Like you, I have to make a decision on the bullet and it's purpose/result...
I have three basic powders that I use and will choose one depending on bullet weight and barrel length.. I want the burn rate to match the barrel length as much as possible and still give me a nominal amount of velocity...
I generally have a factory round in the caliber with a similar bullet weight and design and will set my initial seating die to that length...
I'll make ten rounds of each powder charge, in .1gr, or .2gr increments, starting a full grain below published max and seat the bullets to the factory length to start...then it's to the range for testing...If out of the batch I get a reasonably good group of five, I'll use the other five for verification...The rest go back to the bench for additional tweaking with the same powder charge as the one that gave me the better group, but with seating differences.
If my magazine will hold and overall length of 2.26" and the initial factory round was 2.25", I'll work in .002" increments on either side of the better group..If they still are not providing what is acceptable to me, I'll change primers and go again...Eventually, I will find the 'perfect' load for a specific rifle...
