checking volume of brass

phorwath said:

The volume of a unit weight of water, no matter which unit of weight measure used, is more than 8 times greater than the same weight of brass case material. It simply means the volume of water you're able to repeatably, accurately measure by weight, is 8x greater than the volume of case brass you'll be able to accurately measure by weight, with whatever scale you use to measure the weight.

I suppose the crux of the matter is; ... does one believe the exterior dimensions of a quality brand of brass casings, after fire-formed to your chamber, possesses exterior dimensional tolerances so poor that you'll get better inner case volume comparisons by weighing the volume of water in the case, rather than by weighing the brass case material itself. Knowing that volumetric differences in brass are much more easily detected, and that increasing brass case weight means less inner case volume.

If the cases were manufactured by Jed Clampett, or you're mixing multiple brands of cases while at the same time in pursuit of identical inner case volumes, well perhaps the answer is yes. Then it might be preferable to fill each case with liquid and then weigh the liquid weight. Or make life simpler. Discard the Jed Clampett head-stamped cartridge casings.

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phorwath said:

The volume of a unit weight of water, no matter which unit of weight measure used, is more than 8 times greater than the same weight of brass case material. It simply means the volume of water you're able to repeatably, accurately measure by weight, is 8x greater than the volume of case brass you'll be able to accurately measure by weight, with whatever scale you use to measure the weight.

I suppose the crux of the matter is; ... does one believe the exterior dimensions of a quality brand of brass casings, after fire-formed to your chamber, possesses exterior dimensional tolerances so poor that you'll get better inner case volume comparisons by weighing the volume of water in the case, rather than by weighing the brass case material itself. Knowing that volumetric differences in brass are much more easily detected, and that increasing brass case weight means less inner case volume.

If the cases were manufactured by Jed Clampett, or you're mixing multiple brands of cases while at the same time in pursuit of identical inner case volumes, well perhaps the answer is yes. Then it might be preferable to fill each case with liquid and then weigh the liquid weight. Or make life simpler. Discard the Jed Clampett head-stamped cartridge casings.

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Steve Sheasly said:

It is important to me to separate my once fired brass not by manufacturer or by weight (you can assume that I have done everything to the brass to make it uniform, concentric etc..) but by volume. assuming the case is in good shape and not abused volume is the only thing that will affect the accuracy. Weight is not volume and has zero effect on the powder burn characteristics threfore pressures. So lets just look at measuring volume.

I am using alcohol over live primers to measure volume. I have a methodology that has given me 100 percent repeatability for any specific case measured. My question is has anyone fired a primer that has been soaked in 70% isopropyl alcohol (yes I realize the other 30 percent is water) I did not have any 200 proof alcohol, I am awaiting an answer from CCI to see if this will damage their primers or not and for what type of non viscus liquid will work. I know this is a bit unOrthodox but if I can get repeatable volumes this way and the primers are not hurt it will keep me from having to machine a precision primer plug. I do not like the ones on the market besides it changes the volume (just a hair but it does change it) the primer used to fire the cartridge will be the saem on in the volume calc.

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antelopedundee said:

Just curious if you dry the primed cases after filling with alcohol or use them wet? If you dry them how do you dry them. If you fill them with powder while still wet how do they fire after sitting around for a month?

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Steve Sheasly said:

this is what I was told. Having worked with foundry's and with extrusion processes for decades I know that tolerances are very good but not perfect. The head of the case holds the most weight of the case and is also where the most variability is.
s The inconsistency of this one variable is enough for me to justify volume sorting vs weighing (by the way the people I asked at the companies mostly weight sorted they think it is close enough -- now this is one person out of many employees there might be those that volume sort too). Is it possible that you did not ask the right question? Maybe you did? If you still have connections with these manufacturers ask them the exact question

Not every one will just offer information especially if they do not know. Make sure you ask the person who's responsibility is quality control. Facts are facts assumptions are assumptions and not good data. I would certainly like to hear what you are told.
Your last sentence sums it up nicely.

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antelopedundee said:

If I was doing that, I'd seat a spent primer anvil side out, fill with distilled water, punch the primers, rinse the cases with isopropyl alcohol, air dry overnight and finally put them in the oven at low heat in one of those pyrex cake pans. Was a piece of cake when I had all of the amenities of a chem lab.

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Dog Rocket said:

I am just wondering what scale the OP is using to measure these cases. Unless he is using a very expensive magnetic force resoration analytical balance, most of the scales used for reloading have a 0.1 grain readability, but a +/- 0.1grain linearity.

It would be interesting to see a test of the OP's method vs. just sorting cases into light and heavy categories by weight.

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