Saeco #020 540 gr fpgc sized @.459 with 50 gr 4831 in my 45/70 has put 25 shots in 2 1/2 inches @ 200 yards. just bump up the powder charge some use Accurate powder data for reference.
I tried all of the usual powders and this gave me the best accuracy, also bullets much over 450 gr may have to be shot @ 200 yards to stablize correctly to obtain the best accuracy