GTA Vice City Stories (1984): The Vice City Stories rendition is accurate, both by size and look. It's a proper AK-47, however the sound is the same as the one used for the Ruger in GTA Vice City.
GTA San Andreas (1992): The GTA San Andreas version of the weapon is a Norinco Type 56. It is often used in Gang Warfare. The model is very low detail and, strangely enough, is significantly larger than it should be, being two-thirds as long as Carl Johnson is tall.
GTA Liberty City Stories (1998): This rendition is exactly the same as the Vice City Stories rendition with no actual differences.
GTA III (2001): The GTA III version of the weapon is mostly accurate, but appears smaller than it should be. It is an AK-47, not an AKM, as evidenced by the muzzle break and the stock. The handle should also be the same color as the stock, instead of black.
GTA IV (2008): The version ingame is the AK-47. Its size is accurate, as is the magazine size and overall performance. The AK-47 is quite accurate, but its range and power are slightly less then the NOOSE Assault Rifle.
Locations
GTA III
Saint Mark's, Portland Island - In a secluded area behind Cipriani's Ristorante. From Cipriani's Ristorante, use the sidewalk on the south side of the block and head east. Proceed up the hill until you reach a driveway that cuts across the block. Go onto the driveway then turn west. Go to either the north or south of this building and continue west along the ledge. Go around the corner and proceed to the middle of the block. You should see a ramp leading down into the secluded area. The weapon icon is in the corner near the ramp and next to a body armor icon.
Trenton, Portland Island - On top of Liberty Pharmaceuticals (behind the large sign) near an adrenaline icon, a health icon, and a body armor icon. Jump from the elevated tracks near the northeast side of the large complex to access.
Fort Staunton, Staunton Island - Tucked beside a construction trailer underneath some ruins north of the sharp angled turn in the northeast part of the construction zone.
Red Light District, Portland Island - On a roof to the left of Paulie's Revue Bar. Run to the back of the club, go up the stairs and start walking towards the water tower and jump on that roof when you're close enough.
Downtown - On the roof of the VCPD police station. The roof is accessible by using a helicopter or using the set of stairs on the alleyway where an Enforcer and PCJ-600 are parked.
Ocean Beach - On the roof accessible by a set of stairs at the long alleyway going behind Ocean Drive. The roof is north of the Patrol Invest Group's headquarter and a rampage is also available on that very roof.
GTA IV
The AK-47 is referenced in-game as the Assault Rifle. It can be purchased from the back-alley gun shops for $3,500 and each additional magazine costs $80. It can also be purchased from Little Jacob for $2,450 with each additional magazine costing $55.
Industrial - Can be found on a catwalk of a defunct manufacturing structure behind the abandoned warehouse the player rescues Roman during the mission Hostile Negotiation.
Charge Island - Can be found within one of the far rooms of the old hospital on the south side of the island. The hospital is the same from the mission The Snow Storm.