Help out the SAF by shopping on wholesale golf clubsAmazon through this link. Context and explanation found here. Our company manufactures cutting tool bodies made of 4340 and H 13 steels.
These steels are then nitrided or not based on customer preference. We have found the nitrided tools to stand up much better to abrasive wear than the non nitrided tools under the same conditions. Nitriding makes the surface of the steel extremely golf wholesalehard (around 65 68 Rockwell C scale, though that scale isn used for surface hardening). It also adds compressive stress to the steel, while simultaneously tempering the underlying material, due to the extended time at temperature required for the Nitriding process. http://www.awgolf.co.uk/ It seems to me that these features would be beneficial in a gun barrel. The base material would likely be in the 36 38 HRC range due to the temperatures required for Nitriding.
The first barrel you list would bewholesale golf very similar to the nitrided one in base material, but would not have the Nitriding process done at the end. This barrel would likely be in the 36 40 HRC range.
Photo by Martim Passos.