Gents,
Great topic. I think the clarification has been given now regarding the amounts of artillery ammo, its replenishment and how it gets depleted. I would like to focus on the discussion of possible upgrades to the logic.
First, I think that the ammo levels should be added to the OOB files by unit based x shots by unit or the number of shots per gun option.
Secondly, I think that artillery should be supplied by caisson wagons, like a suppy wagon, instead of having a pool of shots to draw from.
I've played a scenario where my Rebel friend had run out of ammo but I captured his gun and fired upon him. My units were nearly at the other end of the map and couldn't of supplied the the guns but...*puff!*..the guns were fully stocked and firing on the enemy.
I don't agree with the fact that infantry can fire endlessly, if the dice are in their favor, throughout a battle or that a unit goes low ammo on their first shot of the battle.
This is why I think the ammo levels should be added to the OOB file by unit. Adds more realistic behavior and supply can be distributed to the areas of use. Also, a captured gun would only have the ammo level it had when captured and not instant shots from a pool of shells far away on the map.
That' my old 2 cents to this topic. Would love to put this together as a formal request to JTS ACW series for possible updates to the games. It would need support or signatures to gain some steam.

Happy 4th of July to all!