Well, since everyone else is throwing thier hat in the ring, I guess I will too. I think of it this way...there are two things you are dealing with.
1) You are dealing with powder burn rate and finding the optimal presure to burn the powder cleanly and efficiently as possible without being near the critcal max pressure.
2) You are dealing with barrel timing. Every barrel has a reaction to recoil causing it to whip, just like a bull whip or giving one end of a garden hose a quick shake.
The trick is to get the bullet to exit the barrel at the point where it is changing direction at one of the extreme ends of it's travel. This is the most forgiving spot for the bullet to exit because the barrel has to slow down, reverse direction, and then accelerate in the opposite direction.
This is why you can very often get loads that group very well in spite of a larger than desirable extreme spread in FPS. Conversely, you might have a very good ES and SD and the group might still look like hell. If you can get the powder to burn efficiently and consistently and cleanly while getting the bullet to exit at this point, then so much the better.
So, how do we determine our optimal powder burn rate? First, by finding max charge and backing off from that. But we do it in a very specific way. We figure out the maximum length we can tolerate for our over all length. This might be determined by a short throat, by magazine length, by neck length, whatever. Every rifle is different in this respect. You gotta figure that one out for yourself.
Loading at this length, you load 2 rounds of each charge, (0.5 grain increments for charge weights above 40 grains and 0.3 grain increments for smaller cases) until you find your max powder charge as determined by chronograph readings, and other traditional pressure signs. (flat primers, stiff bolt lift etc.). Once this upper limit is found, you back off the charge by 2%. This keeps you in the most efficient part of the pressure curve yet gives you enough head room for hotter temperatures.
Now we have found the optimal range of powder charge. We now work on barrel timing. The most efficient way to alter barrel timing is to change seating depth. Changing the powder charge in small increments will change the barrel timing also, but it changes the pressure much more. Changing seating depth, alters the barrel timing drastically, while having a much less effect on peak pressure.
Start seating the bullets deeper into the case in .005" increments until you find a depth that looks promising (meaning groups come together and vertical dispertion is minimized). You shouldn't have to go more than a total of .050" before a good group shows up. Once this load is found, you can fine tune seating depth +/- .002" either side just to see what it does.
Take the best of these last loads and you are done. If an obvious load doesn't present itself during this process, then it probably is not a viable combination.
This is the way I have done it for several years now, try it if you wish.
