Is there a temp to reach indicator ?
No, just the Aztec code value.
Does the hardness directly relate to a temp ?
The hardness is a result of the integration of Temp and Time, not just one or the other, but both. The higher the temp, the faster the change and thus less time could be used for a given goal. My personal preference was not to chase high power values in order to minimize errors in heat and to desensitize the time errors as well. As long as that concept isn't taken too far, you don't run the risk to the body getting too hot, but I always find that a very good trade.
WIth the AMP, there is only a code value change and they do not publish the algorithm to explain how it controls the time or power relationship. The manual states the following:
...
"As mentioned in "Analysis mode”, after a sacrificial case is analysed and USE is entered, the display will show RUN with a 0 and a * program lock to the right. The 0 gives the user that ability to customise their annealing even further.
To access the 0, firstly the * program lock must be opened. Just hold down the + button for two seconds and the * will disappear. Now the +/- buttons can be used to select up to six incremental adjustments up or down. + = more power = softer. These adjustments have been calibrated to give the same annealed hardness (HV) increments regardless of the cartridge. This means that the HV value per step is the same for say a 22 Hornet or a 338 Lapua Magnum. Each step represents approx. 2.5 HV, so that four steps will give approx. 10 HV up or down.
We always recommend that the ANALYSE generated code is used, because in our opinion it gives the optimal neck and shoulder annealed hardness. We do understand however that many reloaders will appreciate the ability to experiment."
...
I have been retired now for a few years, but I don't know of any system that actually controls on a temp setting for a cartridge neck. Thin brass is difficult in terms of radiometry and since the heat flux and time are easy, that was what we used to heat treat thin brass.
ETA: ..."is there a correlating chart so you know you only stress relieved or is it a guess ?"
I forgot to answer that last part and I think it is very important to mention this to folks who will try to research brass metallurgy on their own. We know that anything over about 530 deg F is a risk, but that isn't enough to get the job done either.
Keep in mind, there are huge differences in published values and tables between "bulk" materials and thin stuff like a cartridge neck or other tiny parts. There are also huge differences between standardized tests and methods, versus the science on tiny parts or thin necks.
Many texts and charts on the internet show slides and tables of properties for 70-30 cartridge brass. Those charts are typically showing bulk material properties measured by standard ASTM methods that require samples that are huge compared to necks. Most of those charts require oven controlled soaks at times and temperatures we cannot use for cartridge neck topics.
Those values are not wrong, but they also do not apply to thin cartridge necks or tiny brass parts with respect to time. In practical terms there is no such thing as a temperature only chart for what happens to a thin cartridge neck. (But folks can relax cause it doesn't matter)
While it is still always an easy thing to just take a large sheet of a thickness similar to a cartridge neck and soak it in the lab ovens, we saw differences in the properties compared to standard test (bulk) samples. Things happened so fast with thin sheets, that it becomes pointless to say that the time-temp values of bulk samples had any relation to what we did with small thin parts. Making the parts big or thick enough for accurate temperature measurement didn't answer the questions even if it did make for neater graphs and charts.
In the end, we use hardness values but the reason is because we can't do a practical tensile strength test in context, so we use the hardness value due to the coupling between those properties learned from the bulk standard samples. We don't try and directly measure temperature since we know the Draper point is relatively stable and we don't really care about hardness, we just use it as an indirect indicator of the yield strength. YMMV
