Random annealing question

[TheGerman]

I never tumbled brass after shooting it prior to annealing unless it was nasty for some reason. Otherwise I'd decap, anneal, lube, size, trim and then toss it in the tumbler to primarily get the lube off.

On the instructions for the AMP, they state you should tumble once after decapping prior to annealing, which would then make me tumble the same brass twice, as I'd tumble again after sizing. Is this just them being extra anal about this, or is there a reason/benefit/need to tumbeling before annealing? I would prefer to not do anything that isn't needed because tumbeling a second time adds a shit load of time to my reloading process.

I was also curious about something in regards to having the same brass, fired from the same gun yet had a different number of firings on it (within 1 or 2 of each other) and if annealing 'fixes' any differences in them? For example, I have Hornady 6.5CM brass I bought a ton of. Over time I have different lots of the Hornady brass separated by firings, yet all from the same gun and no other permanent 'adjustments' made to the brass (i.e. not neck turned).

If I took all of the once fired brass and annealed it as well as took the twice or three times fired brass and annealed them the exact same way, would the brass as far as the next loading be identical/'fixed' or are there still differences in the brass that would be detrimental to accuracy and/or keeping low ES/SD, etc?

 

[Precision Underground]

I like to clean before annealing because it is easier to read the brass when timing my machine. When it is dirty you can get funky reactions from the flame that make it hard to tell what is happening heat-wise.

 

[918v]

Final brass hardness depends on temperature and time. Logic would dictate that if you start off with two cases, one harder than the other, and you anneal them using the same temperature and time, then you should end up with two different hardnesses.

 

[Snuby642]

I may be stupid but was under an assumption that annealed was the same no matter the starting point.
As in annealed to soft is just that. Not dependant on previous firings?
Please set me strait.

We would take different metals anneal them and then have them hardened
to one common state, as I remember it?

 

[Sean the Nailer]

Final brass hardness depends on temperature and time. Logic would dictate that if you start off with two cases, one harder than the other, and you anneal them using the same temperature and time, then you should end up with two different hardnesses.

I've been wrong before, but I disagree with this statement.
If using flame or electric (the AMP is electric if I recall correctly) once the material gets up to the critical temperature, then the critical temperature has been met. Therefore, the molecular structure of the metal HAS reached the point of it's anneal. Done and done.

Now, if we were to be talking about heat-treating alloyed steel for the purpose of hardening, or toughening, then THAT is a whole different topic.

 

[Snuby642]

Had some weird stuff over the years.
Soft "annealed" aluminum, work / form it, coald soak it, and rework it
To final shape before it came to room temp.

 

[918v]

I've been wrong before, but I disagree with this statement.
If using flame or electric (the AMP is electric if I recall correctly) once the material gets up to the critical temperature, then the critical temperature has been met. Therefore, the molecular structure of the metal HAS reached the point of it's anneal. Done and done.

Now, if we were to be talking about heat-treating alloyed steel for the purpose of hardening, or toughening, then THAT is a whole different topic.

But the critical temperature you’re thinking of is way too high. We work with semi-hardened brass that has elastic properties which enable it to retain the bullet.

 

[Snuby642]

So the brass works different than steel or aluminum?
Ok never had any to heat treat.
With the steel and aluminum in annealed state it had nearly zero
Elasticity "spring back" so misakenly figured brass similar.

 

[918v]

Cartridge brass has/needs springback otherwise the neck would not be able to hold the bullet. When we anneal our brass we are softening it but not to the point where it is dead soft. I have found 650 degrees F to be ideal. The necks will never split but they have plenty of spring to them.

 

[MarinePMI]

@TheGerman , I believe they recommend this because they expect you to anneal indoors, and if the cases are dirty, there will be a burning off of the residue in the case.