How do these compare? Do they shoot the same velocity with the same volume charge?

777 is suppose to be hotter with the same volume charge. It does not stink but still smokes. If you switch from Pyrodex RS you will have to re-sight. The fun of shooting Black-powder rifles is the stink and smoke and having to be sure you have made a good shot placement because you can't see your hit until the smoke clears. I just love the smell of black-powder in the morning.