More Zinc in the brass?

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exbrit49

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Hi Guys, do we have any metalurgists here that can confirm the brass alloy W-W is using?
I have been reloading for more years than I want to count and I was really surprised to notice that my latest batches of W-W Long colt brass doesnt polish up nearly as well as the old stuff I have.
The newer brass is whiter in appearance than the older stuff, and it wont produce the really bright shine I get when tumbling the old brass. It just wont produce that beautiful golden sheen that the older stuff has. It really does have a much different apperance.
My suspicion is that as the price of copper has increased, Winchester and several other manufacturers have increased the zinc content. The usual alloy for cartridge cases should be 70% copper, 30% zinc. Judging from the color and behaviour of the new brass, I would guess that the zinc content is much higher.
If indeed the alloy has changed, then I suspect we will see much shorter case life.
I have many cases that have been loaded more than 20 times with moderate loads. I dont think the new brass is going to last as long!
Roger
 
The range of Copper/Zinc ratios suitable for use in cartridges intended for reloading is 80/20 to 70/30. Above 80% copper, the resulting case would tend to be too soft and difficult to attain the distribution of hardness desired (harder at the base and softer at the neck). Below 70% copper the resulting case would tend to be too hard, would work harden too quickly and require frequent annealing. [Editor: That said, the 'brown box' 6mmBR Lapua brass, with 62% copper/36% zinc content, enjoys an unrivaled reputation for both accuracy and its ability to perform well after a dozen or more reloading cycles. We know 30BR shooters who have shot the same old-style Lapua brass (6mmBR parent case) more than 50 times. So maybe the "expert" view needs re-thinking.]
Click to expand...

http://bulletin.accurateshooter.com/2011/09/cartridge-brass-alloys-revealed-by-x-ray-spectrometers/

BR chamber are often cut very 'tight' at the bottom end of allowable chamber size.

This means the brass is not worked nearly as much during repeated sizing and fringe.

I have tight neck chambers that I barely have 0.0015 of clearance to a loaded and turned case.

Some cases have lasted over 30 shots at very high pressure.

A shoulder bump is only required after about 15 cycles.
other than that, minimal neck sizing to get about .002o of neck tension.
 
Thanks for the responses, especially the article posted by bfoosh, It explains a lot. From the article it would appear that the higher zinc in the Winchester should not significantly affect case life.
I will track these recent batches and see how the life compares to my older brass. The article shows the R-P at 80% Copper and my own observation would agree that a much better shine is attainable from tumbling/polishing thse.
The much lower percentage copper in the W-W is visible from a color standpoint and general appearance.
Great articles and good reading!
Thanks again to all
Roger
 
Foosh for the win !

I will add, that with newer winchester brass offering ( win is my fav brass )I've been able to obtain a deeper lustre, but a less golden, shine. It also oxidizes slower when exposed to air.


I have a new load of them for both 45 ACP, and .30-30I'm going to do my best to wear out this summer....I'll keep everyone posted.

my $0.02.
 
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