Originally posted by MAJ KONIG
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ps. one more note look and see when they invented armor piercing .50 cal ammo and see if they used it in airplanes. you answer will be .50 ball ammo is all they used with the 4 to 1 ratio on tracers.
No they used API bullets as well (almost all a/c mounted MGs had some form of AP or API bullet in a standard load).
However the chances of a .50 call bullet piecing 10mm+ of armour plate at a high angle of incidence after bouncing off a road are pretty damn slim. Whatever the notional penetration of the round you must take into account that
a) It has lost significant energy after hitting the road surface
b) the round has most likely been deformed to some extent by the impact
c) the round will have been made very unstable (it will likely be tumbling or at least is unlikely to be flying exactly nose on).
The RAF and the LW found that AP rounds could be made significantly unstable by passage through a few mm of aircraft skin and this in turn drastically reduced thier armour penetration.
The RAF did a study of tanks knocked out in France in 1944 and found that very few of them had been disabled by a/c (vastly less then claims by RAF and USAAF pilots: something like 5% IIRC), and most of them had been taken out by direct rocket or bomb hits.
I think it most likely that reported kills were more likely to be light or unarmoured vehicles or just complete mistakes.