That has already been considered and compensated for. Traders will only have ammo 20% of the time. The only ammo that will always be available (although I'm considering even making this very limited) is 9x18mm ammo. HAH! That'll stop all you cheating gits from trying to "work around" the pressure and worry of running out of ammo
ED - Ok I didn't like the thought of even 9x18mm ammo being easy to get hold of, but so things aren't totally unfair the chances of being able to buy 9x18mm ammo is better than all the others (40% vs. 20%) The Zone is supposed to be a wasteland after all, not a supermarket!