I will try to explain to you the sound of a 5.56 cartridge first off.
The M-16 and M-4 variants which both fire the 5.56 or .223 cal sound basically like a moderately loud .22cal Ruger long rifle..... If it had a plastic stock and was missing most of it's mounting screws. Basically from the shooter position you hear more of the plastic rattling and the buffer spring than you will of the actual report of the weapons cartridge.
An AK sounds like well...... Loud, very "thuddy" (if that's a word), and has a distinct feel to the sound usual to most wood stocked rifles. If you want a good idea of what one sounds like go pick up an SKS its a different round but very similar. Or if you cant seem to find an SKS, try firing a .30 Cal rifle with a wood stock then imagine the sound without a cracking noise.
Trust me the wood matters, it has something to do with dampening the vibrations when firing. An easy test for this would be to get two .22cal Long rifles one with a wooden stock and one having a fiberglass FRP or plastic stock, both rifles must be the same model, and two identical .22cal cartridges. You will notice an incredibly different sound from both rifles.