JPK

You are correct that barrels are not hardened subsiquent to manufacture, however the steel from which they are made is machined in its hardened and tempered state.

CrMo at 30 ish Rc is reasonably machineable, thus it does not need to be annealed prior to machineing. So it combines the properties of hardness and toughness that make it ideal for firearms and ease of production.

Your guys will work these materials routinely in high pressure pipeline systems as it is an industry standard in the oil pipe and fittings field. (there are also some more exotics now in the CrMo range with specific propities but they are not so common im firearms). I will be most please to hear what they have to say as nobody can ever have enough knowledge.
I am about to send a 470NE shoe lump set to a firm that specialises in lazer brazing as they promise that they can use a high melt spelter without changing the core toughness/hardness of the 4140 from which it is made, thus giving me more joint strength without recourse to vaccum brazing. They are going to perform hardness tests after assembly. Do I have the answer to that one ? Well what I know of lazers I learnt from William Shatner

, but I do wait with anticipation.

Please do not think that anything written here is intended as a critic of you or anyone else, it is rather that unless these things are discussed fully, there is always a posibility of somebody just believing that they can buy a TIG set on e-bay and modify their own guns, based on what they have seen written here.

Regards