"Not with any fire extinguisher in existence."
Maybe that's why I said this...
"Takes a ferocious amount of water to do it, though, and involves not only cooling the powder but also using water to force separation between the granules before they can ignite each other."
Let's also consider just how much powder we're talking about.
Now I might be a little different from most handloaders in that I keep 100,000 pounds of powder sitting around in open containers and use drip torches to illuminate my stash, so I might well be screwed.
But most people don't keep all that much powder on hand.
So, while a fire extinguisher might well not put out that 1 pound can of Bullseye that's sitting there sputtering and glowing like a nookulur gopher, that fire extinguisher may well keep other stuff around the powder from catching fire.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.