If the question is how do I run this in a game?
Then the answer is that if the players raid an ammo dump of the right tech (Clan or IS), it is magically the right kind of ammo they need; 60mm Irian SRMs, for instance. If they try to salvage ammo in a BT campaign then untouched ammo tons are good to go, but partial tons are lost, but everything is still the right kind of ammo, assuming tech compatibility.
In an RPG, I make it more granular, but many types of the same weapon can still inter-change.
Had TPTB never made Ultras and LBX and standard autocannons have different range performance and non-interchangeable special ammo, I would long ago have head cannoned that autocannon "Ammo" was all the same. But now, with the moves to standardize the art, we can even see a move to big-bore LBX and rotary-barreled ultras. No chance for consistency in ammo there.