I've been curious about this as long as I've had my pistol. I've been thinking of putting a cylinder in a vise and putting a fuse (or a rocket igniter) down the flashhole of a loaded chamber to see what would happen.(Outside, of course)
I guess it could be expanded upon by putting a cylinder face down on a 2X4 and doing the same thing and see where it lands, see if it penetrates the wood and what not..But my cylinders are brand new still and I don't want to scuff them up.
If a capped cylinder hits a flat surface, the cap will probably not go off, but if you're at a range, the cylinder might land on a pebble or something else that can contact the cap.
My caps don't fire because I'm not seating them tight enough or my "competition" mainspring is too weak, but with my luck, if I dropped a capped cylinder, it would set off every one of the cylinders.
The best advice? Don't drop it.
I shoot in my backyard, I cap the cylinders and then put them in pouches on my belt and swap them out on my firing line with the muzzle pointed downrange. I live on a XXXX acre plot, there's nothing but soybeans and trees in danger down yonder. I don't store them capped.
I can't believe that someone had the gall to critique his "hot loads". That's downright rude. I hope that guy liked his choice of lube, balls, wads, and powder, if not, I'm sure he would have heard about it, too.