I have shot a lot over the chronograph with a bunch of different muzzleloaders. I have discovered a thing or two. First most published data is "very optimistic", especially T/C. Secondly, there are so many variables with loading, for example, ball size, patch thickness, cap manufacturer, pressure with which projectile is seated and probably a bunch more, that what is true for one gun may not be true for another, even one of the same model. The only way you will ever actually know is to use your chronograph, with the actual load and components you will be shooting with.
Just for info, my .54 Hawken with 28" barrel gives these results with PRB's:
Pyrodex RS 60 Grains. 1150 fps
75 gr. 1400 fps
90 gr. 1590 fps
Pyrodex P. 60 gr. 1460 fps
75 gr. 1540 fps
90 gr. 1670 fps
Goex fffg. 60 gr. 1370 fps
75 gr. 1500 fps
90 gr. 1630 fps
Hodgdon 777 60 gr. 1530fps
75 gr. 1700fps
90 gr. 1920 fps
Just for info, my .54 Hawken with 28" barrel gives these results with PRB's:
Pyrodex RS 60 Grains. 1150 fps
75 gr. 1400 fps
90 gr. 1590 fps
Pyrodex P. 60 gr. 1460 fps
75 gr. 1540 fps
90 gr. 1670 fps
Goex fffg. 60 gr. 1370 fps
75 gr. 1500 fps
90 gr. 1630 fps
Hodgdon 777 60 gr. 1530fps
75 gr. 1700fps
90 gr. 1920 fps