MAD DOG,
You know a whole lot more than me about hardened steels and heat-treating, but here's some hypothetical grist for your mill.
The fact the fouling from hell is ferromagnetic got me thinking. Consider how it may have formed:
1. smear out a thin layer of iron (abrasion from iron/steel bullet traveling down the bore)
2. dust with fine carbon particles (from unburned powder)
3. heat under high pressure (by shooting another round)
4. quench (the very thin fouling layer "shell" has large surface area contact with the barrel, which acts as an effective heat sink, causing the fouling layer to cool relatively fast)
5. repeat
This sounds like a recipe for high-carbon steel with a heat-treat method that would produce a hardened steel - like building up thin layers of case-hardened steel. No wonder you are wearing out stainless brushes.
You know a whole lot more than me about hardened steels and heat-treating, but here's some hypothetical grist for your mill.
The fact the fouling from hell is ferromagnetic got me thinking. Consider how it may have formed:
1. smear out a thin layer of iron (abrasion from iron/steel bullet traveling down the bore)
2. dust with fine carbon particles (from unburned powder)
3. heat under high pressure (by shooting another round)
4. quench (the very thin fouling layer "shell" has large surface area contact with the barrel, which acts as an effective heat sink, causing the fouling layer to cool relatively fast)
5. repeat
This sounds like a recipe for high-carbon steel with a heat-treat method that would produce a hardened steel - like building up thin layers of case-hardened steel. No wonder you are wearing out stainless brushes.