Vette. I think that about the only way you could do that would be to get a really big pile of coals going and have the pot literally be buried at least half way into them. Of all the metals used in casting, lead takes the highest temperature to melt. (OK. I know it takes more heat to melt antimony, but usually you'll be using it already mixed in an alloy of some sort which melts at a lower temp than lead. All your bullet alloys will melt at a lower temp than pure lead.)
The idea of a camp stove or turkey fryer is a good one. I think the fryer would be faster, but the stove will work. I recently bought a turkey fryer just for the purpose of cleaning wheel weights when I get large batches as the Coleman stove was too slow to suit me. (Important when cleaning 100 pounds or more of wheel weights or range scrap.)
One thing that will help while you're melting that big chunk down is to plat the flame from a propane torch over it. heats that block up faster.
If you don't have one, contact Bill Ferguson (
www.theantimonyman.com) and buy a lead ladle from him. They don't cost all that much, and it will speed up pouring that lead into your ingot molds. It's a hell of a lot safer than trying to pour from the pot too.
Paul B.