RE: 454 casull loads
My Lyman manuall has that bullet in it, and it's the one I started with also So as far as an accurate load I haven't found what my gune likes yet. In the Lyman book it uses small rifle magnum primers ( cci 450) and lists only 3 powders 2400, AA #9 and IMR 4227 ... with the 4227 being the probable most accurate. I had the 2400 and #9 on hand so that's where I started.
2400 22.0 - 26.5 MAX
AA#9 24.5 - 29.0 MAX
IMR 4227 26.0 - 30.5 MAX and in their book listed as most accurate
Good luck
Note one thing the Hornady manual only lists the xtp mag bullets for the casull