there are different levels of a burn,,
what I mean is when it goes into the skin is does it while its hot and is why it stays for long periods of time and wont just wash off,,,
I've shot 10's of thousands of pistol rounds and I know you're full of shit.
The semi burned powder comes out of the barrel not the ejection port.
When they check for residue it's the smoke that leaves traces not the unburnt hot powder.