I can't get black powder, so have been using Pyrodex in a 36 cal Remington cap and ball revolver. When cleaning the cylinder the other day I noticed some gritty black residue in the sink and was reminded of something I had read in a "Safety Data Sheet" for the ingredients of Pyrodex.
Potassium nitrate - 15-40%
Potassium perchlorate - 15-40%
Silica: crystalline quartz - 0.5-5%
Distillates, etc - 0.1-1%
Quartz has a relative hardness of 7, whereas steel is around 6. When Hodgdon was contacted their reply was: "Hello Bill, thank you for contacting us. I reached out to our chemical engineer on this question. He said the quartz composition was not something we could share details on but it should not be a concern. He said the flame temperature would have a much more significant effect on barrel life and that Pyrodex would have a lower flame temperature than real black powder and a barrel would be expected to last as long or longer than one used with black powder." My question concerning the reason quartz was included was not addressed. I can see why finely ground glass(quartz) is used in primer compound where the added friction enhances ignition, but why in Black powder substitute? Maybe we should consider Pyrodex for lapping barrels.