Using a fairly light load for .357 with one of the worst powders I have ever used for ESs makes his conclusions meaningless.
I've read some of Mr. Gibson's material and he always does good, extensive work even if we may not always agree with his conclusions. However, the primer project using Unique powder seems to be perfectly valid and he adds a disclaimer in bold letters that none of his results were to be construed as a general rule of thumb.
Yes, other powders and different charges would provide different figures. These projects, even the simple ones, require tedious work and a lot of time, not to mention incurred expenses. To change just one factor (component, charge weight, etc.) makes for an entirely new project and lots more time, work, and expense. No one can be expected to do such work endlessly.
For what Mr. Gibson put into this and considering the necessary parameters to make the report manageable, I think it's a good one.
Today's fixation with ES and SD numbers is hard to imagine. These numbers indicate consistency only, not accuracy. There are many, many other factors that come into play and contribute to accuracy. While it's possible to have a good accurate load that has low SE and SD numbers, it's just as likely that a load with mid-range to even high numbers might shoot just as well. If the numbers are really wild, the load will probably be a poor one, but we don't often get real wild numbers.
ES and SD probably aren't worth considering if your group sizes are consistently small. The exception to this might be at long range.
If you want low ES and SD numbers, try compressed rifle loads using slow-burning power. Numbers are often very small or even the same. The loads may or may not be accurate.
