The cartridge can be found all across the world, from both militaries and hunters. The cartridge is widely used among militaries in the Asia, Africa, and even some European countries . It is also very popular amongst sportshooters. So after in zombie apocalypse it would be one of the easiest to find. But, users must pay attention if the ammunition is imported from army surlus. Some can be too rusted to be shoot, and can injure the shooter if fired.
Like mentioned before, it is used by both AK-47 and SKS. It is also used in some of the newer AK-103, and many producer are started to make new hunting rifles using the round. The cartridge is heavier than both NATO rounds.
The 7.62x39mm is a heavy hard kicking cartridge comparing to it's efficiency. AK-47 (the AKM and other lighter version will produce more recoil) produces more than 2 times the recoil of a M16 assault rifle. Having also huge bullet drop, the zeroing must be set for 150 yards on an AK-47 or a SKS. The ballistic coefficient is also very low.