[sdiy] sort of OT: bullet ricochet noise?

[anthony]

Does anybody know? What causes that motor-like noise when a bullet 
ricochets? Is it the bullet spinning really fast? Is it similar to what an 
airplane sounds like when it's in a divebomb maneuver? If you've never heard 
that, just go camping in Alexander Springs in Florida - unless they've shut 
that training facility since 1990. Scared the bejesus out of me - no one 
told me a bombing test range was next to where we were camping. Still, the 
Springs are worth it. Watch out for the gators! They're fast motherfuckers!