As an old Pittsburgh metallurgist, I can put that old tale to rest. Most people don't know this, but all steel is composed of crystals. "Decarbonized" was a term used to distinguish the newer methods of iron and steel making from the wrought iron days. Given the age of the gun, it's likely the steel came from a Bessemer converter that blew air through the molten pig iron to remove the excess carbon. So, simple carbon steel, weaker than modern alloy, but steel nonetheless.
I was hoping to hear more about Remington shotguns of this era
