Salt Bath Annealing, Pro's and Con's.

[Robinhood]

Case heads? Where did you get that? Necks and shoulders bruh.

[darkker]

Case heads? Where did you get that? Necks and shoulders bruh.

Re-read the write-up, mentioned specifically trying to and general methodology has three whole critter in the bath. Meaning the heads will be softened some amount.

[Robinhood]

Re-read the write-up, mentioned specifically trying to and general methodology has three whole critter in the bath. Meaning the heads will be softened some amount.

I have left brass in the bath for 5 minutes trying to soften the case head.

In the context of this quote, under the "pro's; paragraph 2" Tex was performing destructive testing by letting the brass heat soak with only the shoulders and neck in the bath for approximately 4 minutes 54 seconds longer than suggested time in the directions for a given temperature. This was an exercise to determine if the case head could be softened over a regulated amount of time. The results were much different than a flame from a propane torch that will destroy brass, size of the flame considered, at 5 minutes...or less.

So what did you get out of it?

[darkker]

So what did you get out of it?

I got that the whole case goes in a roughly 900 - 1,000 degree bath for 4-5 seconds for the process used to anneal. With that heat mass both inside and outside the case, the entire case will be annealed. Given the mass of the case head, it would likely be somewhat different than say the case mouth.
The temp for annealing(and tempilaq) cases is classically 750 degrees. It's pretty well agreed upon(right or wrong) that no part of a case should reach 950 deg during annealing as it will weaken the case. 800 deg at the case mouth takes only a few seconds to properly anneal. I'm concerned that 1,000-ish degrees inside and outside the case for 4-5 seconds will leave him with Federal-esque cases.

Federal brass(factory at least) is pretty well known to be soft, and many times too soft. It is great if you are selling factory ammo(use once and destroy), the case obturates extremely quickly and can contribute to the well earned reputation of "accurate" ammo; however not conducive to long life reloading. Prior to being able to test pressures I chocked it up to voodoo or over-pressure factory loads. Since then I've measured how little it takes to wreck some Federal brass; and subsequently, parts of your bolt-head. Measuring both extractor grooves, and case heads before and after measuring with the PT II; I've had "second firing" Federal loads expand and blow out the primers, extractors and etch bolt faces, needing a cleaning rod to hammer out the brass, at measured 50,000 PSI loadings.

Maybe I missed the vision, and certainly do what works for you, but be cautious about any possible softening of the case heads. Or at least keep spare parts handy.

Cheers

[Robinhood]

I've got you now. I agree on the 1000 degrees. The zink will start to liquefy below that I think very close to 900. I am not worried about heat soaking that fast but over annealing is a concern. The guys I know are somewhere around 800 to 850.


I don't think the process is flawed. One test is to weigh it before and after. If heat soak is a concern, What I did was put some 450 below the annealing line. If 750 is the "anneal" temp for C2600 brass and it never breaks 450 at the body above the head my belief is it is OK.Do you agree?

As always you have a keen eye for shortcomings.

[darkker]

I don't think the process is flawed. One test is to weigh it before and after. If heat soak is a concern, What I did was put some 450 below the annealing line. If 750 is the "anneal" temp for C2600 brass and it never breaks 450 at the body above the head my belief is it is OK.Do you agree?

As always you have a keen eye for shortcomings.

I don't think the fundamental process is any concern, no; only the temps being used.
I know that Lapua openly admits to using Olin alloy C260, everyone else seems to hold that in the realm of Super Secret Squirrel Sh....

As originally spec'd, C260 was a certain mix, with a tensile strength spec'd at 70-75,000psi. Which is another reason to not be to enamored with "signs" of case stretch for SAAMI MAP as reliable, but that's a side note. If someone else uses a different alloy, or tensile rating, it may not translate as well as hoped. But yes, 450 at the body wouldn't bother me personally either.

Cheers

[Savage170]

DARKKER:

"As originally spec'd, C260 was a certain mix, with a tensile strength spec'd at 70-75,000psi. ..... If someone else uses a different alloy, or tensile rating, it may not translate as well as hoped."


I analyzed some cases for my brother a few months ago, I thought Lapua was in here, it's not, but for what the info is worth here it is, I hope it contributes to the thread. This data is listed as MFG and Caliber, I do not know if the recipe translates across all calibers for a given MFG. This data is for a specific case, for a specific caliber, from a specific MFG.

Industry Brass 260 aka “Cartridge Brass”
Comments: Cartridge Brass
Copper, Cu 68.5 - 71.5 %
Zinc, Zn 28.5 - 31.5 %
Iron, Fe <= 0.050 %
Lead, Pb <= 0.070 %
Other, total <= 0.15 %

Federal 6.5 Creedmor
Comments: Brass 260
Copper 70.03%
Zinc 29.81%
Manganese .01%
Iron .05%
Tin .01%

Remington 280 Remington
Comments: Brass 260
Copper 71.55%
Zinc 28.25%
Aluminum .12%
Phosphorous .01%
Iron .04%
Tin .03%

Winchester .243 Win
Comments: Brass 260
Copper 69.99%
Zinc 29.52%
Aluminum .29%
Iron .06%
Nickle .03%
Tin .11%


Starline 7MM-08
Comments: 443
Copper 73.67%
Zinc 26.23%
Tin .04%
Iron .04%
Manganese .01%
Phosphorous .01%

[PhilC]

I got that the whole case goes in a roughly 900 - 1,000 degree bath for 4-5 seconds for the process used to anneal.

No it does not, only the neck/shoulder region goes in the solution. The case is set on a holder that limits how much of the neck/shoulder region can be immersed. Check the second linked video, this one, the guy is using his fingers to remove the brass and drop in his dunk bowl. No way he'd be doing that if the case head was 450° let alone 900°. Skip to 22:16 to bypass his wordy prelude and just watch the process.

At 23:58 you can see the depth line on the shoulder of the .223 case. He shows a clearer indication with some "dirty" 300WM brass at 25:28. Tempilaq on the case just above the holder would eliminate any question of overheating.

[darkker]

That's excellent, thank you for the link.

[Texas10]

Just to clarify a bit, the 3rd and 4th photos are of the baffle/case holder. The second of the two show the neck holder that suspends the brass to a fixed depth in the salt bath, which is adjusted to submerge only the portion you want. I prefer the salt to cover the neck and about half the shoulder.

The 1000 degree temp really does nothing to the composition of the brass in the short time it's heated. Annealing is dependent upon time at temperature, the hotter the temp, the faster the annealing process is completed. I found this process is actually faster then using a propane torch which burns at 3600*F (1980* C)
and unlikely to overheat the brass because it heats evenly inside and out.

If you like, you can google "salt bath annealing cartridge brass" to find some good video's, or go directly to the BallisticRecreations website link provided.

Good luck and good shooting.