Thank you Mr Thomas for taking the time to write this up, made me think, and reconsider what i am going to do here.
Let me try to repeat back, and please tell me if i got this wrong:
Assume it is a new rifle in a popular caliber like 6.5 CM, so we know what 2 or 3 powders shoot well in that caliber, that are fairly well temperature stabilized, and what projectiles gave good results for others (good enough BC, very good BC consistency). Assume it is a well built rifle (bedding, quality of the barrel, crown, chamber job, scope is properly mounted). Assume premium brass that is “fully prepped”(means different things to different people, but let’s ignore that for now).
Proposed load development steps:
1) Pick the most promising powder and bullet. Set the tuner at zero. Pick a seating dept like a 20 thou jump that is known to work for this particular bullet. [A jammed bullet will require a new load development experiment, as the powder charge will have to be much lower.] Start with a clean barrel and fire 10 - 15 fouling rounds (use cheap commercial ammo), wait for SD to stabilize to +- 15 fps or better for the last 5 shots.
2) Run a quick pressure test to see where the chosen combo of brass, bullet and powder maxes out. Maybe 5 rounds total. Assume max safe pressure is reached 0.5 grains lower than the point where a full ejector mark shows up, to allow for ambient changes.
3) Run a ladder test in increments of 0.3 grain (?) for the top 2 grains of powder range before pressure maxes out, firing 3 shots at each powder charge, and record and plot SD. [Combine data from item 2 to reduce total rounds fired.] Find the powder charge where SD is minimized. If the picture is not clear, fire more rounds in the area that looks promising. Hopefully one or two adjacent groups produced an SD below 5 fps.
4) Load 50 rounds (?) at the powder charge that gave the best SD. Test at a range where you can still see your bullet holes in a Shoot’n’See target. Probably 300 yards, or 400 if done in winter with no mirage. Or invest in a target cam or an electronic target and test at long range, say 800. Fire two rounds, if the 2 shot “group” is worse than 0.5 MOA, adjust the tuner two hash marks, and try again. If below 0.5 MOA, fire a 5 shot group. Find 2-3 adjacent groups where POI did not move much (less than 0.1 MOA?) and group size was acceptable (better than 0.4) but there is still room for improvement.]
5) Now move the tuner in smaller increments, like one or half a hash mark, shoot 5 round groups and find the best compromise from the pespective of lowest POI movement compared to adjacent groups (positive compensation is working for you at your chosen distance) and minimal group size (hopefully below 0.35 MOA).
6) Now optimize seating depth as well, in increments of 5 thou, adjusting powder charge slightly to keep speed the same? Probably optional if you managed to get by so far with a longer jump? Aim for 0.3 MOA and stop as soon as that is achieved to save on components and barrel life. [Repeat at different ranges and see if half or one additional/less hash mark will compensate for the difference in distance??]
7) Know the powder sensitivity to ambient temperature (fps per degree F), and and adjust your load a small amount as the seasons change to keep speed the same.
8) Slowly adjust seating depth maybe every 100 rounds as your lands move forward, so “chase the lands”?
BTW: I have the equipment to reload at the bench (Wilson dies, arbor press, battery operated scale) so i can interactively adjust seating dept, powder charge and neck tension. [But there are too many variables!]
Looks to me like this could consume 150 plus rounds.... Any shortcuts that folks have used with success? I am wondering about the potential benefit of “Design of Experiments” here to minimize rounds fired..
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