Re: Creighton Audette method for developing loads?
The only thing I can add to what BH said is that the horizontal extreme spread will also be a good indicator when you're not in the zone, you just have to try it to see I guess. Every gun is an individual and you can expect to see any where from .5" to 3.5" spreads between shots, not all of it is from increase in MV, or change in bbl whip. Recoil effects this big and a few other minor things too. Be consistant with bench technique and the results will be most interesting and helpfull. A lot of the vertical spread depends on how well the rifle will shoot the load throughout the range, the more it likes the combo, the tighter the vertical, the worse it likes it, the wider the spread... in most cases.
I can't find a single pic of a target I've done this with or I'd post them, I know I had some at one point. I'll be sure and get some of the next ones tho.
Everything BH said about plotting each shot correctly on a target, or drawing of one at the bench is critical. if you can't associate each POI with the charge weight it had in it, it's perfectly meaningless.
At some point you may have to even go down range after each shot and mark each shot, don't wast your time by keeping on shooting if you aren't sure.
I fire three or four foulers at the starting load before I ever start the test too. The bbl is let cool so it remains about the same temp for each shot.
Dan Newberry has a modified way of doing it also, but Dan tends to only shoot near the top end range and a pretty narrow one I might add. As my dad does, he looks for where the POI shifts in the group are. Dan rarely goes to 300 yards with his tests tho, and I believe the ILDM (incremental load development method) as Audette used it is more usefull, in that all the loads increments are grouped together on the same target and there is nothing to figure out to measure the shift etc. 300 yards is minimum for good data IMHO.