From the Hornady#7 Page 660 using Trapdoor Data for their 300 gr. HP
from a Springfield Model 1873
WW Case, Federal 210 primers.
Reloader#7 powder
1300 fps 1400fps 1500 fps 1600fps
31.6gr 33.9 gr 36.3gr 38.6gr
Note. Max powder charge not to exceed 25,000 cup was 45.7 gr for 1900fps
" The rifle used has a 29 1/2" barrel.
Going into the next level to 40,000 c.u.p, the max is 52.3gr for 2000 fps from a Marlin Model 1895