Save the old position of the object at the end of every tick and set it's angle at the beginning of every tick to the angle from the old position to the current as calculated by the angle() expression.
EVERY TICK: set sprite angle to angle(oldx, oldy, sprite.x, sprite.y) set oldx to sprite.x set oldy to sprite.y
Alternatively have an invisible sprite "lead" as your projectile, attach the visible one to it via a physics joint, and set your angle to the invisible sprite.