Noah, I suspect that biting the bullet is more expression than fact, for reasons discussed earlier, like where are they supposed to come from and what about the threat of swallowing and weren't there objects that would work better.
But that's just opinion. As far as actual tooth marks on actual bullets, I can state as an incontrovertible fact that the common gray squirrel will happily chew on a minie ball.
There's no citation here, just first hand observation from perhaps one of the few people you know who ever had both in his study at the same time. If I remember, I'll show it to you the next time we run into each other.
Her name was Jenny, which also happened to be the name of Karl Marx's wife, but oddly enough that was just coincidence.
M. A. Schaffner
Midstream Regressive Complainer