Wrong. High carbon steel has been around for the past two hundred years, or more. Maybe it was used in the 16th through 18th century when muzzle loaders were being hand bored and hand cut. Since the invention of water powered lathes and grinders in the earliest stages of The Industrial Revolution, (1750 - 1820, or so) high carbon steel has been used in firearms all over the world. It makes more sense. Low carbon steel is harder to work than high carbon steel, whether is is turned (built up edge on the cutting tool), more difficult to grind (loading of the stone or grinding wheel) and too gummy for efficient drilling. All gun makers have been using high carbon steels for the past 200 years - Spain, Turkey, Pakistan included. If there is a hardness/quality issue for a gun part, it usually is in heat treating, quenching, annealing and so on.
