Bladestorm: The Hundred Years’ War Cheats
With any unit that has ammo (Archers, Javelins, Throwing Knives etc etc…), wait until you are out of said ammo.
Press X to back out of the unit, and wait for the AI to shoot of their own accord.
Re-join the group, and you should have ~10 more ammo. (Not a full restore). When you run out, just leave the squad, wait, and re-join. It can be done infinate times.