If the barrel is 4140 chrome moly with a RC range of 30-35 it sounds like they did it within standard range, not too soft or hard. If it is any harder it gets into brittle range which could turn the barrel into a fragmentation grenade instead of bulge under too much pressure.
I know absolutely nothing about this stuff but google is my guide
Comments from several sources.
Most barrels for use on hunting rifles and in military firearms are made from a high alloy Chrome Molybdenum steel of the sort used in high stress components such as truck axles, conrods and such. In the United States these steels are designated as 4140, 4150 and 4340 types
(I had an unfortunate hard slam encounter with a curb and bent an axle shaft in my mustang. Wonder what grade of steel it is? Destroyed the aluminum mag shaving a inch thick and 3 foot long blade off the rim. )
Rc 32, the upper end of the hardness range that still readily permits the types of machining operations involved in making barrels.
Elasticity must be maintained in gun barrels, and the range of 26-32 Rc (Rockwell C scale) hardness has been determined as the appropriate, safe tradeoff
Tensile strength and hardness affect barrel performance. Tensile strength is the force required to break a steel rod one inch in cross-sectional area by pulling at both ends. Generally, hardening steel increases its tensile strength. But a tensile rating of 100,000 pounds for a rifle barrel is worthless if the steel is so hard it's brittle. A hardness of 25 to 32 on the Rockwell C scale has proven a useful compromise.
Generally speaking, the tensile strength of a steel can be increased by hardening it. But as the hardness is increased, so the steel becomes more brittle and it becomes more susceptible to fracturing from a hard knock or sharp impact - or setting off a small explosion inside a tube of the stuff! A trade off must therefore be made of tensile strength against impact strength and for barrel steel the resultant hardness settled on is usually between 25 and 32 on the Rockwell C scale.
Quick summary of checks I have made over the years:
Older vintages of military Mauser barrels and early 1903 Springfield .30/06 manganese steel barrels around Rc 10.
Later Springfield .30/06 barrels made from what P.O. Ackley said was "WD4140," WD meaning "War Department", was around Rc17, the average hardness of "normalized," ie, air cooled 4140 steel.
The majority of commercial barrels from Winchester, Remington, Ruger, etc. tested around Rc 24-26, while at the time I tested them, the Savage 110 barrels were right up there at around Rc 30-32.
Shilen barrels at the time were Rc 19 while Douglas was around Rc 25.
Current Shilen barrels run around Rc 29-30.
Most 416 stainless rifle barrels are around Rc 20, +/-.
As you can see, barrel steel hardnesses range all over the planet, over the entire hardness range from dead soft annealed up through about Rc 32, the upper end of the hardness range that still readily permits the types of machining operations involved in making barrels.
an opinion supporting obiwan position
The 4140 used for these barrels have a hardness of Rc 26-32. This is a wide range, thus why some last longer than others. Chromelining has a Rc ~70 and a Combloc barrel Rc ~40 (usually). If these barrels were Rc 30 and chromelined = GTG, but their not.