One hundred and fifty years ago the new lever-action repeating rifles were too delicate to handle the stout cartridges used by the army's single shot rifles and were limited to use of smaller kind of cartridges used in revolvers. You could choose range or firepower; not both. Later, improvements in steels and design allowed repeaters to fire the full-power cartridges, and single-shot rifles ceased to be used for military purposes.
In the 1920s pistol-caliber sub-machine guns offered an analogous trade-off. You could have more firepower (rounds per minute) with a sub-machine gun, but only with a little short-range cartridges. (The recoil of a hand-held machine-gun firing a full-power rifle cartridge would be uncontrollable.) Again, you had the trade-off between power and range versus firepower.
With the shorter ranges of WWII's urban warfare, it was difficult to decide which was more useful -- a battle-rifle or a sub-machine gun. The sub-machine gun really wasn't powerful enough, but the battle-rifle was too slow and clumsy. Against Hitler's orders, a German research team produced a gun which split the difference. The power of each round fell in the middle between rifle-caliber and pistol/sub-machine gun caliber, and could be fired either one round at a time like a rifle, or in full-auto bursts. For urban warfare, this seemed to be the ideal compromise.
The AK-47 was a new design on the same principle, but sturdier, simpler to use, and cheaper to manufacture.
In the U.S. it has been forbidden since 1986 to introduce any additional full-auto weapons into the market for private citizens. Enthusiasts who think the AK-47 is cool are allowed to buy a version that lacks its full-auto capability. Without that capability it is not significantly different from an ordinary hunting rifle except for being significantly weaker in power, less sensitive to neglect and abuse, with less range and not quite as accurate. Even so, its availability does provide some benefits.
Stateside experience even with the crippled, non-automatic version of the AK-47 will prepare an American soldier overseas to pick one off a dead enemy and use it when his own rifle breaks -- training that the army itself has no facility to provide. And the gun's reduced power is nevertheless quite adequate for things like protecting a store from a mob of rioting looters and arsonists. Since storekeepers don't get to plan riots, the guns's reliability in the face of neglect makes it ideal for that mission.
I am not a religious person, I do not want to get into a debate on guns kill people v/s people kill people nor am I saying the inventor chose to pass away recently. But somehow having discussions on some war tool at this time of the year does not seem right. If others also feel the same, maybe we can refrain from posting in this topic for a few days?