I will take damage; Sheer Force only removes secondary effects like paralysation, burning, freezing (there are no sleeping and confusion moves for Sheer Force users yet), flinching and stat reduction.So Sheer Force Rufflet/Braviary won't take damage from Brave Bird?
Since Brave Bird don't offer any of these effects, it will not be powered up. It still is the stongest flying move, though.
Where can I find the formular for the accuracy of moves (affected by the ACC level)?