To unlock infinite ammo for a specific weapon, you must first fully upgrade that weapon in all its categories (firepower, capacity, reload speed, firing speed). Once fully upgraded, an 'Exclusive' upgrade option will appear in the shop. Purchasing this exclusive upgrade will unlock infinite ammo for that weapon on subsequent playthroughs. This makes higher difficulties much more manageable and is a great incentive for replaying the game.
Steps to Unlock:
- Fully upgrade a weapon (all stats).
- Purchase the 'Exclusive' upgrade for that weapon.
- Infinite ammo will be available for that weapon on new game+ or chapter select.