Another Annealing Question

[Ike666]

In an earlier thread about annealing Unclenick posted a link to a materials website:

http://www.matweb.com/search/DataShe...ac4e324&ckck=1

This gives the material properties of 70/30 brass, that used in casings. Scrolling down the page there is a section on Processing Properties where it gives the annealing temperatures (425-750 C & 797-1380 F). These temps are much higher than I had been lead to believe were necessary to anneal rifle brass.

I know that under-heating the brass will not accomplish the desired softening and over-heating will soften too much to form or make adequate casemouth tensions.

It seems to put the lie to the idea of annealing by putting brass in a standard kitchen oven.

The temp paste from Hornady says it is set at 475 F. This seems too low. Can anyone clear up this issue - what is the desired temp for annealing the casemouth and shoulder of .308 brass?

[g.willikers]

ammosmith.com has a good video on annealing.
It's under the videos/general reloading section.

[demigod]

Not to poop in your thread or anything... but why bother with annealing 308 brass??

I mean... it's common caliber. I pitch my rifle brass into the recycler before annealing would be needed. I can understand annealing hard to get brass, but 308?

[Brian Pfleuger]

It seems to put the lie to the idea of annealing by putting brass in a standard kitchen oven.

It's pretty well known by anyone who understands the process that putting brass in your oven, even at 300 degrees say nothing of "warm", is not going to hurt (or accomplish) anything.


Even at 425dg it takes HOURS to anneal cartridge brass.


You need to get to about that 625-650 degree number, more like 695 really, and get there quickly and reliably and prevent that heat from reaching the head (or even very far down the body) in order to do any good.

Frankly, I long since decided that it's just not worth it unless you're competing for titles or money. It's pointless for most people.... and potentially very dangerous.

[Ike666]

As to the "why bother" question - its a skill I don't have and want to learn. I want to see how it affects the whole operational process from brass prep through range time. If after a series of experiments it doesn't make any sense I can always discontinue.

I am reloading for accuracy and have a small collection of LC Match brass that I want to be able to use for a long time. For garden variety plinking I have about 2000 mixed LC cases, but I'm trying to see how tight I can bring the groups in and then how far I can shoot reliably - so, I'm looking to work up a loading recipe that will nip the cornea off of the proverbial gnat's eye.

I've watched the ammosmith video, and in fact that is the method that I'm using. Its pretty straight forward and works as demonstrated - but I haven't reloaded, fired and chronied any of the rounds processed in this fashion. I've got 25 of the LC Match I annealed this way and am planning a comparison shoot against some loaded with new Lapua brass.

Everything else (except for powder charge) will remain the same: 168 gn SIE HPBT, Fed 210M primers, and 4064 (I will run several different loads based on the favorite .308 load thread).

My real question here though has to do with the data on the materials website and the annealing temp. It takes about 8-9 seconds to get the color change in the brass recommended by ammmosmith, but I have no idea what the temp is actually running. They are run in a 12mm deep-well socket and the base and head are protected from direct heat exposure. It doesn't look like the high temp change goes more than a 1/3 of the way down the case. I dump them directly into a water bucket (room temp) and can pretty quickly retrieve them by the holding onto the head. While I'm all in favor of empiricism, I'd still like to know what the ideal annealing temp is and why the disparity between the materials website and what seems to be the more common practice amongst reloaders.

[mehavey]

Don't ever try to effectively anneal anything in an oven
- You don't get hot enough
- Whatever heat you do use softens the case head no less than the neck (bad juju)

The temp paste from Hornady says it is set at 475 F. This seems too low.

It is... deliberately. The 475 indicator fluid is put on the case at least a 1/4" below the shoulder. When directing the (high) heat directly at the neck as shown below, the neck is heated to much higher temps very quickly. The indicator fluid tells you when that heat starts creeping down/jacking up temperatures below the shoulder -- and when to quit.

[Unclenick]

Ike666,

The problem is that Matweb is giving you the actual annealing temperatures. What people do to extend the life of their brass is not actually annealing (at least, not on purpose), it is merely stress relieving, which happens at a lower temperature. Steel's the same way. It takes around 1550°F to anneal carbon steel, followed by slow cooling to keep it soft, but only about 1100°F to stress relive it. Annealing makes the brass soft and lowers it tensile strength by growing the grains, which you don't want in a cartridge case neck because it weakens the neck as well as its grip on the bullet.

You are correct the Tempilaq in the Hornady kit does not have a high enough temperature to indicate even stress relieving. Tempilaq of Tempilstik that is for a high enough temperature (650°F is commonly used) would be applied to the neck itself and watch for melting, then the neck quenched (to stop any grain growth that's started). The Hornady method is a little different. I haven't used it, but I read that they put that lower temperature indicator just below the shoulder, so the flame isn't directly on it, and as soon as it melts you know the neck was enough hotter to stress relieve and you don't want the heat to spread any further. I'm not sure why they picked that method over the usual one?

Brass Stress relief only requires 250°C-300°C (see chart below). The chart is for 1 hour exposure. Most folks use 650°F figuring to overshoot to 662°C, or 350°C, which does the job in the short time the flame is on without starting grain growth. It also puts you in a flatter part of the tensile strength curve, so your neck tension is more likely to be consistent.

[demigod]

As to the "why bother" question - its a skill I don't have and want to learn.

That's cool. You should have seen this video posted on ARFcom of some guy's automated system. It rotated the cases into the flame and kicked them out and everything. Very slick.

[Ike666]

Thanks Unclenick - those are the questions I wanted answered!


I saw that automated disc thingie - $450 nope, not me

[jmorris]

I saw that automated disc thingie - $450 nope, not me

I built mine, I have a lot of what my wife calls "junk" laying around but I have less than $100 in mine (not counting the case feeder off one of my 650's).



A video of how it works.

[F. Guffey]

Ike666, annealing is about heat, (TIME, TEMPERATURE AND TRAVEL), I make a tool for annealing, not for everyone and not for every case, it is about the amount of time invested on a case I put a lot of work into. I have no interest firing a case 55+ times, I do have an interest in forming cases I do not want to loose on the first firing because of splits the first time they are fired.

F. Guffey

[Ike666]

@jmorris - that's pretty slick; the double burner heats them up quick.

Is that an old circular saw blade you're using as a shell holder?

[jmorris]

Is that an old circular saw blade you're using as a shell holder?

No, it’s a part I have CNC laser cut from .125” steel, it will hold up to a 50 BMG. I sell a “blade” and scale traces of the top plate with hole location, torch arms and drive wheel for $60 shipped.

Step by step photos of the above build are here.
http://s121.photobucket.com/albums/o...etal/annealer/