Wow I'm going to give you some pointers, first of all do that outside with the wind to your back plus a respirator . Wear long sleeve shirt, gloves, plus a face shield . NO, NO, NO. flammables in the area at all. Preheat your( mold) to make it sweat and moisture evaporates .You probably had grease in the socket but also when you poured the lead into the socket not preheated , the moisture came out of the metal. You got very lucky not starting a fire or hurting yourself, be safe my friend, momma will be pissed if you burnt down the house. Use clean lead, this is how I do it just a example. Screen it first then wash out all cardboard, wood, rubber mulch, with the hose on full blast and bucket lying almost level with the ground. All debris will be pushed out of the bucket and lead will remain inside . Make sure the lead is dry before melting I leave mine out in the hot sun and stir it around some, If you going to do this a lot get a Lee lead pot (large one) and buy a piece of angle iron a put some dividers in it for your mold.
Thanks for the info , had no idea it was so toxic, i think of my first 20 years being a mechanic in car dealerships and all the mechanics would blow the asbestoes during brake jobs and fill the work areas with dust, toxic.
Get yourself a cheap muffin tin for molding ingots, they come in different sizes. Do not overheat the lead. If you don't know exactly what you're melting you must wear a respirator in case you have something like wheel weights which contain arsenic. Read up, educate yourself before you continue.
Cast iron corn bread skillet s r great 4 ingots. Used or wal mart rual, rural king ECT new. If u have Any scrap yards around you can buy lead off them too if u need. I pay a dollar a pound. Way to go getting started is the hardest part Properly made ,sized,lubricated correctly cast slugs shoot accurately like any quality rifle copper plated match ammo. Cast ammo and air guns are a perfect marriage. Affordable at home solutions to shoot cost effectively. Check out Elvis ammo on you tube. I learned the most from him. Fortune cookie 45 on YouTube is awesome on all things castings too. Castbullets.com has anything else that you may want to know. Congrats