I'm not sure if this is intentional or not, but while the AK74 spawns at the police station and cars, the mags spawn at neither, only at the long barracks. I'm fairly sure this is a mistake, because what's the point of finding an AK74 at the police station in Elektro, but knowing the nearest place you will find a mag is Kamenka, completely across the map.
No one I know has found a mag at any of these locations (and I have found over 15 AK74s), and the online map DayzDB which takes info directly from the game files confirms this.
If a dev could possibly look into fixing this for the next update that would be great. Thanks :)