A couple of things to remember.
#1 The pressure is 15% less with the same load as 777.
#2 The higher velocity is due to peak pressure being maintained longer.
#3 This is a progressive burning powder which makes it different than 777 Pyrodex
and black powder.
#4 Some of the effects noticed are from the pressure being maintained longer not from higher pressure, this includes blowing the cap off open breach guns which is why you are advised not to use Blackhorn in them you could end up with the cap stuck in your eye or forehead.
#5 Because the powder is coated with a sealant retardant which keeps out moisture and partly controls burning speed it is harder to ignite, and a sealed ignition works best.