You might poke around over at
http://www.littlegun.be/arme%20belge...belge%20gb.htm
which is a Belgian site about Belgian and other European guns.
Damascus, wire twist, stub twist, laminated steel, etc., might have different detailed meanings to the real collector but the manner of construction is the same; hammer welded strips of iron and steel formed around a mandrel, then reamed and ground into final shape for a gun barrel.