Col. Cornelius Gilliam, SASS#5875TG

In the high power rifle world (223, 308, 300 win mag, etc.), the high pressure causes the primer pockets to expand and get loose over time and will loose a primer, locking up the gun. I've never seen it with a low pressure 38 special, but it's possible the cases has been reused so many times the primer pocket could enlarge.

I have bottles of both the Australian and Canadian. I can confirm that in my case, they are different colors and different densities. My older Australian powder looks like your pictures. Loaded to the same charge weight, the newer powder produces a consistently slower velocity.

Yup! Of course, I won't have a gun that doesn't reliably fire all of the main brand primers.