So for example, let's say there is a ''Special Ammo'' perk for the Soldier, would 1 point in it give ex: Armor Piercing Rounds, while 2 points give Explosive Rounds, and removes the Armor Piercing effect? (if explosive does'nt have that, but greater)
That'd be nice
Also, this was really off-topic
Well, there's no confirmation that there are even more than one type of special ammo. The only thing we have is Richard Ham saying "Today, Jolly is handing out Armor-Piercing ammo." which implies there is more than one type of upgraded ammo.
There are two ways i can see the skills working. its possible tat there are several types of ammo with different buffs, and each is a different floating skill that soldiers can take. Or it could just be upgrades for the resupply skill, in which case, the ammo types would most likely just be +damage.
To explain with an example, there might be AP ammo that goes around damage reduction, explosive rounds that have a small AoE, and incendiary rounds that set people on fire. Or there might just be the base restock ability, put a point into it and get AP ammo for +5% dam, another point for FMJ rounds and +10% dam, a third point for TMJ rounds and +15% dam.