Give yourself a pat on the back for being smart! The Freedom Arms site lists 14 gr. of Unique as max for 300 gr. cast, and you know darn well that these are the strongest revolvers made for the .454. I use some of their data for shooting through my .454 barrel on my Encore, it works well, and I've experimented cautiously with some heavier weight bullets. Let me know if there's something you're interested, I've got some loads that shoot real nice out of my Encore.
Selmer