>>3 http://mentalfloss.com/article/27455/what-made-ak-47-so-popular
"The AK-47’s major selling points are its simplicity and its ability to take a beating. The rifle was designed to be easy to use, easy to repair, and reliable. The ruggedness of the gun makes it the perfect weapon for dirty, sandy conditions or for soldiers who might not be super disciplined about maintaining their firearms. Its simple firing mechanism means that the gun jams very rarely. Depending on conditions of use, an AK-47 can have a service life of anywhere from 20 to 40 years."