I come from an Aviation Maintenance background, so I understand the 41xx series of steels to a certain extent. I have heard quite a bit about the desireability of 4150 CMV has the "best" steel for AR barrels, and I'm wondering why that is.

Some of the explanations I've heard here, and on other internet forums is not correct. While 4150 has a higher hardening potential, due to the greater content of carbon, it also has a higher "brittleness" potential, again, due to the greater content of carbon. Which means it is less "malleable" than 4140.

So 4150 is not "tougher" than 4140, with "toughness" being the combination of hardness and malleability.

So, what is it about 4150 that makes it a superior barrel metal, especially with a hard-chromed bore? I admit to being unfamiliar about what stresses are put on a barrel, understand that a certain need for "hardness" is necessary. (One cannot prescribe Viagra to an AR15.) In other words, how is 4150 superior to 4140 with a hard chromed bore in dealing with the stresses produced by shooting?

Thanks!