I don’t know who told you this, but it’s 100% false. Doesn’t matter what rifling process is used, it’s the same steel. Barrel companies don’t make steel. They by 416 SS (mostly), and/or 4140 Alloy steel. The steel is shipped to the barrel maker as Round Billets. Typically, the longer the Billets, the cheaper the cost. The steel doesn’t come harder or softer. It’s all supplied as annealed, which is steel in its softest form. The billets get cut & are heat treated to the makers specifications. When talking about “hardness” understand that rifle parts are all pretty soft as steel parts go. As a custom Knifemaker, I heat treat & temper my steel blades in the high 50’s to low 60’s HRC. In the world of firearms, the steel is heat treated & tempered in the 30’s… maybe 40 on the HRC scale. This is butter soft to a knife maker! But is necessary as 60hrc, even 50’s, would be far to brittle against the shock of firearm fire. (By the way… steel being hard or soft has no bearing on it’s strength or toughness.) After machining and rifling, the barrels are once again stress relieved (tempered), because no matter how the rifling is done; Cut, Button, CHF… stress is induced into the steel. A tempering relieves this stress. Of course each company has their own specs, places of doing what steps(besides final stress relieving at the end), and I don’t know them.. but I know they MUST follow the same guidelines as everyone else for using steel to make parts. It must be heat treated & tempered after annealing. And as far as buying the steel, they buy from the same places. I can tell you every major US steel supplier (maker) in the country if you like. And I can tell you which ones the top barrel makers likely use because I know which are best. That is, most consistent.