I couldn’t tell you the hardness but I can tell you this .
CVA barrels will eat your gravers up . Literally you will spend a lot of time sharpening . In fact just about every inch you will need to touch up the angles .
This is what I find so odd about all the roomers about those barrels being soft . Even cobalt tips just disappear. They last just as long as M42 or high speed steal in what ever Jukar is using and cost 3 X as much .
GM barrels cut very nicely and the ones from rice and Getz gut even nicer .
I find that plain old cold roll is the best to start on if your going to work on barrels .
Yes its a lot softer but you will learn to keep you angles while at the same time be able to feel when the your point is getting dull .
The thing that I have learned is that the harder the steel is , you need to change the geometry of the point , kinda like a wood chisel . Just as each wood is different so is each metal.
With soft woods you want a shallower heal . This keeps the chisel from diving on you . But when you go to harder woods a steep heal will help hold the chisel in the material and keep it from jumping out
Same with gravers . When the metal is hard , a shallow heal must be watched or it will want to jump out and you will get over runs .
Go to Steve Lindsey web sight . Read all you can . While he mostly about Pneumatic hammer gravers , it’s the same process as chase graving or push graving .
There is a wealth of knowledge there with folks from Remington , colt all the big names . These guys are the very people who in this country do work that demand 10 to 100’s of thousands of dollars just for their engraving or charge thousands just for a 1 to 2 day class
BUT I have found All of them are willing to help you out with questions . Pointers , information no mater which of the 3 different tools you chose to use ..
These folks know the full scoop . don’t be afraid to ask the most basic of question .
Steves forum , is very much like ours here . There is less traffic but they will answer you
http://www.engravingforum.com/forumdisplay.php?f=2