Ive messed with pyrodex a few times (ML  specifically not BPCR) and found it to be only "OK". Big problem I ran into was with compression variations causing some serious inconsistencies regardless of range. The biz about compression is what I fanllay tracked down to and later there was an article in a late '80s copy of MuzzleLoader magazine that also confirmed this suspicion as they found that most of the then available alternatives were very sensitive to compression or lack thereof in comparison to BP proper. The compression inconsitency and effect on accuracy why a little device called the Kadooty was developed and in fact tried in the article.  This widget was supposed to allow one to measure and apply a consistent compression of the powder (through the slug or ball)

As to pyrodex and its other issues, Im reminded of a ML pig hunting trip at  Ft.Hunter-Ligget in CA where a friend had a new Kodiak that he was using pyrodex in. At the end of the day we had to unload and used the typical CO2 unloaders, we hear a kerthwap! at a tree and in looking to see iffen the slug was still useable we find a perfectly formed to breech slug of  pyrodex the load... 

The rifle had been loaded in the evening prior to the days hunt but left uncapped until we hit the field so it was exposed to no more than a 24 hr time at what ever the relative humidity was over night... Sorta said something to me and the others I was with. Next time out the Kodiak owner was using Goex 2f...   

D.