Winchester Auto Comp and other Powders???

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Is it just the light in the photos or is AA7 slightly greenish in color compared to the gray/black of the AA9?

Mostly lighting.  The camera never shows it how my eyes see it.  Depends on the light and the angle I view the powder from the light.  In general though, from a distance of around 1.5', it simply looks dark gray to me.  If I get up close (a few inches from the powder) I can begin to discern different color shades a bit, and even a little more so when looking at is through a magnifying lens.  In general though it is pretty much just dark gray.

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People have mentioned that the powders have undergone some changes in recent times, they mentioned more of a flattened ball structure as compared to the sherical ball of the older powder structure.

No doubt about the shape changes over time.  I wonder if the actual recipe was ever adjusted, or if it was limited to shape changing alone.

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shape impacts burn rate to some degree.  Accurate Arms buys the powders from different suppliers and then packages it.  They specify a burn rate an general characteristics like ball, stick, etc.  So, when they switch mfg, which happens every few years, small changes in formulation and specific characteristics, like ball size/shape, change too.