Here’s my results from a ladder test today. The sweet spot appears to be 23.6-24.2. This was out of a sionics upper, 14.5" at 475 yards, 77gr smk hpbt, bipod prone, with pstii 2-10. What grain do you think I should go with. Was thinking 23.9 to cut it through the middle. What say you? 
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I’m sorry, I’m not understanding this at all. What are you trying to show or accomplish?
To build a load the rifle likes. I’m wanting to know if I should just take it at the middle, 23.9gr or work it again. I’m just wanting it to hold moa at 500yds
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Took me a while to understand ladder tests. Once I did, I wondered why I didn’t think of it.
I thought this test was done to test/confirm accuracy of turret adjustments on a scope/optic. Can someone explain what this test does for reloading?
You are looking for nodes to where you have little change between charges. In my opinion, you should either do 23.7 or 24.1. You have two nodes there and that would split it with whatever node you choose. Typically not a platform one would be doing a ladder with but seems accurate enough. Do 10 each and shoot 2 groups of 5 of the 23.7/24.1. One target for each charge weight, mark each group and see.
When I do a ladder, I usually shoot 2-3 per weight to rule out any inconsistencies. You can also use a sharpie and color the bullets to tell apart. You may have to use a Q-tip and alcohol to run through the hole and the color will bleed onto the Q-tip. I just use red, green and blue and one unmarked with max of 4 on each target. If more that 4, just use another target, on same level and plot the shots afterward by drawing horizontal lines and also showing center for each charge weight. It’s almost a hybrid of the two methods.
One would do a Tall Target Scope Test for that to test tracking. There’s basically two test for charge weight, Ladder or Optimum Charge Weight.
I don’t understand the ladder test with a single round per rung. There is too much variability between cartridges to be able to definitely say which powder charge produces the best barrel harmonics.
The way it predicts harmonics is by a group-- one round per load, and two or three loads will group together instead of stringing.
We typically will do 2 or 3 rounds at each charge weight and shoot the test at 500 yards (still not as good as 5-10 would be, but it’s what we do). You can usually paint the bullets with sharpie (red, blue, black, etc) and they will leave some color on the paper so that you can distinguish between charge weights. When possible we also try to shoot the test with a magnetospeed (on a mount that keeps it off of the barrel) to record velocities, but that’s not necessary to get useful data from the test.
The bullets were colored, something I learned from here. I had built three of each load, ran three groups of tests, but the first two didn’t turn out. My paper wasn’t big enough and aiming point wasn’t high enough so I didn’t get all shots on paper.
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I did ocw first, then the narrowed results I came back and did ladder with. But the ocw was awhile ago and I forget the results.
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Here’s the ocw test. I found it in another post of mine. 
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