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Old December 25, 2011, 08:40 PM   #26
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Jep2 you may very well be right about some of that brass. I based by comment on what I have worked with and when I weighed the cases to sort into uniform lots, they were all heavier than any commercial cases I have. I have not done the water test, just used the empty weight and assumed the common brass of equal weight would have nearly equal capacity. Obviously that can not be guaranteed.
My testing includes a chrony, which is, I think, a pretty good test of consistency of cases and loading technique. If 10 rd sample of a 100 rd lot give consistent velocity, I consider it pretty acceptable and have noticed that variable groups tend to coincide with amount of variation in velocity of samples.
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Old December 25, 2011, 11:11 PM   #27
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LC Brass sold as scrap = once fired brass.

Used brass is sold as scrap from the LC ammo plant. Some brass may have been used for this test.
The approximate shelf life of the ammunition is also tested here. "We place the ammunition in a chemical solution. This process allows for the brass imperfections to be easily identified" said Ojeda. "Any potential defects in the brass will become more apparent due to the reaction of the solution. Theoretically, the test makes it possible to identify flaws in the brass that under normal conditions, could only be noticed after a lengthy period of time."
The brass may have expanded in the web area to where it is not normally usable. Dealers will have this brass "roll sized" back to SAAMI standards, then its sold as once fired. This IMO can make the case head weak.
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Old December 26, 2011, 02:29 AM   #28
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Thanks to the OP for posting his question! I was going to ask about the best/quickest way to safely remove the crimp from Mill. brass and found my answer! Thanks guys!
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Old December 26, 2011, 02:30 PM   #29
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Brass capacity changes with brands, and sometimes within brands if the head design changes. That happened to Winchester .308 brass when they designed an extra light case to get more powder capacity for the 1992 Palma Match. They later adopted that design for all their brass, and today it is 35 grains lighter than some military 7.65×51 brass.

Since 70:30 cartridge brass has a specific gravity of 8.53 (from Matweb), each grain of difference in brass weight, if you assume the outside dimensions are constant, represents 0.117 grains difference in case water capacity. Difference in powder charge needed to reach the same peak pressure varies with the powder, but is normally somewhere between 50% and 75% of the water capacity difference under the bullet, so how much difference it makes in your case depends on how big a percentage of powder capacity that change is. For a .223 case 5 grains lighter than another, that's not quite 0.6 grains difference in water capacity and in most powders means you will use about 0.4 grains less powder in the heavier .223 case.

For .308 it's a bigger deal and can mean up to a couple of grains powder charge difference. The worst example is the .300 Win Mag, where the difference between the Remington an Norma cases can mean over 6 grains difference in powder charge. But for .223 it's not too bad.
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