Unlimited Ammo (Exploit)
Progress through the game to the point where you meet Cassandra, after which the mobile arms dealer should become an available option. You can then get free ammo refills if you call the dealer to your position, then switch to a different weapon. Equip that other weapon, then switch back to the weapon that prompted you to call the dealer in the first place. This process will refill that weapon’s ammunition at no cost to you. Keep in mind, though, that the exploit is likely to be fixed with a future software patch.