Like many others, I tried very hard to make BH209 work in my KRB. I got constant hangfires with it, even after drilling out the breechplug. The only way I could get instant ignition was by using a duplex load, with about 5 grains of FFFG Goex blackpowder dropped down the bore before the BH209 charge was dropped. It worked and shot accurately and left the bore as clean as with BH209 alone.
At this point I have reserved my KRB for iron sight use with blackpowder and heavy lead conicals, and it is a dandy rifle for that purpose.