I had a battle open when reloaded the ruleset. The tanks in battle (HT Railguns to be precise) had full aux ammo. Upon returning the aux gun ammo was returned as main gun ammo.
If the game is reloaded from the geoscape, then vessel launches and lands, the aux guns magazines are empty. One can still manufacture aux gun ammo but it is not used when deployed in combat.
The main guns fire as normal.
God damn it, so this bug was never fixed :/ I guess it's either back to unlimited ammo for secondary weapons, or maybe it'll be possible to fix with some MAJOR code juggling and trickery. Grr. I need to conduct tests of my own, too...
EDIT: There is a convoluted way of circumventing this problem:
1. Make tank ammo a normal ammo item;
2. Enable tank Inventory screen. You will only have access to that inventory at mission start & through scrolling through soldiers - inventory button won't work.
3. Load up tank weapons manually.
4.
Not sure yet if these weapons will be reloaded next mission, or if you have to load the tank manually every time.
5.
Possibly the tank ammo clip will be gone, even if you don't fire a round
6.
Not sure if you put anything in tank's inventory, it will be recovered or destroyed - don't know if this has been fixed, how does it work with dogs?
Of course this also means tanks will be possible to reload mid-mission, bug, feature?
EDIT2: Ain't gonna work. You always get 'refund' on ammo from the 1st weapon. So if you have, say, a normal 360-round clip on the tank MG, and fire 4 rounds, you will get 'refunded' 356 tank MG ammo clips. I guess there is no way but to either get rid of secondary weapons, or make them unlimited ammo, or... remodel tanks into wearable 'armor', in other words - vehicles
I will experiment with that.
EDIT3: 2x2 crewed armors won't work properly. The game doesn't count the space they occupy, and if you take too many, it bombs out. Plus it is impossible to change movement/death sounds... I guess there's only one fallback left - unlimited secondary ammo. Gah...