Annealing "ring" ?

[Straightshooter1]

Its typically the Cu content that varies in cartridge brass. 68.5-71.5% by weight. Zn is 28.5%. The rest is Fe, Pb, and other trace elements.

Just more info along this line:

Cartridge Brass Alloys Revealed by X-Ray Spectrometers « Daily Bulletin

Are there significant metallurgical differences in the alloys used in various brands of cartridge brass? The answer is yes, and we have proof. Using a state-of-the-art X-Ray Fluorescence Spectrometer, some tech-savy Wisconsin shooters recently analyzed the alloys in seven different types of...

bulletin.accurateshooter.com

 

[RegionRat]

I share that opinion. But I would be willing to bet this - New Factory Brass loaded in the facility near Independence MO meets spec. And I am also willing to bet their analysis is much better than someone "eyeballing" it.

Annealing, new barrel break in, rifle barrel cleaning are all topics where if you ask 10 people you will get at least 12 "Expert" opinions.

Correct.
In the factory, keep in mind there were several points at which annealing is used in early steps, then again when subsequent steps pick up work hardening, and then the final time on the necks. Each of those annealing steps have specs.

The cases are typically sampled on a schedule, more often if there are any reasons like adjustments or disturbances. At several places in the process, the hardness is sampled to make sure the hardness stays within specs since we want more hardness in some places and less in others.

The process of controlling the hardness is used as a proxy for the other properties we care about because it is far easier to measure on the actual parts than it is to directly measure those more important properties like the strength and modulus values.

The point about most military ammo specs, is that they have no goal for reloading but they focus on the reliability for that one time use. It just happens that the properties that are good for the purpose happen to give some of the best properties for reloading (multiple use).

It would be difficult to improve on those properties in terms of making them better for multiple loading, versus the ones we pick for the primary purpose.

 

[Dave M.]

I share that opinion. But I would be willing to bet this - New Factory Brass loaded in the facility near Independence MO meets spec. And I am also willing to bet their analysis is much better than someone "eyeballing" it.

Annealing, new barrel break in, rifle barrel cleaning are all topics where if you ask 10 people you will get at least 12 "Expert" opinions.

I also don’t eyeball it, I have sectioned many pieces of brass and measured the hardness along the length of the sectioned brass.
Dave

 

[gdbleb]

I think it has to do with the finish and oxidation of the brass more than exact composition

Agree. I have accidentally tumbled Lapua brass overnight to a high polish and then annealed. Very little to no discoloration whatsoever.