"Kalashnikov's Gun"

MIT Technology Review published this article on the AK platform back in 2005. It notes:

The Kalashnikov is the most successful firearm in history. William Hartung and Rachel Stohr report in Foreign Policy that between 70 and 100 million of the weapons are in circulation, compared with just seven million U.S. M-16s. In Afghanistan, the AK-47 costs as little as $10.

... The AK-47 illustrates the power of incremental adaptation. As a tank sergeant in World War II, Mikhail Kalashnikov saw that most Soviet troops had only carbines [ed.: the author probably meant sub-machine guns] against the superior range of the German Sturmgewehr [ed. the STG-44, which used an "intermediate" rifle round]. While recovering from battlefield wounds, he began to create a design for a new weapon, one that could be assembled with relatively loose tolerances by relatively inexperienced workers, avoiding the supply bottlenecks that often resulted from the German cult of fine craftsmanship. A tractor plant originally produced the gun. Not only was the AK-47 simple to manufacture, but it could withstand rough handling in harsh terrain and climates.

The latter are good reasons why AK clones are good firearms for preppers.