CLEANING A SHOTGUN
Rifle barrel cleaning solvents – the type which smell of nitro benzene – are designed to remove metallic fouling from the rifling.
This is usually gilding metal, which is a high-copper brass.
They do this by attacking the copper, and reducing it to a green salt.
They will also safely remove plastic and lead from shotgun barrels, although you don’t usually need anything quite as powerful for this task.
At risk of giving a free plug, I usually use Napier shotgun barrel cleaners, although there are plenty of other good ones out there.
One sort of cleaner I do avoid is the type based on soluble oil, which is meant to be used dissolved in water.
To me, water means a risk of rust unless the stuff is used very carefully.
If you do have to resort to rifle barrel cleaners, remember that your bronze brush has a high copper content, and the solvent will attack the brush unless it is washed out immediately after use.
And yes, I’ve done it – reduced a 12-bore brush to a 20-bore in a matter of days!