Ok, I have read and watched videos on folks making wax slugs filled with bird shot. Most of these involve cutting the crimp off a factory shell and pouring hot wax and bird shot back into the hull. These slugs seem to work ok but I wanted to try something different. I wanted to make a slug that fit into the wad and crimped in place. That way the slug separated from the wad in flight.
I had an old aluminum cigar tube which I cut down using a tubing cutter. The tube was about the same diameter as a shotgun hull and so the slug would be too big to fit into the wad. I decided to cut a strip of paper measured to the depth of the wad petals. I put a cap on the tube and poured in 400 grains of bird shot. The tubes were placed into a metal pan with the wax. My wax is a mix of toilet ring wax and olive oil which makes it softer than straight paraffin. Incidentally, this is a great mix for wax boolits.
After the wax heats up it fills the mold somewhat so I cut pieces from the side of the pan and put on the top of the mold. Once sufficient wax is within the mold I let cool. If the depth of the wax is the correct depth the slug is pretty much done. The wax cake pops out of the pan and the molds are easily pushed from the cake. The cap is removed, the slug is pushed out, and the paper is peeled from the slug. If the wax did not fill the mold I leave the paper on until the next melt. when I have hot wax to work with I simply fill the top by either dipping into the wax or spreading wax like frosting into the top.
After the slug is complete I peel the paper off and load into the wad. Crimp as usual and you have a good looking shell with no exposed wax. The wax mix I'm using will melt on a hot day. I will make up some more using straight paraffin at some point but for now I'm using up the wax boolit alloy. There is no way I'm using up my stash of primers for wax and hot glue boolits.
Anyway, here's a couple of photos showing the process, albeit crudely. I measure out 400 grains of bird shot and with the wax makes for about a 1 ounce slug. I'm hoping to shoot these next week and update this post with some range photos.