Good information on annealing

[MarkInPA]

I became interested in annealing in 2021, and like you was dismayed by varying opinions in the shooting community. Due to my engineering background, I then turned to the scientific community for information and discovered that much of the information on annealing, propagated in the shooting community is erroneous, mostly due to a lack of understanding as to the physics underlying brass annealing. I discovered the following:

1) The microscopic grain structure of brass changes as you work it, making it harder and more brittle.
2) Heating brass for a sufficient amount of time will change the microscopic grain structure of brass, returning it to its pre-worked state.
3) Brass begins to glow at a specific temperature (between 950ºF and 1050ºF depending on the exact composition) and melts at 1710ºF.
4) Brass cannot be "over annealed"; that is applying additional heat/time does not further change the microscopic grain structure beyond a certain point (unless of course you melt it).
5) You only want to anneal the neck and shoulder of a case, and not the base, so the shorter the annealing time, the less heat will be conducted down the case to the base.
6) Quenching brass does not affect its microscopic grain structure in any way.

Annealing brass is a function of temperature and time. The 700ºF that is often propagated among shooting community as the proper brass annealing temperature actually needs to be maintained for 1 hour to anneal brass. The following formula is used to calculate the time and temp to anneal brass:

B=1.38065x10^-23 (Boltzmann constant)
E=0.327x10^-18 (constant for the material, in this case brass)
T1 in Kelvin = 644º (700º F)
t1 in sec = 3600 (1hour)
T2 in Kelvin = target temp
t2 in sec = time to anneal

t2=t1*exp^(-E/B*(1/T1 - 1/T2))

This is easy to plug into Excel and if you pick 810.9ºK (1000ºF) for your target temp you will anneal in 1.88 seconds. Again note that brass starts to glow between 950ºF and 1050ºF depending on the exact composition. Using 900ºF changes the required time to 16.1 seconds.

I use the glow of the brass to gauge my temperature, understating that I am not going to over anneal if I keep it there for 2 sec or 5 sec. If you want to be more precise with the temp then you can invest in an infrared thermometer. I cannot stress enough that the key to annealing is getting the brass to between 1000ºF and 1200ºF for a few seconds (remembering you cannot over anneal unless you get close to its melting range), ensuring it is not under annealed.

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I think part of the problem is that by far most of us don't have a background in metallurgy that appears like you do. Combine that with the fact that there is very little formally written about the subject from reputable sources and it makes some of us hesitant to jump in. It would be great if you would see something written about the process in a reloading manual. I checked mine and I think there was only one that briefly mentioned it but, they did not go into detail about the process. At some point, we need to have faith in what we are being told. Its just that you want to make sure you are listening to a credible source before you make that leap. I kind of feel like a little kid standing by the edge of a pool. Trying to work up enough nerve to jump in and swim.

 

[M1A1ABRAMS]

I think part of the problem is that by far most of us don't have a background in metallurgy that appears like you do. Combine that with the fact that there is very little formally written about the subject from reputable sources and it makes some of us hesitant to jump in. It would be great if you would see something written about the process in a reloading manual. I checked mine and I think there was only one that briefly mentioned it but, they did not go into detail about the process. At some point, we need to have faith in what we are being told. Its just that you want to make sure you are listening to a credible source before you make that leap. I kind of feel like a little kid standing by the edge of a pool. Trying to work up enough nerve to jump in and swim.

Perhaps this is more on the lines of what you're looking for ?

Annealing Temperatures For Reloading Brass Cartridge Cases

G. Chambers, Ballistic Recreations Introduction Although the metallurgy of brass has been extensively studied and understanding is quite advanced at the academic and industrial levels, technical kn…

ballisticrecreations.ca

The Science of Cartridge Brass Annealing

Want to know how annealing brass works? We examine the science here.

bisonballistics.com

The Pros and Cons of Annealing Brass Cartridge Casings

When it comes to reloading ammunition, the process of annealing brass cartridge casings is one of those topics that raises varying opinions among firearm enthusiasts and professionals alike. Annealing, which involves heating the brass to a certain temperature and then allowing it to cool, is a...

www.canadabrass.ca

 

[MagnumManiac]

The biggest problem I see is no one seems to have a way to quantify what they are doing and that is what causes me to stop and pause.

Oh yes we do.
I run my brass through a Rockwell hardness tester. I get a benchmark, then stick with it for the life of the brass. Annealing can be too little or too much, which gives poor spring back and tension. If you believe your un-annealed brass is staying the same after each shot/sizing, then you aren't sizing dozens of cycles.

Cheers.

 

[MarkInPA]

There has been some good information provided here. For sure. I thank all who participated. For now, I think I'm going continue without annealing. It just seems like there are still too many open questions. I think I may be a little like you Mark. Just don't shoot enough to get that concerned about extended life of the brass. I was looking at this as a way to perhaps increasing accuracy if ever so slightly. And maybe it would be nice if I had brass that was a bit more elastic and maybe get more consistent measurements coming out of both the fired brass and the sizing die.

I'm just not feeling comfortable with it yet.

 

[Buckskinner]

A quality sizing die set up properly is key whether you anneal or not. I have switched most of my dies to Short Action Customs bushing dies which has made a world of difference in controlling neck tension/shoulder bump and to minimizing brass working. Of course there are several quality dies out there these days.

I did make this annealer several years ago and it works well and is repeatable but really haven't seen the need to use it since changing my sizing procedure.