Every innert projectile launched from a barrel drops at the rate of 16 feet per second per second of flight. All projectiles drop at the same rate - however, the higher the ballistic coefficient (coefficient of friction) and the higher that projectile's velocity, the further it will travel in each second of flight.
For example, a round ball might travel only 200 yards in the same time a slower starting but better shaped projectile travels 400 yards. The better shaped projectile loses velocity at a slower rate and therefore travels further in the same period of time. The drop will be the same at their respective ranges - 200 yards for the round ball, 400 yards for the better, more streamlined projectile.
Neither shoots flat, as all projectiles (as Keb noted) start dropping as soon as they leave the muzzle.
Higher sights and longer zero ranges give the illusion of flatter shooting, but also increase the mid range height of the ball.
We round ball shooters have an advantage over slug shooters inside normal hunting ranges, in that we can drive a much lighter round ball at a velocity that overcomes the faster slowing down the ball possesses. The slug shooter is confined to lower than round ball speeds due to pressures generated, and therefore has to contend with greater drop over normal ranges than we do. This then shows the round ball can be driven flatter shooting than the other projectile - but - it isn't flat shooting by definition. Even my high velocity .17 cal. modern rifles that seem to shoot like laser beams, really aren't flat shooting over any range.
We might call it "flat shooting" in a relative context, though, in comparrison to another ball or bullet.
