17/25 pdr Pheasant

[motto]

On a more serious note, the question of 25pdr AP versus 17 pdr ballistic performance is an interesting one. The crucial part as I understand it is that kinetic energy i.e. hitting power = Mass x Velocity squared. This means that if you double the mass you have doubled the energy but if you double the velocity, energy is vastly more than doubled.
This is the reason that small arms projectiles have reduced in size and weight over the years as propellants improved and muzzle velocities increased.

David