From WikiGTA - The Complete Grand Theft Auto Walkthrough
|Grand Theft Auto III
GTA San Andreas
Liberty City Stories
Grand Theft Auto IV
The AK-47, (short for the Russian term for Automatic Kalashnikov rifle of 1947) or assault rifle in GTA IV, is a powerful assault rifle with a bigger range than a machine gun. The magazine can hold 30 rounds. You can buy an AK-47 at the local Ammu-Nation. The AK-47 is not present in GTA Vice City, here you'll find the Kruger.
In GTA San Andreas, you reach the 'gangster level' at 30% weapon skill, and 'hitman level' at 100%.