With rifles in the .243 family (including 6mm) I usually start with a mid range load (using data from a reliable reloading manual) with bullets seated about .020 off the lands. I load up five round sets, increasing the load sets by no more than .3 grains. I try not to get closer to max. load than 10% below the max. on the chart and I watch closely for ANY signs of high pressures. I stop at any of those signs, pull the bullets, and remain under the potentially dangerous load weights.
I shoot one five round set at each of a number of four square inch targets, at 100 yards, and determine where the node for the series of targets appears to be the most consistent. Once I've identified the best load in this test, I reload another quantity of this load and arrange three round sets with varying seating depths, lengthening the OAL by a factor of 15% for two of those sets and decreasing the OAL by the same factor for three sets. So I've got five at .023, .026, and .029; and three sets at .017, .014, .011, and .007 for a total of thirty five rounds. I repeat the square target sample run, again watching for pressure signs, and find the most promising series before applying that load to a 300 yard target. Depending on results, I may run the best three 100 yards results in a ladder test at 300 yards but I'm usually satisfied with the results of the initial test series to obtain good varmint shooting results.
My current load performs best with a moderate powder charge behind 107 grain bullets with the bullet seated .012 off the lands. That puts the group consistently under .75 inches at 100 yards. No, it's not going to win any bench rest matches. But it takes out varmints very well.
I have a great woman, fantastic kids, a warm place to sleep and an accurate rifle. Life is good ..............
Hunter Safety Instructor - Rifle/Pistol Marksmanship Instructor
American riflemans triad - God, guts and guns. It built America and it'll preserve America. Abandon one and you lose them all.