I just found this formula for percussion caps. No lead, but it does have antimony. The interesting thing here is that you cam make potassium chlorate much easier than you can make a fulminate.
17 grains of Potassium Chlorate
9 grains of Antimony Sulfide
3 grains of the Sulfur/Sodium Bicarbonate powder
4 grains of fine sand (passes through a 40-mesh screen).
Impact sensitive explosives, sounds like fun but well outside my comfort zone. I’ve accidently set off a primer before, hate to think wat would happen with a pound of the stuff.