My belief is that each bullet has velocities nodes that work well for it. One needs to discover where these nodes are. This is why one hears of someone shooting a specific bullet caliming insane accuracy at a specific velocity and other finding equaly insane accuracy a few hundred FPS faster or slower. So the guy with the fast velocity says "push it hard" and the guy with the slower velocity says "I like them accurate more than I like them fast."
The truth is, they are all correct. They just found different velocity nodes.
So this is the way I go about finding the node that I want. I pick my the bullet that I believe will help me achieve my goal. I realise many of you are tired of hearing about long range shooting, but that is a very demanding discipline. My goal is to have the bullet arrive at the 1000 yard line at greater that Mach 1.2, because I believe the transoninc disturbance are begins to affect the bullet between Mach 0.95 and 1.20.
So, I pick the bullet that has a BC and a weight that will allow me to have the minimum velocity at 1000. I always discount claimed BC a little it, more depending on the manufacturer. I run the numbers on JBM until I figure out the minimum MV required to achieve my goal.
If you are a hunter and your goal is a PBR of 350yards or some such, you can run the numbers with the bullet that you want to use for its terminal ballistics and come up with a minimum MV.
So let's say we are looking for a minimum MV of 2750FPS, these means we need to look for an accuracy node that is higher than that velocity. In my case, an insanely accurate node with 2600 FPS MV is useless to me. If the PBR you want needs a minimum MV of 2750, 2600 is not going to do it for you either.
I prepare a bunch of cases and the bring a press, bullet seating dies and powder measure (scale) to the range, along with a chronograph. I did my homework at the powder manufacturer website and I know the minimum load needed for the velocity we are looking for. I load cases and shot one at a time over the chrono. In a few rounds, I will have found the load that meets the MV I am looking for.
Here is a strange observation for you, I can actually feel when an accuracy node is reached, the report is minimal, the disturbance in the rifle and the barrel is non-existent. You have to see it to believe it. The more scientific approach is to load 3 cartridges at .5 grain interval and either run them over the chrono for ES and SD or shoot for group. If you can do both at the same time, good for you. You should be able to find the upper and lower limit of the target accuracy node and I find the best accuracy will be in the middle of these limits. You can then play with .1 or .2 increments, but I usually call it good enough.
When I reach that, I then load 5 or 10 cartridges with that load and shoot for a good group. You have to be able to say; "good enough for me."
At that point, you can mess around with bullet seating length if you want.