Brass Variabilty

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Macd
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Brass Variabilty

Post by Macd »

I am not telling anyone something new when I say that all brass is not made the same or that it changes over time. Like many I have cases that are brand new, over 50 years old, fired and sized from 1 to 20 times and from many manufacturers of cartridges. Of course some ammo makers buy their brass from others and it may be differ depending on supplier. Some have been annealed once and others several times. Some are neck sized most of the time and others are full length sized all of the time. Some have been fire or cold formed or both from another calibre. While conventional wisdom says that my mil surplus brass is thicker I have found commercial brass that is heavier when case weights are compared. I don't have the equipment to measure brass chemical composition but the accepted 70/30% copper/zinc ratio is apparently not necessarily what you get. Read this article for more information.

http://bulletin.accurateshooter.com/201 ... trometers/

All this to say that I find this variation very interesting and have experienced its effect on reloading in a number of ways.
- Case stretch
- Bullet grip
- case splitting
- Primer pocket loosening
- Bullet seating resistance
- resistance or affinity to cold and fire forming
The discussion on Starline brass problems experienced by some here reawakened my interest in this subject. Why are people experiencing case failures that point to brittle brass? I haven't experienced any case failures problems but I only use their brass for 45 Colt. I have had some minor issue with bullet grip. Is it something in their manufacturing process or the chemical composition of the brass? Some of my 45 Colt brass is put aside for annealing. It will be interesting to see how these compare to new cases.

Edited to correct ratio in the first paragraph of copper to zinc in C26000 Cartridge Brass.
Last edited by Macd on 27 Apr 2019 18:16, edited 2 times in total.
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Re: Brass Variabilty

Post by RBHarter »

I had a tried and true load for a 45 Colts that got better with neck sizing . The Winchester brass at 17-18 cycles started smoking cases so I played with the load and other such . About 25 cycles I annealed them and the smoking stopped . I have to figure that the cases had reached the work hardened point where 21-23 kpsi wouldn't seal any more . In a Ruger .
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Re: Brass Variabilty

Post by Macd »

I am on a quest to understand why brass varies so much between makers and perhaps lots from the same maker. The anecdotal reports on the forums don't add much but some are interesting. The first step was to understand the composition of cartridge brass. In my first post I gave a link to an article that addressed this in a technically objective manner. I have since gone on to how cases are made. Here is a good explanation on the process.
https://www.petersoncartridge.com/our-d ... ing-brass/
My next leg of the journey will be to try to understand the reasons brass fails from a metallurgical approach.
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Re: Brass Variabilty

Post by Macd »

http://bulletin.accurateshooter.com/201 ... hs-busted/

Another good read especially the full reports.
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Re: Brass Variabilty

Post by Macd »

Season or stress cracking. This is an excellent summary.

http://hghouston.com/resources/material ... c-cracking

Note that the higher the concentration of zinc in brass the more susceptible to cracking. High zinc brass also work hardens faster and requires more time to anneal. This may introduce or leave the stresses needed for cracking to occur.

I am getting close to the end of my research on why brass (cartridge cases) vary so much. I will post a brief summary when done if anyone is interested. As usual it comes down to, IMHO, the cost of the feedstock and manufacturing processes in making the cases. Quality cartridge cases cost more to produce. Saving only cents per case when you are making millions of cases really adds up. High demand creates pressure to reduce manufacturing time. Low demand puts competitive pressure on to lower costs. I have a nephew who is a Sigma Six qualified consultant. He once told me the ultimate objective of any manufacturing process is not necessarily to prevent all failures but to reach a goal of the most profitable rate of failures.
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Re: Brass Variabilty

Post by Ohio3Wheels »

As far as I know Winchester is the only ammunition manufacturer that maintains complete control over the process from raw brass stock to completed rounds. Olin metals makes the brass feed stock that goes into the cases and as far as I know the cases are all drawn in East Alton. Back in the late 50s and early 60s my Dad worked for Olin Metals so I had some first hand experience with Olin.

My current hand loading seems to largely involve the 38-55. I have one batch of 50 Starline cases and 150 same lot Winchester cases. So far the SL and one group of 50 Winchester are on their third loading. Keeping track to see what their life will be like.

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Curt.......makin' smoke and raising my carbon foot print one cartridge at a time +guns +guns
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Re: Brass Variabilty

Post by Ranch Dog »

Winchester is my favorite.
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