Roskoe,

In your example of the tungsten versus aluminum bullet, they'll have the exact same shape, as you cited, but they won't have the same ballistic coefficient.

The reason is because the ballistic coefficient of a bullet is dictated by the bullet's sectional density, and the sectional density is the ratio of the bullet's diameter to its weight.

So the tungsten bullet will have the identical shape as the aluminum bullet, but will have a higher ballistic coefficient due to the higher sectional density.