RE: Bullet or Powder?
If it was a 7400, there is a whole set of circumstances you have to deal with. Or even a bar. You are limited to what cycles reliably. I find in my 7400 that 4350 cycles flawlessly but 4064 and varget does not. The wierd thing is most people will tell you to pick the faster of the powders for a semi. But in my case it doesn't. So therefore, I would change bullets. For my 7400, BT's suck, but gamekings get 1.5MOA.
For a bolt however, I don't worry much about the brand or number so much as burning rate. This is what affects harmonics the most I have found.
For instance, for my 300RUM, I knew the bullet I wanted to work. That was either a Partition or a Accubond in 180gr. I found H1000 to the be most dynamic but only got 3150fps. I picked a faster powder like 7828 and got the MOA groups I wanted and got over 3300fps. I was happy.
So to answer your question, it really just depends on what you want and expect. For a 300RUM, I wanted a moose load, and I expected it to be over 3200fps. For my 308, I want accuracy, but desire 150gr bullet over 2700fps so I am flexable. I have about 24lbs of powder so its nice to have a variety on hand. Both bullet and burn rate can have a significant affect on accuracy.