:shake: From these replies, home-made caps do not look promising - but has anyone thought about carefully substituting small bits of the white tips of strike-anywhere matches?? (Are strike-anywhere matches still made ??)
I'm reluctant to share this with younger generations, but if you're reading this, you're probably not a detonation-dummy. In elementary school (1936-1941), we cut off the tips and compressed 6 or so in a heavy steel nut between 3/4" dia bolts slowly screwed in from either side! Hurled against the brick side of the schoolhouse - BOOM! Today, cops would be there in 3 mins. Don't ask me how, but often one of the bolts would fly loose. Don't ask me, either, how we survived those dumb stunts.