Is the formula that Tony Williams uses to calculate power valid for large calibers like 50mm? As seen on
this page, it works like this:
Damage = projectile weight (kg) * muzzle velocity (m/s) * (1 + (projectile weight's explosive % ÷ 10 ))
I guessed the last one because that's what it seems to be (ignore the black one, it's wrong from a typo):
This formula leads to table 1 on that same page of Williams', where that power value's divided by 10 and rounded up, giving e.g. the .303 and MG17, MG151/20 and Hispano, NS37 and MK103 power values of 1 and 1, 16 and 20, and 106 and 99 respectively. If we apply this same method to the 50mm BK5 projectile that's 1530g with 335g explosive content and 835 m/s muzzle speed (
as per this page), it gives a power of roughly 280.
That seems a bit large, and somehow a linear addition of (1+HE%) as coefficient to kinetic power doesn't seem natural.
