The .308 is still in my mind the only battle rifle round worth chambering now.
I love the AK74. The 5.45x39 caliber is like shooting a .22lr rifle. There is no recoil.
Certainly the 7.92X57, the 7.62x54R, the 7.62x63, and Brit .303 are all fine battle rifle calibers.
The only US president killed by shooting recently was killed by a 6.5 Mannlicher Carcano, so it can be done with less.