Yes, you can call “Activate” on the conditional buttons and then they would send their “Activated Event” if you have the item. And yes, unfortunately you’d need either a conditional button per weapon or at the very least use a slot in the conditional button per weapon and then use Verse to do GetItemCount on each of the slots and it’ll return a value for those items and you can progress accordingly.
You wouldn’t have to detect the ammo, you could just grant a certain amount per elim and set the ammo to “only if not owned” so it doesn’t fill passed a certain point. Also, most situations people want to use this in are 1v1s where the ammo is infinite.