Copper "washed?

I have visited several ammo factories and have always seem bimetal cases drawn from bimetal strips. Is copper washing an actual process or just a term used in North America?

Copper plated (bimetal): The copper is rolled onto the steel strips the coins the cases get drawn from are stamped from.

Copper washed: The whole case after it got finished is galvanized in a bath of liquid with electricity and a piece of copper on one pole of the electrodes.

But in copper washing is the strip plated, then drawn, or are the cases plated after they are finished? I have never seen the plating process in use in the plants I have visited, despite the ammo from those plants being referred to as 'copper washed"

I think Alex means that the whole steel cartridge (after it is fully formed) is galvanized with copper molecules slowly leaving one electrode and layering the other, which is the steel cartridge itself. I’d love to see this operation.

Yes, I understand. Has anyone ever seen a true “copper washed” case? I have seen many cases said to be “copper washed” that are in fact bimetal. Does anyone know of a factory that electroplates cases?

CanAM–I believe the cases from North Korea are Copper Washed or Copper Electroplated. At least they have a coppered extracter groove, not a black or gray lacquered one as is most commonly seen.

Very interesting. I will search out some pics. That actually makes sense as NK may not have the necessary rolling mills to produce bimetal, so they electroplate instead.

My understanding is that usage of steel is because of availability and cheapness. Then unprotected steel started to rust. Copper “covering” was a way to prevent rust. Did anyone attemp to submerge inverted finished loaded ammo in hot wax or hot Cosmoline because, if this method of preventing rust worked, it would be much cheaper than electrolysis? And wax would melt in the machine gun and not jam it like lacquer did.

Some machineguns/ammo combinations required oiled, greased or waxed cartridges to function (Italy and Japan come to mind). WWII Germany used a dry wax coating on some lacquered steel cased MG ammunition. Generally speaking though it is a bad idea. Oiled cartridges reduce the friction between the case and chamber, causing excessive rearward thrust, which can damage the weapon. Also, oily or greasy ammunition can attract dust and other contaminates which will adversely affect the operation of the weapon.

As for the term copper “washing”, I think it is misleading. The process described as washing is actually “plating”. The process described as “plating” is not actually electroplating since the copper and steel are mechanically joined through the rolling process.


German World War One steel cartridge cases were drawn from copperclad sheets, and after the extractor cannelure was cut unplated steel was exposed. In some situations this unfinished steel was left as is, but in others the cases had copper electroplated over the base area to cover this exposed area. With a little effort both types of cases can be seen. JG