I won't answer the question because it's not only hypothetical and ridiculous, it's impossible.
But keep digging, it's the one thing you're good at.
OF course it is hypothetical. And of course it is ridiculous - nobody in their right mind would choose a flattened BB at whatever velocity over a heavier bullet of the same diameter and velocity, even if both would expand to the same diameter. Because mass matters.
If mass did not matter, the flattened BB would be equally effective.
So keep dodging - it just confirms you know you are wrong. Velocity is not the only thing that matters.
