Neck Cracks

[Ron AKA]

If you look closer you will find virtually no credible published information on what temperature to use in the first place. Lots of claims and suggestions, from Hornady's 475F to people who want a visible glow (about 800C), but I challenge you to show me one source that actually has a strong arguement as to why the temperature they give is correct.

I agree, it is hard to find good information on the net, and it is getting worse. However after a little searching I found a Technical Data Sheet for C26000 brass, which is what is used for cartridge brass. There is one graph where they show how much a work hardened sample reduces in hardness in two minutes with various annealing temperatures. It shows brass with three different starting hardness values. If you take the hardest one at 150 HV as an example (see graph below), the way I read it is that if you anneal at 435C you will reduce the hardness to 110 in 2 minutes. The lower starting hardness samples reduce less.

They offer a correction factor rule of thumb for longer and shorter annealing times, and say "Temperatures at 1 minute annealing time will be 10 degrees higher". So you would need 445C in my example if you want to anneal in 1 minute. I suspect most do not want to anneal each case for 1 minute, and if we assume (not always a good thing to do) that each time you half the annealing time you need 10 degrees more temperature, that means you need 40 degrees more to anneal in 7.5 seconds, compared to 2 minutes. In the example I gave, that means you need 475C or 887 deg F to anneal in 7.5 seconds. The graph is included below for your analysis of what it means. Perhaps you will come up with different conclusions.

What I decided is that it is not a black and white issue. The time and temperature to anneal is based on how much the brass is work hardened, and to what hardness you want to get to. I have a feeling though that there are many reloaders that are simply wasting their time annealing because they are doing it at too low a temperature and for too short a time.

As for Hornady's 475 F, brass is never going to anneal at that temperature. They however are applying it down on the body, so must be counting on the neck being much hotter. How much? Sounds like a terribly imprecise method when you are measuring 475F and hoping the case is nearly 900F somewhere else. Visible glow in the dark is a much more accurate way of doing it, in my opinion.

 

[BattleRife]

Ron AKA, I will grant you that seems to be a much better researched and more believable bit of data than the vast majority of what I have seen. Where did you get it? If it comes from a brass supplier I think we could probably certify it genuinely "credible".

While I normally would be very hesitant to take a data set for 1-2 minutes and extrapolate it down to 5 seconds, in this case it seems to compare reasonably well with the 550C that I have settled on as the best annealing temperature for my purposes.

 

[Ron AKA]

Ron AKA, I will grant you that seems to be a much better researched and more believable bit of data than the vast majority of what I have seen. Where did you get it? If it comes from a brass supplier I think we could probably certify it genuinely "credible".

Aurubis Stolberg GmbH & Co. KG

"Aurubis Stolberg GmbH & Co. KG with its 400 staff members provide a reliable and flexible partnership which guarantees the best performance, producing high precision copper and copper alloy strips and wire for the international market.
Aurubis AG, Hamburg is the largest copper producer in Europe and the global leader in copper recycling. With 16 manufacturing sites and four slitting centers, Aurubis is now represented in 22 countries in Europe, Asia and North America and offers jobs for a total of 6.500 employees."

Perhaps they supply brass to Lapua...

 

[Purple shoulder]

When I anneal I set the speed of my little home made machine to heat until the flame just starts to get orange traces and then shorten it by a fraction of a second. The case never glows at all, even in the dark. Then it drops onto a slide that drops it immediately into water. I'm told this sytem is a waste of time, but if i drop a pre-annealed case on the concrete floor, the case mount never dents. After annealing they will nearly always dent. I've got 22-250 cases that are at nearly 20 firings. Every time a neck splits (about every 5 firings) I stop and anneal the whole batch. I think doing it by hand or with a drill will work fine, but the consistency from case to case may be an issue.

 

[Ron AKA]

The case never glows at all, even in the dark.

You are probably well under 750 deg F. Brass anneals at that temperature, but it takes way too long -- perhaps 30 minutes. I think if you are properly annealing you should easily get to 5 reloadings with no cases splitting. But, that in part depends on how much you are working the brass from fired to full re-sized. It is worth measuring that, by measuring a fired case neck size, and then size it with no expander ball in your die and measure it again. That is the full compression cycle, and then it goes through an expansion cycle when the expander ball, the bullet, and finally the firing bring it back up to max size again...