It is an interesting idea but I was just trying to follow the thinking of the day linearly.
I don't think you could get more than 150 to 200 fps or so more velocity in a 3 1/2 dram paradox with a round ball and you can't harden them. Leslie Taylor was quite an inovator and ballistician,Foresythe notwithstanding. Probably going to come down to lighter bullets higher velocity vs heavier bullets with a higher sectional density. I would like to try a ball in a 10 or 8 bore paradox gun.