Hey all. New here to the forum but I first found this page about 2
 years ago. I had just discovered the use of the sling as a weapon
 and - was surfing the net for info on technique etc. - found the info
 on this site very useful and it made me take a giant leap in my know
 how on the subject. Thanks to you guys for that. Here now I'm
Still no expert but I can hit what I'm throwin at most of the time.  
I,ve tried various projectiles from concrete to clay, lead and stone.
I recently bought a .690 lead round ball mould from lee precision and
 it makes a great bullet. Most tire shops around here will give away old
 tire weights. I melt these down into ball rounds and they throw like  
A rocket. (On a side note .690 is the proper size for a 12 gauge shotgun
I handload these ball rounds for hog huntin, but that's another matter)
I have also used with moderate success plaster moulds for casting lead.
Take a small cardboard box about 3 inches by 4 inches or so. You need  
A model for your casting. I used a 1 1/2 ounce lead egg sinker for  
Mine but I bet you could use clay also. Mix the plaster and pour the box  
Half full. Coat the sinker with a light coat of vasoline and insert. It  
Halfway WIDTHWAYS into the plaster after it hardens enough
That the sinker won't sink into it. Let this dry for 24 hours. Then
Carve a few key slots into the top( what will become the inside) of  
the mould. These need not be much deeper than 1/4 inch by 1/4
 inch or so. They wil aid in aligning the mould blocks when using it.  
Put a light coat of vasoline on the top of what you poured
 yesterday. Too much and the blocks won't fit together properly.  
Too little and you won't be able to get the blocks apart when dry
Pour the box the rest of the way fill and set it aside for another
24 hours. Peel the cardboard off and CAREFULLY seperate the blocks
The plaster will still be a little soft. Take a knife, small chisel or  
Flat blade screwdriver and carve the groove in both blocks that
You will pour the lead through. These need not be wider than 3/16  
to 1/4 inch. Set the blocks aside for another couple days to dry.
You will notice a texture and hardness change in the plaster when
It is completely dry. I have gotten about 50 or 60 castings from these
Before. They become unusable. Happy slinging.

Hi, leadrocks;
   Welcome to our forum.  Thanks for all that info about casting lead.  Obviously, it's something you've done quite a bit of.

Quote from xxkid123 on May 1^st, 2010, 11:40am:

 
I'd be honored. Thanks.

Here's a pic of my old plaster mould. You can see what eventually rendered
It unserviceable. From repeated exposure to heat the plaster slowly chipped  
Out around the edges. The 2 dimples on either side are the keyslots that  
Made the blocks fit together securely. I also made dog ears on the corners  to
Help the blocks fit but I don't think they were necessary.  I used clay to fill in  
A few of the chips in the plaster. That's what the dark smudges in the cavity
Are.

I just found one of my 12 salvaged 40MM inert and spent Mark19Mod 3 grenade launcher machine gun rounds. I forgot all about them for years.  
I will get a pic up later, but the thing is made of aluminum and is 40MM in width. I dug a bunch out of a berm way back when I was a full time Leatherneck armorer. The ones that hit the practice tank were painted onto the side of the tanks armor. I'd like to get a mold of it and cast more with your process, but maybe lead would be too heavy for such a gigantic round.

Here's a drawing of my mould. It's very simple, just some white concrete on a container.  
I made a bullet with modeling clay and let the mould dry. You have to use something soft and maleable for the bullet shape, otherwise it gets stuck forever.
 
Then, I scrapped the modeling clay and that's it. I use an electric stove like the ones you take for camping to melt the lead.

Here's another one of a 1 1/8 oz ball stuck over an inch into my 3d deer
Archery target. Greek throw at 20 yards.

Quote from leadrocks on May 19^th, 2010, 5:17pm:

 
I suppose that target is somewhat similar in density to actual muscle. Good shot, you achieve penetration with a sphere ammo.