M1A2 and A2 SEP have an air engagement mode in the Firecontrol system used mostly with the MPAT round which is the replacement for the Heat round. It is used mostly for low level subsonic AC (Helicopters) The MPAT round has a switchable fuse setting for ground or air (proximity) twist and switch.
The .50 cal rounds that would penetrate tanks top or underbelly would be API (Armor piercing Incendiary Rounds) which were used in abundance but would be hard pressed to penetrate anything over 2 inches of RHA which the Germans used in abundance.
I used .50 cal API rounds with great effect in Iraq on Toyota engine blocks and the like. They are way harder than ball ammo for sure so the distortion to the round on the bounce I think would be minimal at the angle they would have to hit to richocette upward under a tanks so I guess it would be possible to kill or at least disable a tank like that.
As a gunner in an abrams crew you are taught how to engage aircraft with sabot which depending on the aircraft and angle of it's attack it is theoreticaly possible to hit it but would really be a waste of ammo in 99% of cases..
16 years as a tanker in case anyone questions the knowledge
M48A5, M60A3, M1IP, M1A1/A2 qualified Treadhead..