Well their is certainly going to be a difference at some point when you switch from a low explosive to a progressive burning powder.
In fact there is liable to be several points at which there is a feel able difference.
A low explosive has a set rate burn so it actually works best with a light load, Blackhorn is going to be almost the opposite because progressive burn powder burns more efficiently with a heavy load and more pressure. That's why you will find 777 working very well with loads at 110 and lighter bullets it will actually be a bit faster. Blackhorn will be faster with 120 grain loads and heavy bullets. A low explosive has a very sharp pressure peak and Blackhorn has a lower longer pressure peak. 777 at 120 grains and Blackhorn at 135 grains will have about the same maximum pressure peak but Blackhorn pressure peak will be more than twice as long. If it were not for the crud-ring I would use 777 for a lot of loads and bullets but it just is not practical to use it in high humidity areas, but the people who live in a high altitude area have great luck with it.