Yeah but, 4150 and 4150CMV are not identical. The big difference; Mil spec 4150CMV has .25% vanadium, marginally less carbon than than 4150 (C=.41-.49...only marginally more than 4140 C=.38-.41) and other minuscule tweaks.
MIL-B-11595 E BAR METAL BLANKS STEEL BARRELS SMALL ARMS
Just had to look up what the CMV acronym brought...
We use tool steels in the 9% and 15% Vanadium content, but I'm sure the military feels that .25% must bring alot of wear resistance to the table too.
Originally Posted by hdwhit
That analogy may be overstating things somewhat. The range of alloying elements in 4140 and 4150 is identical except for the amount of carbon (40/100 percent vs. 50/100 percent, on average) and except at the limits of mechanical performance makes little difference, particularly in the case of a semi-automatic-only rifle.
It might be more apt to say that it's like someone who is only going to drive 30,000 miles in their lifetime comparing 75,000 mile tires with 80,000 mile tires. For most users, the theoretical difference in barrel life will be of interest only to the shooter's heirs.