OK, I don't have a Springfield but I've got 3 Parker Hale Enfields (3 band, 2 band & musketoon) that I shoot. Regarding the minie, it's a Parker Hale minie mould that was made by RCBS for Parker Hale in the '70s. I believe it's .577 and most Springfields like the .578. Never weighed my minies but I used SPG lube and 65 grains of FF, the historical load for the Enfield (and most Civil War guns).
The guys at the
http://www.n-ssa.org are the die hard enthusiasts when it comes to bullets, accuracy in firearms (both appearance & groupings). You may want to drop in and say hello.
Here's some info I got out of the Gun Digest Black Powder Loading Manual by Sam Fadala (1982 ed.):
Zouave Rifle (58 cal) w/1:48" twist. Projectile is .577", 530 gr., Lyman Minie mould 577611, 32 1/2" bbl:
powder mv me vel @ 100 yds energy @ 100 yds
50 FF gr 850 fps 850 ft pds 782 fps 720
60 FF gr 971 fps 1110 ft pds 879 fps 910
70 FF gr 1035 fps 1261 fps 932 fps 1023
80 FF gr 1095 fps 1411 fps 953 fps 1069
Mississippi Rifle (58 cal) w/1:48" twist. Same projectile & mould as above. 33" bbl:
50 FF gr 853 fps 857 ft pds 785 fps 725
60 FF gr 975 fps 1119 ft pds 882 fps 916
70 FF gr 1034 fps 1259 ft pds 931 fps 1021
80 FF gr 1102 fps 1430 ft pds 959 fps 1083
from Gun Digest BlackPowder Loading Manual (3rd ed):
Navy Arms 3 band Enfield (58 cal), 39" bbl, 1:48 twist. Projectile 505 gr. Buffalo Bullet
70 FF gr 1004 fps 1131 fpe 870 fps 849
100 FF gr 1195 fps 1602 fpe 1028 fps 1185
Sorry but the Lyman book has a lot of loads, but it depends on the bullet you're using. Bear in mind that the most powerful load isn't necessarily the most accurate load.