It isn't. In terms if destroying OBJ's, the HE rounds from aircraft cannon offer 2 distinct advantages over the the FMJ fired from an MG. First, cannons offer about 4 X's the amount of damage per round and secondly if you miss with cannon fire you may still damage the OBJ thanks to splash damage. Sure, rates of fire and ammo load mean something but in terms of how they are dealt per round there is a difference. Also, ordnance offers even more damage and an even bigger area of effect for splash damage.
I do not know how HTC has things coded, but it appears that vs OBJ they use a "lb" value for each round, rocket, or bomb. Take that vs the "hardness" of the OBJ and you can determine how many rounds it takes to destroy that OBJ.
I think it would be a whole lot easier for HTC to simply change the hardness settings for the different OBJ's and be done with it. I mean seriously, an ammo bunker made of reinforce concrete gets the SAME setting as barracks made of canvass and plywood???
I'm aware of all this, but you miss my point.
.50 cal is not even the same
type of damage as a cannon shell in real life. You would have to shoot clean through a beam with an MG to break it, but with a cannon, a few rounds, or with a 30mm, even 1 or 2, might suffice, due to the explosion.
Where a .50 will punch through some concrete, and make a hole, a cannon shell is going to blow a fair sized chunk out of the wall.
Its more than just ammount of damage done, and blast radius, and simply adjusting the hardness will affect cannons which
could do some real damage.
Take the BK 5, for example. It fires an HE round, and so doesn't penetrate a whole lot of armor. If you bump up the hardness, theres a chance it might start bouncing rounds off the dar tower, or bunker.
Or the Mk 108. It fires a shell large enough to do some not inconsiderable damage to a concrete wall. But it penetrates very little armor due to being both an HE round, and having a low velocity. Bumping up the hardness would unrealisitically and unintentionally nerf the 30mm as well.
The reason is that concrete is not the same as a steel bar, which is not the same as armor plate, which is not the same as a wooden flight deck.