There aren't a lot of feats focused specifically on ammunition. Here are some ideas. Feel free to offer any tweaks or suggestions for improvement.
Ammunition Salvager.
Prerequisites: Craft (Weapons) skill 1 rank.
Benefit: Choose a certain type of ranged weapon (other than firearms or siege weapons) in which you are proficient and which requires ammunition, such as shortbows or heavy crossbows. As long as a supply of relevant raw materials is readily available, such as wood for arrows, or stones or metal for slings, you may make a Craft (Weapons) skill check to repair ammunition of the chosen type that has been destroyed or rendered useless. The DC of the Craft skill check is equal to the normal DC for crafting new ammunition of the given type.
Normal: Generally speaking, ammunition that hits its target is destroyed or rendered useless, while ammunition that misses has a 50% chance of being destroyed or lost.
Special: You can gain this feat multiple times. Its effects do not stack. Each time you take the feat, it applies to a new type of weapon. Magical and masterwork ammunition repaired in this way does not retain its magic or masterwork properties, but when repaired becomes an ordinary item of ammunition of its type.
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Ammunition Hoarder.
Prerequisites: Craft (Weapons) skill 5 ranks, Ammunition Salvager with selected weapon type.
Benefit: Choose a certain type of ranged weapon (other than firearms or siege weapons) in which you are proficient and which requires ammunition, such as shortbows or heavy crossbows. Ammunition crafted by you for the selected weapon type is only destroyed or rendered useless on impact on a critical hit, and has only a 25% chance of being destroyed or lost on a miss. If the ammunition is masterwork quality, it never destroyed or rendered useless on impact and has only a 10% chance of being destroyed or lost on a miss.
Normal: Generally speaking, ammunition that hits its target is destroyed or rendered useless, while ammunition that misses has a 50% chance of being destroyed or lost.
Special: You can gain this feat multiple times. Its effects do not stack. Each time you take the feat, it applies to a new type of weapon. This benefit does not apply to magical or masterwork ammunition of any type.
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Ammunition Forager.
Prerequisites: Craft (Weapons) skill 10 ranks, Ammunition Hoarder and Salvager with selected weapon type.
Benefit: Choose a certain type of ranged weapon (other than firearms or siege weapons) in which you are proficient and which requires ammunition, such as shortbows or heavy crossbows. The ammunition available for that weapon is considered unlimited as long as a supply of relevant raw materials is readily available, such as wood (for arrows or bolts), stone or metal (for slings and halfling sling staves), and so on.
Special: This benefit does not apply to magical or masterwork ammunition of any type.
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Ammunition Specialist.
Prerequisites: Craft (Weapons) skill 15 ranks; Ammunition Forager, Hoarder, and Salvager with at least one weapon type, plus Ammunition Hoarder and Salvager with at least two other weapon types.
Benefit: The amount of time you need to create or repair any ammunition using the Craft (weapons) skill is reduced to 3 1/2 days from one week’s worth of work, or to 8 hours from a full day’s work of 16 hours. If your Craft (weapons) skill check result × the DC equals double or triple the price of the item in silver pieces, then you've completed the task in one-quarter or one-sixth of the normal time (14 or 10 hours instead of 3 1/2 days, or 4 or 3 hours instead of 16 hours).
Special: This benefit does not apply to Craft skill checks made to create or repair magical or masterwork ammunition of any type.
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Ammunition Mastery.
Prerequisites: Craft (Weapons) skill 20 ranks, Ammunition Specialist, plus Ammunition Forager, Hoarder and Salvager with at least three weapon types.
Benefit: The ammunition available for any weapon requiring ammunition (other than firearms or siege weapons) is considered unlimited for you and your party as long as a supply of relevant raw materials is readily available for that ammunition, such as wood (for arrows or bolts), stone or metal (for slings and halfling sling staves), and so on.
Special: This benefit does not apply to magical or masterwork ammunition of any type.
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