So glad you replied. I don't have a background in metalwork of any kind save a little minor gunsmithing, so I have to read a lot. Most books about the subject confuse more than they help. If one wants to know a useful answer to the question "is a stainless steel firearm tougher than a carbon steel one?" he'll get a lot of "it depends" answers.
One quick observation though. When I mentioned iron's use in firearms, I wasn't speaking of cast iron. I know that cast iron is much too brittle. But I do know that steel was very hard to come by in any appreciable quantity before the mid 19th century--certainly not in enough quantity for the majority of a firearm to be made of it. Wrought iron was used extensively. It will caseharden, which was really the only way to harden it. By packing it in charcoal, bone, leather, etc. and heating it, enough carbon was diffused into the surface to allow the skin to be hardened. I know that springs and frizzens and such had to be made of steel, but the old rifle barrels were usually made by forge welding iron strips around a mandrel. As to revolvers....
Well I guess I really don't know for sure. I've "googled" every combination I could think of to no avail. But I am usually pretty good at remembering little details I've read before, and I remember reading about steel's widespread usage's not occuring until after the civil war. I have an English book on revolvers from 1818-1865 that deals mostly with Dean, Adams, Webley, etc. It mentioned that Adams used wrought iron for everything but the springs in preference to steel. But I just read that Colt used cast "blister steel" to forge its barrels from. This process produced steel that was often less than homogenous in its distribution of carbon, but it WAS considered steel.
So I guess I have to stand corrected on my earlier assertion that all the old revolvers were made of iron. And I haven't been able to find a thing of how Remingtons were made.