Why would the 32ACP, 32H&R and several other cartridges be called a 32? The 32-40 uses a bullet in the range of .320-322, other old rounds us these diameters as well and some are larger yet, but are still 32's. But, others such as the 32 short, 32 long, 32ACP and 32 H&R use .313'ish diameter bullets.
So, did 31ACP, 31H&R magnum just sound bad or not roll off well?
I assume there is a historic reason for all of this strange naming, but I am not aware of it. Maybe someone here is...
Matt