Pyrodex P is a good powder. When I was shooting lots of BP revolvers I used to burn a lot of that. Then got away from revolvers and what Pyrodex P I had left, ran it though my Renegade, standard barrel. I was very pleased with the accuracy but never did test the velocity with a chronograph.

White Rifles used to recommend Pyrodex P I believe. I shot it in my Whites and still do. Although I found a load with 777 2f that works even better. Those are impressive looking rifles and numbers you have there.