Everything had to be calculated by hand and tested. We did not know much about mach 2 plus in that era. But we could make bullets that could hit that speed easily so everything that needed to go fast was that shape.
22-250 Remington ammo can reliably hit 3.4 - 3.6 mach
Look familiar?
Funny enough we have made gun ammo that can hit Mach 29+ but it has little use out side of understanding space impacts. They look really funny