(From SWAT_Corac in the comments, pinned here for better visibility)

Below is something That should help some people that are wanting this but dont want everything crafting off the same material. OR you want to make it so that people on your server cant make the rockets. You can adjust as needed. Example and the Full ammo names so you can change it for each one. This will go in your Game.INI


ConfigOverrideItemCraftingCosts=(ItemClassString="PrimalItemAmmo_AmmoFactory_AdvancedBullet_c",BaseCraftingResourceRequirements=((ResourceItemTypeString="PrimalItemResource_Metal_C",BaseResourceRequirement=2.0,bCraftingRequireExactResourceType=False)))

PrimalItemAmmo_AmmoFactory_AdvancedRifleBullet_c
PrimalItemAmmo_AmmoFactory_AdvancedSniperBullet_c
PrimalItemAmmo_AmmoFactory_Rocket_c
PrimalItemAmmo_AmmoFactory_SimpleBullet_c
PrimalItemAmmo_AmmoFactory_SimpleRifleBullet_c
PrimalItemAmmo_AmmoFactory_SimpleShotgunBullet_c