V.H:
I just received a Loading Data Sheet from Freedom Arms for the .454 Casull and they have some reduced loads for 300 grain jacketed bullets. I would think these loads are interchangeable with HARD, Cast bullets.
Let me know what velocity you would like to shoot the 300 grain Lead Bullets at and I will send the data. The loads listed range in starting velocities of 804-1026 fps for Bulleseye, 820-1076 fps for HP-38, 824-1062 fps for W-231, 1049-1275 fps for Unique, 1084-1450 fps for HS-6, 1100-1440 fps for W-540, 1107-1494 fps for W-571, 1111-1501 fps for HS-7, 1177-1625 fps for A.A. No. 9, 1240-1534 fps for Bluedot, 1290-1491 fps for N-120, 1346-1622 fps for A.A.-1680 ............................................. and many others, each with a higher starting point of fps. - J.Solo