I found a good bolg on “Building a Furnace for the Home Foundry” http://www.rotblattsculpture.com/Articles/buildingabronzec.html
We discussed casting bullets from copper, zinc & other metals. This furnace will deliver enough heat to melt 20lbs. of metals.
Do not use a propane tank or any other tank that was used for flammable material to make your furnace.