Germans put a CAS fighter in the air with half that power available to it.
Do you mean late war 75mm Bordkanone? It is from quite different league from what you propose penetration wise, weighed "only" 750 kg as it is not made for great AP. And It was fitted only on bombers that were designed to carry that much weight (+me262 with jet engines)
As from 80 to 78. Intelligence. They aren't going to expect a smaller round of doing far more damage to their tanks and such.
Yay! At last you made one reason. It is from "our enemies are idiots" category, but still, congratulations
I guess your ego doesn't allow to make even the smallest change to your design, that's a real answer on the question why
that so far you've all ignored the supply line results of what you've done and things have worked out fine
Ignored is simply
untrue. If you ignore those things, that doesn't mean that other's do, too
We designed several variants of 40mm guns not 40mm, 38mm and 41mm guns
SVA-10s, mosins and Patriotism use the same round
Sniper rifle and heavy machine gun use the same round
Our Alexi frigates use the same turrets as our AA tanks
We try to use as few different engines as possible and so on
[bAlexandria[/b], even if we'd share same calibers as our enemy (We don't, Capia uses 50mm, 75mm and 100mm cannons. and Moprovia 60mm and something else) our own supply lines are much more important. Besides ability to use ammo of the enemy is always a double-edged thing
Guys, just tell me why real world armies prefer to have same caliber for everything? From flaks to tank guns, to howitzers to naval guns
Tell me why Russians used different kinds of 7.62 for vast majority of small arms until AK-74 appeared (and no, it is not 7.5)
Tell me why NATO has 4 standard chambers for small arms sinse 1950s (3 of 4 existed long before and was used as standard in different armies)
Why the hell real world armies make guns compatible with 100+ year old ammunition if it is "outdated"?
Why the hell modern high tech howitzers use the same caliber as WW1 one?
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Do you release that our curent K-1s use the 80mm gun, right? As well as half of the Navy? As well as several hundreds in artillery role? And no, you can't switch it all to the new gun in a moment, without disrupting production when we need stuff produced NOW (And destroying existing weapons midwar just because they are a bit outdated is an idiotic decision)
Now, We'll need to produce both 80mm and 78mm shells just because you are stubborn. Hope GM will punish for that
PS, 80mm and 115mm artillery fill different roles, one is light another is a medium artillery piece, thus one can't replace another