From X3 Wiki
Ammunition Factories are produce Mass Driver Ammunition from Energy Cells, Ore and Food.
NPC stations will buy Teladianium as a secondary resource.
This factory complements a Mass Driver Forge by creating and distributing ammunition for the Mass Driver weapon. It sells the ammunition in cases of 200 rounds each.
This factory is devoted to the creation and distribution of Ammunition for the Mass Driver weapon.
Projectiles are created for hardened steel, which is produced on the station. Each projectile is then put into feed crates that are sold and are placed directly into the Mass Driver weapon system.
This factory is exclusive to the Argon and Split.