Chuck;
Be vey careful with it, don't "Peel" it.
Yes I am fully aware there are bbls which have been hard chromed, have one myself.
As you know though a 4140 bbl would be harder than a 1040 bbl. The 4140 has a chrome component in its alloy. I don't know if this alloying is what Quack WtIS (Wonko the Insane) is referring to as "Chrome Hardened" or what. I put over 35 years in machine shops mostly with inhouse heat-treating & like you I never heard the term Chrome Hardened.
This chrome alloy steel while harder than a plain carbon steel would of course still not have the high surface hardness of a hard Chromed (Lined) bore.
