Enter the world of hypothetical-ness:
Imagine a world where we have used almost all of our copper, lead, and iron supplies and deposits. The amount that we still do have is not enough to make a lot of bullets and military ammo.
But what if we could use glass as a projectile that could be shot from a gun or military weapon? What type of damage would it do, how would it change warfare, and how would cities change, and what would be the economic effect (i.e, now they are making glass in large amounts, how would that change the economy and areas with high amounts of sand, soda ash, and limestone)?
EDIT Also there is no way to recycle the metals: copper, lead, and iron.
What damage could it do?
How would it change warfare?
How would cities change? (Defense)
What would be the economic change in areas with high amounts of sand, soda ash, and limestone?