An AK-47, as used throughout the planet, is a machine gun. A fully-automatic machine gun. You hold down the trigger, and the gun begins firing at a high rate until you remove your finger from the trigger, or run out of ammunition.
He did not build that.
He built a semi-automatic rifle that is functionally equivalent in pretty much every way to a hunting rifle you can buy at your local sporting goods chain store.
This harkens back to the "assault rifle" issue, which sees a type of rifle that is in every way equivalent to a semi-automatic hunting rifle labeled as an "assault rifle" because it looks more bad-ass than grandpa's deer rifle.
--edit--
I'm kind of ruefully laughing at myself here, as after three years of reading Hacker News, this is the topic that got me to angrily dive to my keyboard to make an account and comment. This from a total urbanite who gets nervous at being more than three blocks from a taxi stand and a wet bar, and who would probably need counseling if confronted by any woodland creature larger than a mid-sized rat.