That's really interesting. I have a single Kynoch .450 #1 Express (BPE - I assume) round with copper tubed paper patched lead bullet. The tube is 2/10" in diameter at the nose of the bullet. I assume it is a 2 3/4" .500 case, necked down. I have not, nor will not take it apart, being the only one I have.

Just about anything it impacts will detonate the priming, Huvious.

Compound merely sifted into the hole, then covered over with beeswax works.

With .22 Stingers, a single shot will cut off a will, a bit more than 1" in diameter. 3 shots with them in an 1863 Springfield Rifled musket would cut off a 10" Aspen.
Fun stuff - however BEWARE!! Homeland security might not like this 'stuff' much at all.

The formula was 5:1:1.

5 parts potassium chlorate, 1 part sulfur, 1 part charcoal.
I used drug store Potassium Chlorate, sublimed sulfur(flour of sulfur) and ground up charcoal briquette's which are not charcoal at all. Perhaps these chemical changes lent some 'stability' to my mixture. Also, the sublimed sulfur is much more highly refined than what was used 'back then'- which might make the mixture even more hazardous to your health.

This formula was printed in H., Logan's book "The Pictorial History of the Underhammer". It is the formula used for the pill and tube locks of the early 1800's.

Apparently this formula was outlawed in the UK in the late 1800's as if amalgamated slurry, when dry, became difficult to handle safely. I did not know this at that time. Seemed fine to me- and to everyone throughout the period of it's use - until outlawed, that is. That is why the "BEWARE!"