air going over the nose of the sub sonic bullet is super sonic MAY be, not always. Remember, we're pushing air out of the way and venturi effect MAY increase the velocity. Just like lift of a wing, air has to speed up to get around the curved surface or low presure area is developed. Oh, that's a BT bullet! The velocity vector (forward and down, i.e. yaw angle) mean the velocity around the body is faster than at the nose (for ogival bullet). So pressure on the bottom of the body is greater than the top. Same for nose but as the body has greater surface area, force to generate yaw is greater. No matter what the forward velocity! Super sonic makes it worse due to pressure 'ridges' or 'shock waves'. THe pressure ridges 'move' relative tothe bullet as fps changes in the transonic region. Spin momentum keeps it stabilized to a point but sudden yaw will cause the gyro to presesand go off axis quite rapidly. The real and only sucessful solution is to keep it supersonic all the way. Really hard to do. That is why we have the 50BMG for 'reaching out and touching someone'! Only other solution is big, heavy and slow. We get to try stuff that is not optimal. Known as LOL.