Mike Rowe, I agree with 3DogMike. Your input is well appreciated. Please continue providing your insight.

3DogMike, From what I have read and been told by older shooters, one should reduce the black powder charge by the energy level of the added nitro powder. That is, if you use say 2 gr of SR-4759, you should reduce the black powder charge by 6 gr to keep the pressure the same.

Chris, Best success with your loading. BTW, I have used .511" hardcast bullets (both 350 & 440 gr) pushed by 4.75 dr of 2F in my 500 BPE. I use a dip measurer with loads measured in drams with 1/4 drams increments. I once weighed BP but found no difference between weighed and dipped charges.