Something Obvious

There's a long running myth that fighters bounced ricocheted .50 BMG off roads and through the belly armor of Nazi tanks.

Let's test with GURPS!

.50 BMG does 6dx2 pi+.  .50 BMG AP does 8d+1(2) pi.  API does 8d+1(2) pi inc.

Penetration from an average roll are 42 DR and 58 DR respectively.

That's also penetration at 0°.

UPDATE: I simply cannot find my reference for the belt composition used by the fighters.  So I have removed mention of what combinations were used.

The most common Nazi tank when Mustangs are strafing targets of opportunity is the Pzkw IV, with belly DR of 40.  Panthers and Tigers have thicker skins underneath too!

Just barely penetrates if it was a straight shot.

But a ricochet would be at an angle that doubles the DR and even a max roll of 72 isn't punching the, now, 80 DR of the belly.  API with a max roll will get 9 up through a Panzer IV's belly, but now we have to consider that it's lost a lot of velocity from the ricochet and the hit on the road likely triggered the incendiary charge before it hits the bottom of the tank.

I'm going to say Myth Busted.

Especially since our Armor Lord and Savior The Cheiftan covered this very topic and it falls under "other lies told by fighter pilots."