The AK-47 is the 6th weapon in the game that comes with 100 ammo, 2 upgrades can be purchased: damage increasement and movement speed.
The AK-47 delivers low damage, has a high firing rate, and comes with 100 ammo. There is an upgraded version called the M16 which delivers medium damage, has a high firing rate, and comes with 250 ammo.
This weapon should only be bought for a mediocre Dual Uzis alternative. In this case Movement speed should be bought to move a bit faster. The M16 is an average weapon that would get the job done a bit faster, but it can only be bought with XCash.