Thursday, June 11, 2009

Annealing case necks.... a simple and safe method

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(This blog is mostly about journaling my own adventures in learning. As I love my hobby with a passion, so do I love the learning process that comes with it. If someone else can profit in their enjoyment by my scribbling, then that’s icing on the cake. That’s what this article is about… a description of some of what I have learned regarding annealing brass case necks. As always, click on any images to enlarge them.)

So… what is annealing, and why bother with it?

Different metals react in different ways to stress and pressure. Steel, when heated to the correct temperature and cooled quickly (quenching) will grow harder. This is called heat treating. Reheating it to a certain temperature and letting it cool slowly will make it less brittle, and is called tempering. Aluminum does something different, as does lead, and so with brass.

Brass does not harden with temperature, but with ‘work’. As it is stretched, pressed, and sized it becomes harder, and more brittle. Simple age has a similar effect on brass. Taken too far in the process, brass will crack and fail. That’s what happens to cartridge case necks as they are reloaded multiple times. It’s especially prevalent with high power bottle neck rifle cases, and even more so with those getting heavily resized with each loading.

One of the features of brass is that it can be ‘annealed’, or softened with heat. Heated to a certain temperature, it becomes softer and less prone to cracking. The effects of many reloadings and firings can be negated with a single annealing process, allowing the cases to be reused far beyond their normal life span.

Annealing is also a pet technique of the long range precision bench rest shooters. These folks cringe or celebrate over a quarter inch group variation at five hundred yards. To them, annealing the case necks is a standard part of the hand loading process, as they aim at ‘precision nirvana’.

My reason for wishing to anneal case necks…. is that I’m too cheap to buy new brass. The Grand Old Turk I shoot in the rifle matches has a set of hand loads worked up on cases made in 1944. They were used when I got them, and I’ve since loaded them eight or ten times. They are starting to show their age! The last match I fired, I lost a case due to a cracked neck… and that means they are all ready to do the same. A new matched set of brass would cost me mo..mo..mo..money, and that is not acceptable if I can avoid it. Finding once fired and reloadable 8x57mm brass on the ground at the range… well… I won’t hold my breath waiting for that to happen.

Doing a Google search on ‘Annealing case necks’ will return thousands of hits, and at least a few of them will be scholarly works on the metallurgy of the process, and how to do it correctly. It’s not a mystery process, suited to hooded monks working in mystical caves. The only discussion that matters is in the process itself, with the real question being this: ‘How can it be done safely, uniformly, repeatedly, and for a reasonable price?’

There’s a dozen ways to do it, and many of them are workable. Some are downright dangerous, and one or two are impressively high tech (and expensive). This article is about the method I worked out for myself, being a compromise to reach my simple goal. I’ve borrowed points and ideas from several sources, putting them together into an easy process that appears effective, safe, and inexpensive.

The temperatures used are critical, for several reasons. Foremost among them is safety, as the lower body and base of the cartridge case must never be annealed and soft. If it’s heated above 480 degrees or so, the grain structure of the metal will change and the case may not be able to contain the pressure of firing (think face full of flaming debris). On the other hand, the case neck must be heated to about 750 degrees for some seconds for the annealing process to take place. Doing one without doing the other is the real trick.

The next problem is actually judging the temperature correctly. Some folks swear by working in a darkened room and judging temperature by the color change of the case. In other words, they watch it turn dull red under the flame, and then quench to stop the heat spreading. The problem with this method is one of judgment and timing. The line between ‘dull red’ and ‘turning orange’ is only a few degrees and a few moments in time. Over-annealing the case will make it too soft, and ruin it.

I found and use a ‘Tempilstik’ to judge temperature. This is a chalky crayon type of marker used by welders and metal workers. Rubbed on the metal to leave a mark, the material will melt at a relatively exact temperature. It costs about $11.00 at most welding supply stores, and is usually in stock. They come in varying temperature ratings, and I chose 650 degrees for this use.

I found it’s best to work with dirty, as-fired cases. Brass cases freshly cleaned are very hard to mark with the chalky Tempilstik, and the cases need to be cleaned and sized after annealing in any case.

Using the temperature sensitive marker, draw a line of the material around each case about ¼” below the shoulder. During heat treating the neck, the heat will soak through the brass to the body, melting the marker when it reaches 650 degrees at that spot. The neck will be hotter, and should be in the correct range for annealing. It takes six to eight seconds for the heat to soak that far, and that’s long enough for the annealing process to happen. I found that even a faint line of Tempilstik is visible while the case is spinning, and not much is required. The state change from solid to liquid of the indicator marker is readily visible under good lighting.

The cases are slowly spun in the flame using a battery powered drill/driver with a low speed setting. As a case holder, I used a 1/4” drive shallow 1/2” socket, with a 1/4” bolt inserted through the square drive hole and a nut tightened in place. The shaft of the short bolt that protrudes can be chucked into the drill/driver snugly. Spinning the case within the flame makes for an even annealing process, and is the biggest reason I opted away from the ‘pan of water’ method.

The process works like this:

Have a propane torch standing on the bench. It works best if the short and squat cylinder is used, giving the torch a wide base to stand on. Have the torch running full blast, with the flame pointed away from you (and NOT at flammable objects!).

Have a small pan of water on the bench just in front of the torch, placed so the case can be tipped into it from the holder once proper temperature is reached.

Have the case holder chucked in the drill/driver, and the tool set on its low speed ‘driver’ setting. Begin spinning the case before it’s moved into the flame.

With the case spinning, move the neck into the flame until it’s fully enveloped. Make sure the flame is pointed from the base of the case to the mouth, and the flame washes away from the body of the case. Do not have the flame wash over the Tempilstik marking as it will melt at once, no matter the actual temperature of the brass case.

With the case spinning, and the neck enveloped in the propane torch flame, watch the temperature indicating marker. Once it melts, tip the holder forward and dump the case into the water.

That’s it. The case is now ready to be sized, polished, trimmed, and reloaded.

It’s advisable to practice the process on scrap cases until the timing and rhythm is learned. I went through half a dozen junk 30-06 cases as I learned how to hold the case in relation to the flame and for how long. Once this is worked out, repeatability is good and a large batch of cases can be done quite quickly. It takes longer to scratch on the marker than the actual annealing process takes.

Annealing case necks is not something that needs to be done often, unless extreme precision is the desired outcome. For rifle cases that are to be loaded more than a few times, it’s a good technique to use. If the shooter is forming cases through a multi-step die process, annealing the necks is a must-do step. For ancient brass, unusual calibers, or perhaps for those of us just too cheap to buy new cases…. annealing can save the day.

25 comments:

keith said...

Does the annealing process permanently discolor the case?

Great blog, by the way.

Keith

Carteach0 said...

The cases can be polished bright again if desired, but I've not bothered. I run them in the polisher till they are clean, and thats enough for me.

Besides... I'm kind of enjoying the fact that I can point to the coloration and say "I did that".

YeOldFurt said...

Good post. I use the melted lead process which works for me.
YeOldFurt

immagikman said...

As a former electronics tech, I see another step you could take to protect your brass, use a deep well socket, it will act as a heat sink and keep the temperatures of the lower sections manageable. We used to use this principle to keep from ruining chips and transistors when soldering. You attach a metal heat sink between your work area and the area to be protected. The more massive your heat sink the less thermal shock to the protected metal.

Carteach0 said...

I approach it differently than the heat sink principle. By aiming the flame away from the shell body, it's only source of heat is what soaks down from the neck. Once the temp-stick melts the case is dumped into a cooling bath and the annealing is shut down.

If I physically attached the shell to a heat sink, it would be much harder to dump it into the water, and would really slow down the process a great deal.

The heat sink principle is why some people do their annealing with the case already sitting in a water bath. The reason I didn't go with that is I wanted the case spinning to anneal the neck evenly.

It's still a valid suggestion, and worth considering.

KelTex78 said...

I don't know how much of a heat sink you are going to get since it is just relatively loose in a socket. If it could be clamped so there was a large amount of surface area contact, then it would be a better sink. One other possibility would be to quench the case in oil instead of water. The water boils which creates a barrier of steam which slows the cooling. An oil bath will allow the case to cool more quickly. Not sure if that would be needed for quenching cases though...

immagikman said...

Yep I understood your idea and rotation is an excellent idea, the deep well socket is just modifying the basic method you already use to add a bit more protection without "attaching" a honkin piece of metal :) Might have to tip it farther to get it in the water though.

In any case I like your method better than most that I have run into (not that I do a lot of this kind of thing)

TJP said...

I have to admit that the socket is a new twist. It sure beats having a custom die made for every caliber. I'm a cheapskate too, but at 40 cents a case for garden variety brass, it's also very smart to keep your cases going, if the process is reasonably simple.

My brother is fond of saying, "I'm glad I started loading pistol calibers first, because if I loaded rifle I'd probably have quit." The 40 cent case is just the starting point. Think of all the work that goes into prepping new brass for a long-chamber milsurp gun.

I have a bag of .303 that I want to prep for my oldest Enfield. It's been sitting there for a few months now, because I'd rather pull the handle and get 45 Colts. I've only trimmed the 45s once--heck, I didn't even bother sizing the ones that will hold a .454" bullet.

Or I guess I could load like some videos I've seen on the Internet: just skip all the steps and do it Foxwoods-style, yanking on that lever like a Granny sitting in front of a one-armed bandit.

Old NFO said...

Excellent post Carteach0! Thanks for the education.

RKL said...

That's a great post!

I only reload handgun cartridges right now, but I would like to start reloading rifle cartridges in the future. I think you've got a great method worked out.

RKL

Johnnyreb™ said...

Awesome post, thanks for the explanation. I seem to have forgotten that annealing is about the opposite tempering ...

Peter said...

Yet another post of yours to bookmark. :-) Thanks for sharing your knowledge; it's helping me get into reloading.
I noticed you said it takes longer to mark the case with the tempilstik than it does to anneal; what about marking it while its spinning? I've never used tempilstik, but from your picture, it looks like it doesn't go on very well; perhaps marking while spinning won't work.

Firehand said...

Wish I'd thought of the socket; would have saved some singing when I annealed some cases formed for 7.62 Nagant.

But I'll remember it for the future

Eric said...

Here's a real real easy way to anneal case necks, if you cast your own bullets. Leave the spent primer in the case, hold it by the base and dip the mouth of the case into the lead until it's just at the start of the shoulder. Lift it out, if lead sticks it's not hot enough. If the lead doesn't stick, it's done. Throw the case into some water and you're done. If the case gets hot enough so you feel heat in your fingers, you've heated up the case too much. Throw it out. I have used this method to anneal 45-70 cases to make 8mm Siamese Mauser cases. NOTHING works better. Haven't lost but one or two this way. 45-70 to 8mm Siamese mauser is tough, take the 45-70 to 348 winchester, relube and goto 33 winchester. It's a lot of brass movement, and works perfectly with the lead trick.

Nickname unavailable said...

I bought the TempilStick but found it frustrating to get it to stick to the case, so I bought Hornady's/Tempilaq annealing "system", with the caseholders (I'm sure the sockets work as well or better). http://www.midwayusa.com/viewProduct/?productNumber=360902
One of the differences that I like is the brushing-on of the Tempilaq is easy and easily visible. I was stimulated to join this discussion because of another difference though; the difference in the temperature of the Tempilaq is 475 degrees vs. the tempil stick that you have used at 650 degrees. That is a considrable difference. I recognize that the brass has to reach 650 for a short period of time to affect annealling but do you want it annealled that far down and if so why do you think that Hornady would recommend the 475 degree temp indicating "paint"?

Carteach0 said...

Nick Unavail,

I can't answer for the temperature chosen by Hornady, but I chose mine based on readings of metallurgy reports on the web, and discussions with a materials engineer (and bench rest shooter). I will say the method I hit upon leaves me with exactly the same marking and coloration as mil-spec ammunition, if that is any guide.
If Hornady is specifying a longer heat-on-neck time, then that might account for it as well. The case necks can be annealed with a high temp for a short time, or a lower temp over a longer time. Of course, keeping the heat applied to the neck for a longer time means more time for the heat to soak towards the base of the case. My method only has the heat applied for five to seven seconds.

As for the temp stick.... I went with that for two reasons. The liquid costs more, and the welding supply store did not have any (g). Yes, it can be difficult to apply, but I found that even a very thin coat shows up well when the case is spinning in the flame. It doesn't take much at all.

andrew said...

interesting to see this, i use barnes copper bullets and getting the neck to hold them firmly enough is a problem so i have annealed the neck by turning it in a gas cooker flame for 32 seconds

then transfer immediately to the decapping and neck sizing die while its still warm

i don't like the lead method, new research shows that any amount of lead is a problem, one of the reasons i hand load is to use lead free bullet sand primers

Suburban said...

I had read the 6mmbr.com article on annealing, and I bought the 650 degree stick, but then I didn't know how to use it. Thanks a lot for explaining how to use it. I was putting it on the neck, and just like you said, it disappears as soon as the flame touches the case.

I'm trying to anneal .223Rem/5.56mm cases. I say "try" because I haven't been able to get the blue color that I've seen posted several times. The best I can manage is either a light brown or black. The light brown doesn't seem to do any harm, but may not do any good either. The cases that turned black, or almost black were overheated, and crush like a soda can when I try the vice-grip test.

The yellow chalk line melts away after about 3 seconds, I would guess. That's a shorter period than the 5 or 6 seconds I've heard several people speak of.

I think I need to try a higher temperature stick, and some practice.

Thomas said...

Question about the rotational speed. "Slow drill speed" is about ballpark how many rpm or turns per second, would you say the way you do it?

Carteach0 said...

Thomas,

My amateur methods did not prompt me to check the RPM of the drill/driver set on 'slow'.

My unit is a variable speed, and I do practice trigger control as I use it. My rough guess is 60-100 rpm.

Bill said...

I love this article and have shared it on forums and read it several times over.

I have one discrepancy/question. Any heating of the case body and head above 482 degrees Fahrenheit is considered dangerous, no? 482 is the temp at which molecular change begins to occur in the brass.

So even if the temp stick mark reaches 650 and the case is quenched how do you know the head or body didn't reach a critical temperature?

Carteach0 said...

Bill,

I don't, not completely. It's a scary thought.

On the other hand, one can watch the temperature progression down the side of the brass case while performing this trick, and seeing how long it takes the heat to reach 650 at the base of the neck is a solid clue how quickly it's rising. Quenching at that point, quickly, shuts down the process.

I strongly recommend practicing with some junk cases before moving on to good ones, and reserving heavy loads to new or once fired cases.

Gary Cody said...

Gecko My shooting buddies and I have been using the pan method for many years. We load about 300 rifle cases sitting upright in bread pans, place them on the bottom rack of a pre-heated oven, and then carefully fill the pan with water up to about ¼ in. below the case shoulder. Then turn the oven up to high broil (top heat element) and allow to heat-up for 5 minutes, developing 525-540 degrees usually, … then turn heat OFF and allow cases to remain in oven another 5 minutes before removing. Pour all cases into a large container (or sink) nearly full of Cold water. Drain off water, and then process your newly annealed cases. Like I say, this has worked well for us for years.

Anonymous said...

i am a tool and die maker and years ago i worked for a bullet company, i use a lee lead pot to temper small heat treaded die's, so i started using the lead pot to anneal the necks, worked great dipped the neck in 2 to 3 sec. then put in warm water, i did alot of 223, and 308, just wear a glove and make sure the case,s are dry. its a very even heat so there is no spinning

Jason Atkinson said...

Great post. Glad I found this blog. I also use the socket method but I've always used a deepwell for more control. I turned my necks and they can become dead soft very fast because the neck wall is only .0085 thick. In the picture with the torch though I have to point out a variable that is overlooked. The type of torch matters as well as the angle and the part of flame you use on the neck. The hottest part of the flame is the tip of the blue flame cone. I always put the flame at about 45 degrees facing away from the body and put the neck right into the tip of the blue flame for only a few seconds. The brass should have a slight pink finish on the neck and a perfectly even tempered ring into the body after its cooled. I never cool in water. I place them standing up on a piece of thick stainless steel bar stock. Brass is suposed to be almost not affected by rapid cooling like steels are but in competion accuracy even slight variation is unacceptable which is why I use a thick steel to set the hot cases on instead of dealing with the almost nonexistent thermal shock that does occur. The variables that a person will encounter can be mitigated by doing the job indoors with the same lights on and doors and windows shut. It all comes back to the need that makes us anneal...repeatability. It may be for accuracy or extended brass life. Doing it the same everytime will provide the most consistant result.

Also...
Dead soft necks are not always bad. It gives minimal neck tension but that may be the goal of a benchrest shooter with a custom chamber fit for turned necks. It also allows the neck to grow longer faster which is a plus for making long neck wildcat cartridges. It even helps some poorly designed cartidges that have thick necks and split often such as the 243 wssm. Think about this. Annealing is a varying process and you will have differing hardness from one to the to another with almost all methods. Dead soft is just that. Dead soft is closer to consistent than anyone can anneal to without a controlled automated process.