How does AK47 work?

Answer 1

"To fire, the operator inserts a loaded magazine, moves the selector lever off of safety, pulls back and releases the charging handle, aims, and then pulls the trigger. In this setting, the firearm fires only once (semi-automatic), requiring the trigger to be released and depressed again for the next shot. With the selector in the middle position (full-automatic), the rifle continues to fire, automatically cycling fresh rounds into the chamber, until the magazine is exhausted or pressure is released from the trigger. As each bullet travels through the barrel, a portion of the gases expanding behind it is diverted into the gas tube above the barrel, where it impacts the gas piston. The piston, in turn, is driven backward, pushing the bolt carrier, which causes the bolt to move backwards, ejecting the spent round, and chambering a new round when the recoil spring pushes it back."

Cited from: Department of the Army. Operators Manual for AK-47 Assault Rifle. 203d Military Intelligence Battalion