Seems like your setup for the question was created in such a way to require the AK47 as the "right" answer.
In what battle would you never have the downtime to clean?
Without the stupid setup, I'd choose AR-15 every day!!
.45acp, .40 S&W, 9mm, .38 Spl, .380 acp, 22lr
12 gauge, .223/5.56x45mm, 30-30 Winchester
2 Chron. 7:14 Christians must seek His face