| My Self |
Gunsmithing Feat wrote:
Crafting Ammunition: You can craft bullets, pellets, and black powder for a cost in raw materials equal to 10% of the price. If you have at least 1 rank in Craft (alchemy), you can craft alchemical cartridges for a cost in raw materials equal to half the price of the cartridge. At your GM’s discretion, you can craft metal cartridges for a cost in raw materials equal to half the cost of the cartridge. Crafting bullets, black powder, or cartridges takes 1 day of work for every 1,000 gp of ammunition (minimum 1 day).
I'd say gold and a full day. It doesn't reference Craft (alchemy) as needing a skill check to craft, and it gives its own time and price to craft ammo.