Gunsmithing does not grant the ability to craft firearms, ammunition, or black powder. Rather, it allows the purchase of bullets, pellets, black powder, and alchemical cartridges (with 1 rank in Craft [alchemy]) at the listed reduced price, but does not grant a discount on the purchase of any firearm. Resold items gained through this feat are worth half the actual cost paid, not half the regular market value for the item. No PC can purchase a gun without this feat, even if they possess the Amateur Gunslinger or Exotic Weapon Proficiency (firearm) feats.
A parte que responde especificamente à sua pergunta está em negrito