I did use the OCW method, in conjunction with the chronograph, for a while and found that the lowest SD (Standard Deviation) did not always correspond with the most accurate load. However the most accurate load was usually just below or above the one with the lowest SD. For long range shooting the lowest SD load may be preferable as it will have less vertical at the longer ranges. Here are a couple examples of an OCW load workup.
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The above targets show the most accurate load at 20.6 grains H 4198 with the 32 V-Max and 20.3 grains as having the lowest SD. The 20.3 grain load shot to the same POI as my 32 Sierra BK load with H 322 and proved to shoot consistent sub 1/2 MOA in all rifles.
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I do prefer to use what I call a "Pressure Ladder" using only one shot per powder increment which is 0.1 grain in small cartridges like the 20 EXTREME, 0.3 grains in intermediate size and 0.5 grains in large cartridges. I like to use the chronograph and watch for pressure spikes, as indicated by increase in incremental velocity. These pressure spikes are usually followed by a drop in incremental velocity and result in bullets clumping together. These nodes can produce very stable loads over more than one increment increase in powder. the first node is usually found as the new brass first starts to expand beyond its elasticity and the second is when pressures are reaching max and near fire forming to the chamber. There is usually one found when fully fireformed brass is used but pressures are likely well beyond Saami .
Here is a ladder I did with the 55 Berger using Varget and Remington Brass.
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Shots 4, 5 & 6 clumped together in a 0.060" group so I did 5 shot groups over the Chronograph.
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Varget 22.2 300 meters:
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Varget 22.2 500 Meters:
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