I get very good results with 14 grains of unique or 21 grains of 2400 over any cast bullet between 300 and 400, but the velocities are no where near 1350, more like 1150-1200 per my chrony. Both powders are incredibly accurate, I shoot 2-4 inch groups off the bench with my tang sighted rolling block or my sharps repro. I have aperature sights up front too, really tightens up the groups. Do not fall into the trap of using large pistol primers because you are using pistol powders! Large pistol primers are shorter than rifle primers and you might find yourself in misfire city! You can shoot a hundred rounds of the above loads and not go home hurting, but load up some 300 gas checked bullets over 52-55 grains of RL-7 as I use for hunting out of my Ruger #1 and feel the push!
regards,
Graycg