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Old February 24, 2013, 08:24 PM   #1
ScottRiqui
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Is most cartridge brass pretty much the same stuff?

Does anyone here know offhand if the brass used for most ammunition is pretty similar from a metallurgical point of view? Specifically, I'm wondering about the density.
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Old February 24, 2013, 08:36 PM   #2
Slamfire
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The composition of 70/30 brass is pretty much the same for all cartridge brass.

Density, M/V, I really doubt it will vary by much. The stuff comes to the cartridge factory on rolls.

What will be different is cartridge weight, that is how much brass is in the case because cases have different sidewall and case head thickness. Varies a little bit.

What also will be different is the hardness. The case is of different hardness from base to mouth. But depending on the annealing processes, brass can be a little harder.

I read that LC wanted quarter hard brass. Obviously the case neck was annealed.

This site has differences in strength and ductility between quarter hard, half hard, etc.

http://www.lfa-wire.com/70-30-Brass-Wire_C26000.htm
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Old February 24, 2013, 08:38 PM   #3
oryx
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just beat me to it...
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Old February 24, 2013, 09:00 PM   #4
ScottRiqui
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Thanks. This may sound silly, but here's the reason for the question:

I'm waiting on delivery of one of the "Stainless Tumbling Media" kits, and the directions say to use five pounds of pins, one gallon of water, and two pounds of brass. I know those numbers aren't critical, but I like to be as close as I can on recipes if it's not too difficult.

My plan was to dump the pins in the tumbler, measure out a gallon of water, and pour it in the tumbler. Then I'd mark the water level on the inner tumbler liner with a scribe or some other permanent method. Then, I'd weigh out two pounds of brass and dump it in as well, marking the new water level.

Then in the future, all I'd have to do is put the pins in the tumbler, add water until the water level hits the lower scribe mark, and then add brass until the water level hits the higher scribe mark. Obviously, this would only work if the density of the brass was pretty much constant across calibers/brands.
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Old February 24, 2013, 09:21 PM   #5
david_r
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whatcha gonna do when there are air pockets in the cases? It would be easier for you to make yourself a scoop for each caliber that is about a pound of brass. I would suggest that at 6.5 inches diameter, the water level in your tumbler would change about 1/10" per pound of brass. That seems a little difficult to measure. If you want to cut it so fine, get a postal scale and weigh it as you fill it.
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Old February 24, 2013, 09:45 PM   #6
ScottRiqui
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Thanks for that - I didn't realize that the two scribe marks would be so close together, but I ran the numbers and got the same result you did.

I wasn't worried about air pockets, since the cases will be deprimed, and as long as I added them a handful at a time, they'd orient themselves "head down/mouth up" pretty quickly as they fell through the water.

But I do have an electronic scale that lives in the kitchen where I'll be doing the tumbling, so it won't be too much extra work to use that. I'll still scribe a line for the water level though, so I can just stick the tumbler barrel under the tap to fill it.
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Old February 24, 2013, 10:31 PM   #7
rg1
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Here's a good article:
http://bulletin.accurateshooter.com/...spectrometers/
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Old February 24, 2013, 11:21 PM   #8
david_r
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I knew I read that article somewhere recently. There are a number of good articles over there
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Old February 25, 2013, 02:08 AM   #9
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Beat me to it.

Note that in that article, only two of the seven samples tested even qualified as 'Cartridge Brass'. Four were 'Low Brass', and one lot had enough zinc to qualify as 'Muntz Metal'.

"Cartridge Brass" is nowhere near as uniform as most people believe. Some manufacturers use substantially different alloys for different cartridges.
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Old February 25, 2013, 06:23 AM   #10
hooligan1
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Slamfire, some of the different cases Lake City makes using copper slugs, then they are hammered to different sizes and shapes, a friend showed me the process, about four steps, I think.
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Old February 25, 2013, 10:12 AM   #11
BoogieMan
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Just to through something a little diferent into the mix. I shoot a lot of PMC Bronze. Not sure if that refers to the bullet or the case. But they did shine up much better than the Aquila or other brand cases that I ran through the tumbler.
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