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Over annealing cartridge brass

 
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Old 10-07-2013, 12:16 PM
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Over annealing cartridge brass

I read in an article on 6mm br about annealing that stated if you heat your necks beyond a faint glow of orange ( 950 deg F ) that it will fully anneal the brass removing some of the hardness inflicted by the manufacturing process and will then not provide sufficient neck tension.

I was under the impression the point of annealing case neck was to return them to the brass's original state. Can someone straighten me out please?

The Art and Science of Annealing
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  #2  
Old 10-07-2013, 01:31 PM
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Re: Over annealing cartridge brass

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Originally Posted by Canadian Bushman View Post
I was under the impression the point of annealing case neck was to return them to the brass's original state. Can someone straighten me out please?

The Art and Science of Annealing
Correct. Over annealing is annealing more of the brass than the neck and shoulder area. If you anneal the entire brass it will fail under pressure. If you keep too much time on the tourch(s) heating the neck and shoulder you will start to anneal the body of the brass. Not good and dangerous.

Read this post. I hope this answers your question. problem with tempilaq
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Old 10-07-2013, 03:17 PM
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Re: Over annealing cartridge brass

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Originally Posted by MMERSS View Post
Correct. Over annealing is annealing more of the brass than the neck and shoulder area. If you anneal the entire brass it will fail under pressure. If you keep too much time on the tourch(s) heating the neck and shoulder you will start to anneal the body of the brass. Not good and dangerous.

Read this post. I hope this answers your question. problem with tempilaq
I do understand this. That makes sense.

I was referring to the part where talks about over annealing the neck resulting in too little neck tension


To quote the author
Quote:
The trick is to heat the neck just to the point where the grain structure becomes sufficiently large enough to give the case a springy property, leaving the body changed but little, and the head of the case virtually unchanged.

If cases are heated to about 600 degrees (F) for one hour, they will be thoroughly annealed--head and body included. That is, they will be ruined. (For a temperature comparison, pure lead melts at 621.3 degrees F).

The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees (F) for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft.
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Old 10-07-2013, 08:22 PM
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Re: Over annealing cartridge brass

I can say this. I left my annealing machine on for 15 seconds on an old 308 brass. After cooling I pressed the neck on the table and with little effort the neck bent. The brass was very soft. I didn't try work hardening but this confirmed over heating and too much time will soften the brass to unusable parameters.
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Old 10-07-2013, 08:35 PM
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Re: Over annealing cartridge brass

Thats about the idea that was conveyed to me through the article i posted.
Did you ever try shooting one next to one or a few that you annealed normally to see what changes may occur?
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Old 10-07-2013, 08:38 PM
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Re: Over annealing cartridge brass

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Originally Posted by Canadian Bushman View Post
Thats about the idea that was conveyed to me through the article i posted.
Did you ever try shooting one next to one or a few that you annealed normally to see what changes may occur?
Without work hardening no way! I want to live to this hunting season.
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Old 10-07-2013, 09:16 PM
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Re: Over annealing cartridge brass

I did a test to prove to myself what would happen if NECKS were "over annealed"

I heated neck and shoulders of 308 lapua brass to a point of an 8 second long, mid-to bright orange glow. While doing this the case body and heads were protected from the heat to insure we did not create a dangerous situation with softened case bodies. Assisting me was a national level f-class shooter who owns an annealing machine, and declared the brass we just annealed was surely ruined.

I loaded the brass with the same load that I used previously, and fired a 5 shot sub 1/2moa group at 100 yards. yes the neck tension was lighter, by feel of seating bullets, than it had been previous to the "over annealing" but non the less they held the bullets with-out slipping and the accuracy was unchanged.

If you think you annealed the body of your brass throw it away, if you think you over annealed the necks you just might shoot the brass before you pass judgement.
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