Eric Cortina on annealing

[Rowboat]

Hi All, stumbled across a few YouTube vids by Eric Cortina describing his take on brass annealing. I think he enjoys controversy. He seems to be implying that annealing and particularly over annealing affects bullet grip or neck tension. Many seasoned shooters/reloaders would already be aware of this. I’m quite new to reloading and am also aware of the affect annealing has on rifle brass. My question is though, surely there are other consequences of over annealing brass other than perhaps a change in bullet grip or neck tension? As far as I am aware, once you have over annealed the brass or it has been overheated the composition of the brass has been disrupted. Just wondering what thoughts you all have on this.

[Tim L]

I'd agree with you and Eric does delve into this a little. His major concern seems to be that over annealing the neck could lead to annealing the body and even the case head. This is definately undesirable. I'm not at all sure on the change in composition, the brass was molten at some stage, but over cooking it does leave the neck unsuitable for use.
He has done a video of the effects of neck tension on over annealed brass using the force gauges on a K&M. The results are pretty much what you'd expect.

[Wingnut]

The application of heat adjusts the molecular distribution within the brass. Effectively it softens it. This can allow the brass to react differently when the shot is fired, possibly flowing into areas where you don’t want it to and stretching in other regions, some times catastrophically. Of interest is the fact the new Bi-metal cartridges under development for the US army’s new rifle system are able to withstand pressures of around 80k psi. The key area is the lower portion of the case which is not enclosed within the chamber and requires the strength of the metal to prevent the case rupturing.

[Rowboat]

I know what you mean in regard to annealing too far down the case and he did actually mention this. What I found interesting was that he concluded that the window between properly annealed and slightly over annealed was bigger than you might think. This is not what I have been told or experienced. It will also be interesting to see the results of his comparison between a bench source annealer and an AMP. And, if that equates to better results on target.

[Gyro]

Realize too Rowboat that it's very hard to prove the 'efficacy' (usefulness) of lots of stuff in this game and annealing is very much in that basket.

[Tim L]

I know what you mean in regard to annealing too far down the case and he did actually mention this. What I found interesting was that he concluded that the window between properly annealed and slightly over annealed was bigger than you might think. This is not what I have been told or experienced. It will also be interesting to see the results of his comparison between a bench source annealer and an AMP. And, if that equates to better results on target.

Rather than going into a huge monologue here the AMP page contains a huge wealth of information specific to annealing brass cases. Yes, they are trying to sell a product, but much of the info is simple, fact based from studies and testing.
More recently they have been delving into the effects of annealing, take that info as you will.

The important thing to remember is brass is an alloy, supposedly 70/30 copper/zinc, but we really don't know what percentages or imputities our particular batch of cases contain. Impurities, in particular, effect the annealing temp. Figures range from 350 to 800 c, with brass melting at just over 900c.
My take is that the process starts at the lower temp, but takes longer. At the upper end it's all but instant. Just above the upper end and it's buggered! Middle for diddle (just starting to glow) every firing will impart "some" benefit and does, at least as far as I can tell, stop the necks hardening and gives what I perceive as consistant seating.
In my process it also ensures the brass is dry

[Tim L]

It will also be interesting to see the results of his comparison between a bench source annealer and an AMP. And, if that equates to better results on target.

Spoiler alert
He's going to find no difference.
The AMP is just easier to use, and safer given there's no flame.

[bruce moulds]

tim l
good post.
bruce.

[tachyon]

The Internet is awash with opinions about annealing. Here are a few observations:

1) It is almost impossible to over anneal a brass case with a propane torch
2) Annealing may REDUCE your ammo consistency if you do not anneal consistently
3) You do not need to anneal to get a low ES/SD but it may assist...

[pjifl]

It is almost impossible to over anneal a brass case with a propane torch

I am not too sure about that. Oxidation of the Zn component of the allow can happen - depending somewhat on time of exposure.

For some reason, Shooters seem to think the Metallurgy of annealing Brass and Bronze and their alloys has some secrets.

Annealing and Heat treating of metals and their allows has been studied in depth for a long long time. The only difficulty comes from applying it selectively and uniformly to the top portion of the case with crude equipment.

If you do research on this and associated metallurgy, first of all realize that Cartridge Cases are not 'Brass'. They are more akin to Bronze alloys or Gunmetal than simple Brass.

Peter Smith.

[Tim L]

The Internet is awash with opinions about annealing. Here are a few observations:

1) It is almost impossible to over anneal a brass case with a propane torch
2) Annealing may REDUCE your ammo consistency if you do not anneal consistently
3) You do not need to anneal to get a low ES/SD but it may assist...

That first one, yeah, nah.
It is very easy to over anneal brass with propane. I made my own propane annealer before buying an AMP. Propane can cook the neck, anneal the whole case as well as melt it. I've done all 3.
The other two are fair enough.

[tachyon]

If you do research on this and associated metallurgy, first of all realize that Cartridge Cases are not 'Brass'. They are more akin to Bronze alloys or Gunmetal than simple Brass.

Gunmetal has a significant quantity of tin and is roughly 88% copper, 10% tin and 2% zinc

Bronze has lots of recipes but is ~86% copper, ~ 12% tin, and a little bit of aluminium, manganese, nickel or zinc

Brass is an almost pure Copper/Zinc alloy

This Xray spectrometer testing from Accurateshooter demonstrates cartridge cases are definitely brass http://bulletin.accurateshooter.com/201 ... ctrometers

[pjifl]

The essential thing about cartridge 'brass' is that it has a higher proportion of Copper than common Brass. The table in the article (above) referred to bears this out. Cartridge brass is usually in the 70 - 80 percent range. I have seen previously published analysis of Lapua or Norma (not sure now which) which also contained a few % of Tin.

The article mentions surprise at some Lapua PPC which supposedly contained 62 Cu and 32 Tin. If this is true, I am amazed and would like to see this confirmed.

Many Metalurgists class the Alloys between Bronze and Brass with high Cu content as red brasses to distinguish them from common Brass.

While traditional Bronze contains a high portion of Tin, it can be much lower than 12%.

The essential feature of Gunmetal is a high Cu content. The percent of Tin can be lower. The original makers of Gunmetal Cannon and Boat fittings liked the Tin content to be high plus a trace of Zn because it tended to cast with fewer flaws. Also stronger than common Brass and quite corrosion resistant. Gunmetal is often classed with the Red Brasses. The 12% Tin casts well into molds often with a few percent Zn. A common alloy today contains only 5 % Cu plus some Zn. This is not normally cast into molds - the continuous casting method has made this alloy possible.

Depending on composition, different crystal compositions predominate over a temperature range. Metallurgists tend to classify the alloy by the crystal content called Alpha Type. This predominates in the lower Cu brasses but the higher % alloys are different. Museums and Retailers tend to classify by colour.

It was probably quite unwise of me to make the sweeping statements about Brass, Bronze and Gunmetal. But I definitely contend that you can overheat cartridge brass with a propane torch.

Peter Smith.

[6.5x55ai]

And overheating he was. If you watch his first video he was using just over 6 seconds on the Bench Source, and was getting a cheery red glow in the neck and shoulder region. At around 5 seconds there was a lot of sparkling red colour above the cartridge indicating elements within the alloy were burning off. He was also adjusting the flames closer than recommended with the hotest part of the flames right up to the neck.

When I was using a Bench Source with similar catridges I got satisfactory annealing (confirmed with Omegalac) @3.25 to 3.75 seconds. And that was with std gas not MAP.

He must of got a bit of stick after the first vid (he did sorta mention it in the 2nd) because he finally pointed out the risk of over cooking the base.

And b4 I again get accused of being a keyboard warrior like I was once b4 when I made a comment on Erik, yes he did finish in the top 10 at the recent US National's so who am I to point out these things about his method.
He's obviously doing most things right plus it brings into question how important is accurate annealing.

BTW Nowadays I am in the annealing after every firing camp.

[Rowboat]

I also agree that you can over anneal with a flame torch. However, getting back to Erik's comment on the window between annealed and over annealed as ranging between 6 and 10 seconds. Meaning using his equipment after 10 seconds the cases are toast or over baked That's a big window given that as far as I know this is a pretty precise process. I think he may have over simplified this topic a little. He does like to stir the pot though. BTW I'd buy an AMP annealer tomorrow if my wife would let me.