It's not my opinion that it produces inconsistencies. That's a provable fact. I'll admit it is my option on whether it's "too many" and that you'd be better off not annealing, as that's absolutely subjective and a matter of perspective. But yes, that is my opinion based on many years of experience with annealing. You and anyone else are free to take it or leave it. I'm here to help, if I can, not push any personal agenda. I fully understand everyone's needs and standards are different, and that's just fine by me. I know there are many people quite satisfied using a torch to anneal and many methods of putting the case into that flame.
And to elaborate further with some points regarding brass cartridge flash annealing:
I've seen a lot of people across many social media platforms say things like brass tempers when quenched (like steel) or anneals when quenched (like copper). This is simply folks mixing up the characteristics of both copper and zinc to C26000 cartridge brass. A lot of the following information comes from legitimate metallurgy reports, US Army studies, University reports, AMP's own findings and a few personal tests.
Several folks have stated that when annealing any glow to the brass at all means that the brass is now dead soft. Cartridge brass, C26000, starts glowing at 950F. So again, will brass become dead soft when glowing? The answer is yes and no. Heat and time with annealing cartridge brass have an inverse relationship which means the hotter the brass the less time is needed to anneal, and the lower the temp the more time is needed to anneal. So leaving a piece of brass at 950F for 10 seconds, it will have become dead soft, where as if you anneal for 3-4 seconds and it reaches 950F or slightly above for a split second, right before it is taken away from the flame or induction field, you will be completely fine (these are not exact numbers, just an example). Brass is a great conductor of heat, thus it will cool down quite fast below temps that are needed for "flash Annealing", which is what we do. I myself used a socket, drill, and torch, an Annealeez, and now have two induction units: a Fluxeon Annie induction annealer and an AMP Mark 2. When using the AMP's Aztec mode I can tell you that most of my brass does have a slight glow to it that can be seen with the lights off: 6.5 CM, 6.5 PRC (Hornady and ADG), 243 win, 6x47 Lapua, 270 win, 223 Rem, 308 win, 338 Edge, 338LM, 7 RUM and 7 RM, 300wm, 300 PRC, etc. There are only a few that I anneal that don't have a slight glow when pulled out of the AMP. Additionally with my Annie annealer, I Hardness Vickers tested some samples of brass I annealed that had a slight glow. The average HV was 97, which is exactly in the area it needed to be.
Dead soft brass means that the brass has achieved all three stages of annealing:
- Recovery
- Recrystallization
- Grain Growth
If you're curious on the three stages characteristics feel free to look them up. However, Grain Growth is where the brass becomes dead soft. When we flash anneal we want the brass to have achieved recrystallization, but not entered grain growth. Also, I say flash anneal because you can anneal at much lower temps, just under 500F, but that takes hours and doesn't allow you to focus the heat specifically on the cases neck. Induction and Flame will achieve the first 2 stages of annealing with ease.
Salt Bath Annealing, on the other hand, only achieves recovery stage.
Cartridge brass having a slight glow and being ruined isn't an absolute. If annealing in seconds, your brass neck should be north of 750F. I typically waited until 750F templaq had melted an eighth to a quarter of an inch past the shoulder body junction with the Annie annealer. The neck was well above 750F at that point.
The big problem with any form of annealing is determining how much energy to apply in order to achieve the correct neck and shoulder hardness. That is not a problem for case manufacturers, because they all have labs where they can test for the correct results when they set up for a production run of a new lot. Most manufacturers of top-quality brass use induction these days, so it is a one-time set up each time. The older torch/flame systems required a bit more monitoring. The important thing here is that it is the annealed hardness that matters, not the actual temperature which achieves it.
The problem for the reloader is that most don't have, or have access to, micro-Vickers hardness testing equipment, which is very expensive, and also requires expertise to operate. They therefore have to use a proxy to try to achieve firstly the correct hardness, and then repeatability. There is no precise and reliable way to do this. In AMP's early R&D they cut away part of the inductor housing to allow thermal imaging of the cases being heated. This was done with live thermal video so that time and temperature could be recorded. You can see some of the results in their Part 1 study here:
https://www.ampannealing.com/articles/40/annealing-under-the-microscope/ .
Thermal imaging itself has problems though. Because of the reflectivity of brass, you tend to get poor readings. They had to spray paint each case with black bar-b-q paint in order to get reasonable readings.
Most reloaders who are using a torch rely on Tempilaq as a proxy to find the "correct" temperature. Most use 750F as the goal. For a start, that temperature is way out. Secondly, Tempilaq is subjective. Judging when the color change is "just right" can vary by +/- a second or so depending on the observer, meaning huge variation. Flash annealing, which again is what this is, happens very quickly. Peak temperature only occurs for a fraction of a second. There is nothing wrong with Tempilaq as a product. It just wasn't created for this application.
Other reloaders use the instant that the flame changes color or when the case begins to glow red, as the correct setting. Again, it is a "best guess". Even if the correct hardness is achieved, unreliable gas tank pressure etc. can mean that the flame is not necessarily consistent for an extended annealing run. When setting up again for a new run, there is no guarantee that the same setting will be achieved again. Many of the top shooters – world champion F-Class, long range benchrest etc. have actually decided that no annealing was better than poor annealing, and had given up before the AMP annealer came along. Lou Murdica, for example, is one of those guys.
AMP's AZTEC mode was developed over the better part of a year, and involved collecting countless data in the lab. It is extremely accurate. Even now, if a new cartridge or wildcat is introduced to their system, they require samples so that it can be correctly calibrated. That is a one-time process though, and AZTEC will then give the correct results for that cartridge regardless of brand, lot number or neck turning.
As for tolerances, the AZTEC settings target an annealed hardness of 98 HV +/- 2 HV. If the brass is good enough, that is what you will get every time. Any variation is due to actual variance in your brass. Check the Part 3 study, here:
https://www.ampannealing.com/articles/46/annealing-under-the-microscope/ for that data. They found that if tolerances are worse than that, and the hardness is say 110 HV on the high side, or 90 HV on the low side, that will show adversely with results on target down range. A variation of +/- 10 HV would be considered pretty good using a torch.
Also, brass does not get harder when quenched. That is a characteristic of steel, not brass. Quenching has zero effect on brass other than cooling it down quicker.
Hopefully if anyone actually took the time to read all this, it's found as helpful, and clarifies my previous comment.