There are recipies online for ballistic gelatin.The ingredients can be found in the grocery store.
Here is how you make it..
Gather your equipment and materials. You will need 100% pure gelatine, distilled water, a large pan, a whisk, a strainer, a thermometer, paper towels, molds, space in the fridge and a heat source.
You can estimate how much gel you will need to fill your molds by filling them with water. It takes roughly 1 pound of gelatine powder per gallon
Heat the water to 150 degrees, remove from heat. SLOWLY whisk in a 10% ratio (by weight) of gelatine powder. The pan needs to be large enough to contain the foam that will form
Put a paper towel in the strainer and filter the gelatine through into your mold(s)
Place the molds into the fridge and allow to chill completely to 35 - 40 degrees. (24-30 hours) Large blocks of gelatin require more freezing time than smaller blocks of course so you will have to estimate according to your mold size.