Salt Bath Annealing Doesn't Work! by AMP

[Rick Richard]

From the man himself:

Thanks for reaching out to me. I knew that the folks at AMP were doing some lab tests with the salt bath process but I wasn't expecting such a hack job with the reporting.

I've just had a chance to read it through once, and my first reaction is a little jealousy that they have the ability to do all this lab work that I've always wanted to do, but don't have the resources for. Next comes a feeling of irritation that for the last two years the number one criticism I've faced is the accusation that even the bottom end of my range (450°C) was too hot (from all the people who took the internet-accepted number of 750°F as gospel), now I'm reading an attack that says even my top end of 550° is too cold! Call it proof that you just can't make everyone happy.

I will take some time to read it carefully and formulate a response.
Regards,

Gary Chambers
Ballistic Recreations
Edmonton, Alberta, Canada

 

[Deputy819]

His response to me as well:

Hi, thanks for the heads up, I knew the folks at AMP were
preparing some lab tests on my process, but I didn't suspect it was
going to be such a vicious attack. I will have to look closely at it
and think on the results.

Regards,

Gary Chambers
Ballistic Recreations
Edmonton, Alberta, Canada

 

[Barrelnut]

My question is why salt bath annealing seems to be annealing the shoulder area MORE than the neck. It is easily visible in the graphs. AMP does not discern the reason for this phenomenon. Is it because the temp is not consistent through out the depth of the molten salts? Almost seems the salts the neck portion of the cartridge is submerged in, is not heated a much as the shoulder which is submerged much higher in the salts. Heat rises. Also the shoulder this thicker than the neck, so all being equal, seems the neck would heat quicker and anneal quicker.

 

[ar10ar15man]

yeah but.
i saw potential issue with brian's test
it does not fir my data either.
i load different than he does.
my expectations are higher.
lots of good stuff from his work, does
not mean it fits all shooting styles/types.
we are comparing TWO TYPES OF ANNEALING, not to anneal or not.

Well another simple test is to shoot bullets from the same cases. 10 times.
One set of cases anneal every firing.
One set anneal every other firing.
One set anneal at the beginning and after the fifth firing.
And one set anneal only at the beginning.
Compare chronograph data from the sets and targets.

It has been done. Check Bryan Litz's work.

 

[ar10ar15man]

SIMPLE ANSWER.
THE MIL DOES NOT RELOAD.

If I recall a Rockwell hardness test from Catshooter, Lake City 5.56 was the hardest of any case tested. What's good for military might not be good for our purposes.
As JE says, it's just info, make your own conclusion on what to do with it.

Edit; it does seem strange how a neck could not be annealed but the shoulder over annealed.

 

[Wedgy]

SIMPLE ANSWER.
THE MIL DOES NOT RELOAD.

OR... what's good in a barrel melting machine gun isn't good for my purposes

 

[86alaskan]

It's all kinda hocus pocus, some see results, other do not. some swear you can't shoot well without it, others win without it. I've seen tests with a sample lot, run multiple firings without, with and with different stages of annealing, and the ES/SD #'s varied across all testes. Nothing consistent enough to track. Hell, one test showed smaller groups and ES/SD with brass that was 5x fired with no annealing rather than the lot that was perfectly annealed every time. I've just begun salt bath, and the seating feels more consistent. I'll keep trying it, until I get bored with it or it shows results one way or another.

 

[Mikecr]

There is other potential trickery here. I don't understand how they managed such a jump in hardness from baseline with cases reloaded 2-3 times. That would take a helluvalot of work hardening. In such a case, full annealing may actually be in order to recover. That is, way more softening than normally needed.

See, I don't want my brass to be soft anywhere. My standard for annealing is not to make it soft, but to relieve stress, managing what I load developed at. Of course it's easier to just prevent work hardening as I go, only annealing now & then as needed.

Salt dipping is not for full annealing. So I'm thinking this testing creeped out of the basic function of dip annealing. They baked cases in a salt bath -that was below temperature needed for full annealing, which is not what I wish to do with dipping anyway, and then criticized the method for not fully recovering wildy work hardened cases..
Trying not to be defensive here, but I do know that dip annealing works great for me.

 

[J E Custom]

More information !!!

http://www.metalmart.com/tools/hardness-conversions/brass/

No doubt that different cartridges need different hardness's for their use. and most re loaders would probably want the case to be on the soft side (MINIMUM), but resizing some cases to soft can lead to other problems.

J E CUSTOM

 

[tailbon3]

Seems to me that AMP's testing implies a possible solution, if there really is a problem to begin with. I'd like to see the results if the case was lowered into the salt bath so just the neck was submerged for 4 seconds, then the case was lowered to cover just above the shoulder for the remaining 4 seconds. Seems like that would give the neck more time to anneal and the shoulder less time to over-soften. I agree with the previous post by BarrelNut that the hottest salt must be rising to the top which leads to over annealing the case body. A two-step dip may well mitigate that problem. The assumption by AMP that salt-bath annealing CAN'T work just because their tests didn't work, seems fishy to me. I think that might be the very definition of bias

 

[Wedgy]

I'd like to see the results if the case was lowered into the salt bath so just the neck was submerged for 4 seconds, then the case was lowered to cover just above the shoulder for the remaining 4 seconds. Seems like that would give the neck more time to anneal and the shoulder less time to over-soften. I agree with the previous post by BarrelNut that the hottest salt must be rising to the top which leads to over annealing the case body. A two-step dip may well mitigate that problem. The assumption by AMP that salt-bath annealing CAN'T work just because their tests didn't work, seems fishy to me. I think that might be the very definition of bias

That would explain their results of uneven annealing and offer a solution....
1) stir the bath
2) two stage dip

They might have to thank AMP for pointing that out

 

[kiwikid]

Reading through the posts I noticed that brian b, Mikecr, Kyron and possibly others suggested that AMP have done this testing because the Salt Bath Annealing has put a dent in their sales.
If this were true why would AMP have suggested this in the second to last paragraph of their report,
"For those reloaders considering getting started on annealing, and who are on a budget, we would recommend a gas flame-based option." ?

 

[J E Custom]

My question is why salt bath annealing seems to be annealing the shoulder area MORE than the neck. It is easily visible in the graphs. AMP does not discern the reason for this phenomenon. Is it because the temp is not consistent through out the depth of the molten salts? Almost seems the salts the neck portion of the cartridge is submerged in, is not heated a much as the shoulder which is submerged much higher in the salts. Heat rises. Also the shoulder this thicker than the neck, so all being equal, seems the neck would heat quicker and anneal quicker.

I only have a theory as to how. We know if we over heat the case mouth, we not only ruin it but change the allow content by burning one of the alloys off. this could definitely effect the hardness where it is over heated.I did catch an error in my interpretation of the post that I posted. I though the recommended temperature was in Fahrenheit and the reason I thought it was to low and I saw where the manufacture said it was Celsius. (Big difference, My Bad) 750 f is almost exactly 400 c

J E CUSTOM

 

[Dr. Vette]

I though the recommended temperature was in Fahrenheit and the reason I thought it was to low and I saw where the manufacture said it was Celsius. (Big difference, My Bad) 750 c is almost exactly 400 f.

J E CUSTOM

Other way around.

400C is about 750F. (752)