There are a lot of new loaders on the forum and I think this thread gives them more exposure to different types of powder, since they're unlikely to have had a chance to see more than a couple of powders.This thread is interesting, but I have to confess, besides seeing that different powders look different, I don't understand the point of this thread...
The chemical and physical composition of each powder is unique. They are developed as trade secrets. Single base, double base, a huge variety of burn rates and gas generation characteristics. None of this can be determined visually.
Reloading manuals exist because you have to determine safe loads (that don't generate overpressure) experimentally. This is done with instrumented chambers using specific compoinents and known powders. The experiements are measured, and the information on safe minimum and maximum loads of a specific powder / case / bullet / primer / chamber / barrel combination are published.
Going below the minimum or above the maximum generates dangerous overpressure.
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So... you find an unknown powder. Do you compare it to the pictures in this thread, and load according to the tables for a powder that it looks like? I don't think so! That is unless you want to perform your own experiments...
if you find an unknown powder, throw it away....
But I totally agree that you can't tell anything about a powder by its looks and the proper load data should always come from reliable sources, like loading manuals or powder makers.