I’ll let you take care of the fulminate of lead (what is currently used in most primers) at your place. Toxic, touchy and dangerous to deal with on an industrial basis.
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).