NATO 7.62 have slight shoulder differences and can't always be interchanged in weapons requiring one over the other.