Soak it in kerosine. Repeat as required. No need to reinvent the wheel.
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Soak it in kerosine. Repeat as required. No need to reinvent the wheel.
Dont use Sweets if it's a stainless barrel tho.
Man, that's an ancient technique. Was relevant for .303s that had corrosive potassium chlorate primers which left potassium chloride (salt) in the barrel. Flushing with boiling water helped prior to the main cleaning.
Getting back to the orig query, copper fouling that stubborn needs mechanical agitation with say KG12 and left to soak for several hours. If after say five cycles of this the borescope is still showing fouling, it's time to get out Autosol or JBs. Autosol for sure is NOT significantly abrasive on the rifling. Actually, in this case, it might help make the bore less prone to copper buildup.