The AK uses a .310 bullet and not a .308 round.
Of course I'm probably erring on .310, it might be .311 or .312. I know it's not 308 though.
I wonder how often our guys run into the 5.45 rather than the 7.62. That's suppose to be one nasty bastard =:-O
Standard groove diameter of foreign military rifles in 7.62 x 39mm is .311", and most factory ammunition is loaded with bullets near that diameter. The Ruger Mini-30, the first U.S. commercial rifle to be produced in this caliber, has a groove diameter of .308". The design of it's chamber throat enables it to handle bullets of .308" and .311" diameters.
The "standard" AK round is the 7.62x39 russian, which translates to a diameter of 30 cal.
The .308 is also considered a 30 cal round, but the .308 cartridge packs about 66% more punch.
The AK series has several different loads.
The Ak-47 is 7.62 while the Ak-74 is 5.45
You can usually tell the difference between them from a distance because the 47 usually has a wooden stock and is milled out of a solid piece of metal and the 74 has a synthetic stock and created out of stamped metal.
7.62X39 bullet is nominally .311 diameter.