By setting my seating depth very near to jam, I have a "worst case" situation for pressure. This is only to establish my maximum charge. With some bullet shapes, I will also use that seating depth as a starting point for accuracy workup. For others, I will do another series farther out of the rifling, but usually longer than touch. I generally load longer than touching, so that the rifling marks the bullet to some degree, and although this produces more pressure than the same powder charge would with the bullet jumping, I avoid any safety issues by doing my pressure test with the bullet seated to produce the highest pressure that it will, from seating position. That way, I will always be under that pressure limit.
As to what I am looking for on the test target, I look for a range of powder charges that do not show much bullet impact change.
If you have a rifle that is well made, and you are shooting over flags, on an easy wind day, from a good rest, if you shoot two shots very quickly, while the condition holds, you will have a good starting look at the accuracy potential of a particular load. That is how I do my post pressure test load work up. Once I have something that looks good for two shots, I shoot groups of more shots, up to five. For those that think two shots are not enough, consider this. If two shots form a group that is too large, will more shots make it smaller?
I cannot overemphasize the advantages of loading at the range. Those of you that are still loading at home and driving to the range are giving up a huge advantage, wearing out your barrels more than is necessary, and probably never arriving at the peak tune that you might, unless your shooting temperature conditions are very stable, throughout the day and year. For the vast majority of us, a load that is in perfect tune first thing in the morning, will not be when it heats up in the afternoon, and a load that was worked up in the early spring, will not be in the heat of summer. By loading at the range, adjustments can be made for that days conditions, and as the day''s conditions change, so that you will have better average accuracy, and can concentrate on the more difficult part of the problem, dealing with the wind, which of course requires some way to see what it is doing, between you and the target.
While I am at it, let me pass on a little piece of advice to those of you that want to shoot smaller groups. Don't study your group until it is finished. After a suitable follow through (extremely important), rapidly reload the rifle, and aim, glance at your wind flags, and if they have not changed, shoot your next shot, repeating as many times as the length of the wind condition will allow, until you have finished your group. When the wind shifts, put on the brakes, and wait for the condition to return, You cannot wish the shot into the group. It will go with the wind.
Back before I had any way to look at what the wind was doing, I felt no sense of urgency when shooting a group. I would fire a shot, and either admire my work for a while, before reloading the rifle, or sit and wonder what had gone wrong, and then reload and aim. When I put out my first flags, sticks with surveyor's ribbon, I soon figured out that I needed to make a change, and my groups improved.
