Casting Round ball (sometimes referred to as "Runnin' Ball) for use in muzzleloaders is a simple process which requires a little, readily available, inexpensive equipment (shown above). As in all other matters related to the sport of muzzleloading, safety should always be your first concern and safe conditions for running ball are easily accomplished.
In order to cast safely, we must remember that lead is a toxic, heavy metal which vaporizes when melted. Once vaporized, it can be inhaled and so enter the blood stream, giving rise to higher blood lead levels than is healthy. In order to prevent this, ALWAYS cast outdoors. The casting setup you see above was set up on an iron table in my backyard.
I addition to casting outdoors, be sure that you melt your lead on a dry day and in the complete absence of not only rain, but other liquids, such as coffee, soda, etc. Mixing such liquids with melted lead can create a very impressive spatter of melted lead and should this spatter come in contact with any part of your body, you're going to get burned.
Finally, in order to prevent being burned while casting, ALWAYS wear safety glasses, a long sleeved shirt, long pants, shoes, sox, etc. There is some debate on the subject of gloves. I wear work gloves while casting. Others fear hot lead pouring into their gloves, so they avoid them. You decide which way you feel safer but should you opt to wear gloves, be sure they are tucked into your shirt sleeves so that any spilled lead will stay out of the gloves.
So now that we're safe, let's cast.
First, we need to find a source of cheap lead. Telephone company workers, plumbers who work in areas with old homes in them, and scrap metal dealers are good places to look for cheap lead. When you find some, buy a couple of hundred pounds and find a home for it in the garage. It'll come in handy some day. You'll need a way to cut your lead up before melting it down, so unless you can think of a good method (hatchet, hacksaw, etc.), try to find lead that is easily cut, like sheet lead. Don't get overly compulsive about the softness of your lead. I use the old thumbnaiil test when I'm buying lead. If I can make a mark in the lead with my thumbnail, it's soft enough for me. Mind you, you can dig your thumbnail into some pretty hard lead if you put your mind to it, but harder lead makes for a useful hunting projectile anyway.
When you've found a source of cheap lead, bought some and brought it home, clean it thoroughly. There's enough in the way of impurities in lead so that you don't want to have to deal with some of the stinky crud that will come off old plumbers lead. Get the crud off before getting started. A stiff brush will come in handy here.
When you've found your lead, cleaned it, and cut it up in small enough pieces to deal with, you're ready to cast. Take note here that if your pieces are still fairly large, it would be a good idea to buy yourself an "ingot mould" and melt your lead down in either a large melter, or in a simple pot set upon a hot fire. Put your lead in your melter or your pot, and ladle it out into your ingot mould. (Lyman makes good ingot moulds.) You can see four lead, one pound (each) ingots I made in the photograph above.
In order to get started with casting, you'll need an easy to handle melting pot. You can use a larger electric, ten pound melter that pours from the bottom such as the Lee Production Pot IV, which has four inches of clearance between the spigot and the base. That's what I've been using these days. A simple, electric, four pound sinker pot (like the one in the picture above) works too. I used one of these for many years. In absence of either, a small pot that you can leave on a hot fire long enough to melt lead will also work. You will need a ladle if you chose to melt your lead this way and you will ladle the molten lead from the pot into your bullet mould. An electric pot is easier and they're cheap to buy.
As you can see in the picture, I set my "melting pot" in a metal tray, which is set within another metal tray. Both trays have rims so that in the event of a spill, the hot lead isn't going anywhere. Set the outside tray upon a small table that is comfortable to work from and set yourself in a comfortable chair in front of that table. Turn the heating element in the pot on and melt some lead. Melting a pot of lead will take a little while. If your melting pot has a temperature gauge, let the lead get hot, but not very hot. As you begin to cast you will learn to approximate the proper temperature. In the beginning, just try setting your temperature gauge in the middle.
When the lead is properly melted, you will need to "flux" a bit. I use bees wax for flux. Other fluxing agents can be purchased in any good gun store. Fluxing will help purify your lead.
In order to flux, when your lead is melted, drop in a bit of fluxing agent. Use an old spoon, like the one you see in the picture, to stir the flux into the melted lead. When the mixture has been well stirred, spoon whatever crud floats to the top of the lead off and throw it away. You are now ready to cast.
A number of companies make round ball moulds and muzzleloader bullet moulds in various sizes. The mould you see in the picture is a .530 round ball mould made by Lyman. Lee makes a less expensive aluminum mould of adequate quality too.
Pick up the mould and pour some of the molten lead through the small hole in the top with the "spru cutter" of the mould in place.
Hold the mould handles together for a few seconds and use a "knocking stick", like the one pictured, to push the spru cutter off the top of the mould. Hold the mould over a small piece of cardboard, like the small cardboard box in the picture, and open the handles of the mould. If the ball does not immediately drop out, use your knocking stick to push the ball out. For this purpose it is a good idea to drive a nail through one end of your knocking stick so that you can use the nail tip to push the ball out of the mould.
Don't expect the first dozen or so balls you cast in a cold mould to come out perfect. Throw them back into the melting pot until balls do begin to come out perfect. If this isn't happening in a reasonable length of time, adjust the temperature of the melting pot.
After you have a few perfect balls in your cardboard box, dump the balls into an aluminum pie plate like the one pictured. When you have cast 100 ball or so, let them cool and examine each carefully for flaws. If there are no flaws, dump the newly made and examined balls into a small bucket of some sort as finished ball and put a note in the bucket with the size of the ball on it.