Thread: Red colour inside 44-40 case??

Sorry to be a "Pedantic peter " but it's a common misconception that black powder residue is acidic, it's actually slightly caustic due to potassium carbonate and sulphide in the residue. Iron and steel don't corrode in alkaline conditions. Corrosion however occasionally occurs when the sulphide gets oxidised by air to sulphite.
Not that there's much of it but smokeless powder residue is acidic.