....It still isn't steel though... in steel the Carbon and Iron form an actual crystal, and there are variations thereof. A mono-steel I would expect would have to be heated above it's critical point to become homogenous, am I wrong?
Another question craigd, and I think you've done some work with steel and iron... why would not the excess Carbon 'burn out' of the iron during the welding process? It does so with steel during forging, and the forger has to limit the time carbon steel is held above a certain temperature to avoid this.
I'd suspect since iron and steel were forge welded together, they easily exceeded the critical temperature of the steel. That may not be really important here. The original smiths may not have had any intention to harden the barrel, and the carbon percentage in the steel, not the inclusions, may not be high enough to harden anyway.
Steve C. had a good comment about loss of material due to the forging process. It may be important to control times and temperatures, but I think most of the material might be lost as scale due to oxygen exposure. Maybe.
