From: Ohio, that is all I can say.
Let me try to understand what you are saying. You say that if a shell has less force from the propellant charge, that it will have a larger warhead? I understand the logic there. Less propellant theoretically means more room for the warhead. But I am pretty sure that is not how it works.
The propellant is needed to propel the warhead out of the muzzle. For a given warhead size, mortars would have the least propellant in their rounds, and field guns would have the most. This is because of the required muzzle velocities to achieve the desired trajectory. But by having a smaller propellant charge, you cannot increase the warhead size, because that would mean your trajectory would get screwy due to the greater weight of the projectile.
Now of course, you can add more propellant behind a larger charge to make life worse for the enemy.
Now my personal guess is that field guns of a given caliber have a larger warhead and more propellant than a howitzer or mortar of the same size.
But I think anyone with actual knowledge of the size of these rounds are the only ones who can make the call due to an infinite number of propellant/warhead ratios that all give rougly the same trajectories.
Originally posted by amatteucci:
About the 81mm mortar vs 8,8cm AA gun HE ratings, I presume that the higher value reflects also the fact that mortar bombs are subject to less stress that howitzer shells (that in turn are less resistand than gun shells). So, at a given calibre, a mortar projectile will carry more explosive than an howitzer or gun fired one.