maybe alot of people have already know about this...
1) ak47 is the easiest gun to make headshot everytime.
2) just target your cross hair at the enemy head and hit 2 time. enemy will die if u hit it correctly at his head.
3) if the enemy does not have helmet he will die with 1 hit on his head.
4) if it's very hard for u to target the enemy head. if he is running around
5) hit 4 bullet at his body. he will die eventually. 2 time and another 2 time.
6) dont hit 30 bullet straight with ak47 or u will not hit the enemy at all.
7) ak47 is a very hard riffle to control

but it can be like a sniper without a zoom.