I thought this was a pretty interesting guide. I'm not the chemist that a lot of my reloading friends are but pretty cool nonetheless. That's Vihtavuori Powder on the left-hand side versus the slower burning Hodgdon Powder on the right. It's interesting to see the real-time burn rates. Obviously, inside an ammo cartridge you don't get to see the combustion that you can see in this example. I'm curious if the pressure inside a cartridge plays a role in how it burns though. I would assume with limited oxygen that would play a role in how the fire eats fuel.
Widener's has some more neat images in their smokeless powder guide. If you're curious about reloading (and with the election ammo rush in full swing, who isn't?) it's worth 10 minutes to check out.