The Mustang is the pinnacle of U.S. fighter aircraft. It is armed with six .50 cal machine guns, sacrificing firepower for speed. Enemy pilots find it difficult to meet in combat because of its high speed and maneuverability.
― Heroes & Generals
With a roll rate advantage, the P-51 can easily mimic enemies' movement before getting outturned. Such advantage stands out in group fights, where changing in direction of turn can allow you to avoid shots from lesser skilled pilots, while giving your wingman more time to shoot at the enemy chasing you. Unfortunately P-51 suffers from low damage output, combined with the wing mounted loadout of the guns means that it is slow to take down other planes
As a general rule of thumb having your wings perpendicular to the enemy chasing you is an easy way to avoid their gunfire