For example, the AMP article is based on their a priori assumption that hardness testing is the only true measure of the results of annealing.
That assumption is interesting, but it's conjecture and certainly not a well established scientific fact.
Ideally, for the purposes of a cartridge case, one wants brass to maintain a certain hardness. The problem with work hardened brass in that application is not necessarily the increased hardness, but the loss of ductility and potential development of stress fractures.
To simply maintain that Salt Bath Annealing has no effect on brass denies the actual results of actual users experience.
They don't claim that hardness testing is the "only true measure of the results of annealing". It is however a good measure, and a Vickers microhardness traverse is a particularly good method for assessing the extent and consistency of annealing along a sample. It is widely used by metallurgists, and I've personally done lots of them for this and related purposes. For a given sample of cartridge brass, as we anneal hardness drops and ductility rises. As we cold work, hardness increases and ductility drops. They are opposite sides of the same coin, so hardness testing is a really good proxy for ductility in this particular application.
The authors of the article didn't claim that salt-bath annealing had no effect. Their results were that it did not adequately anneal case necks, even where time and temperature were such that case shoulders and body were over-annealed. They also point out that it is hazardous. Nor did they claim that their machine is the only method by which cases may be annealed. This is a straw man.
