This is a close as I can get. I estimate that 8.0 grains will give you around 800-825 fps, based on my data with these 45LC's.
51/2" USFA Rodeo
250 LRN (.452") 8.5 grs Unique thrown, R-P cases, CCI300 primers
12-May-02 T = 80°F
Ave Vel = 855
Std Dev = 16
ES = 59.91
High = 885.4
Low = 825.5
Number Shots 12
M625-9 Mountain Gun 4" Barrel
250 LRN (.452") Valiant 8.0 grs Unique lot 6/21/1993 thrown, R-P cases, WLP primers
25-Mar-07 T = 80 °F
Ave Vel = 814
Std Dev = 24
ES = 72.81
High = 847
Low = 774.2
Number Shots 11
accurate
255 LSWC (.452") 8.0 grs Unique thrown, lot 6/21/1993, Starline cases, WLP primers
25-Mar-07 T = 80 °F
Ave Vel = 800
Std Dev = 30
ES = 99.02
High = 847.2
Low = 748.1
Number Shots 11
accurate
250 LRN (.454") Valiant 8.5 grs Unique lot 4.3/06 5471 thrown, R-P cases, WLP primers
25-Mar-07 T = 80 °F
Ave Vel = 891
Std Dev = 17
ES = 61.31
High = 921.1
Low = 859.8
Number Shots 27
accurate
Please leave the bears alone. With all the human encrouchment, they are having a tough time surviving.