If the bullet is large enough to begin with, expansion is just icing on the cake. No?
I realize this has little or nothing to do with this discussion, but I would opine that shape and size of frontal area of expanding/expanded projectile matter more (along with speed of moving projectile) than does the diameter of the original bullet. Of course the original diameter may affect those details.
Sometimes, the air you 'let in'matters less than the air you 'let out'.
