Pneumatic case volume measure

[ADIDAS69]

I am aware of the other methods of attempting to discover and record internal case volume measurements. I am trying to develop a means of using air preasure. The one detail I've come across that is a pain is the gauge. I've been hunting for a digital psi gauge the will give me a .000 reading the Ashcroft DG25 is looking like the superior choice but is $300+ dollars. I am hoping to find a gauge in the $150.00 ish price range. If any of you all know of a gauge that'd be worth owning in the price arena I would love to know too.


Thanks

 

[FlyFish]

I'm afraid I can't help with your question, but just in the interest of furthering my own education, how do you go about measuring case volume using air pressure? Thanks.

 

[1100 tac]

Yeah, that is an interesting question...

 

[us920669]

Seems like volume of liquid would be the most precise. I have wondered, do you measure to case neck, bullet base as seated, when it hits the lands, or ...?

 

[F. Guffey]

Fluid flows, water flows because it is a fluid. Water can not be compressed.

Air is a fluid , air flows and air can be compressed.

F. Guffey

 

[FlyFish]

Fluid flows, water flows because it is a fluid. Water can not be compressed.

Air is a fluid , air flows and air can be compressed.

Indeed, water and all other liquids are incompressible (not exactly, but close enough for most purposes) and the behavior of air and other mixed gases under changes in pressure can be approximated by the ideal gas law, but I'd still like to know the procedure for using air pressure to measure case volume. If you know it, please share.

 

[polyphemus]

Just holding a constant accurate T and sealing the cases might prove a tall order unless you have a a lab and a highly controlled environment.What will you do with the results if you are successful?

 

[F. Guffey]

The request reminds me of case neck tension. I have tension gages, all of my tension gages are calibrated in pounds and no one will share a conversion chart for converting tensions to pounds. That leaves me with measuring bullet hold in pounds.

I can measure crush fit or interference fit, there was a time I had a press that measured PSI meaning I could measure the amount of effort required to press a sleeve into a cylinder,

Then there is your request, seems the volume would be determined first then the gas when compressed into a liquid could determine volume at PSI.

And then; someone is going to bring up variables then say ‘it can not be done’.

I would suggest you contact the manufacturer of bottled gas containers like propane, butane oxygen etc. and then someone could ask; “How do they do that?” They compress a gas in to a liquid and ‘sort of’ verify. They weigh and check pressure and they know the column of the container, then there is purging.

If the tank is not purged with a vacuum ‘forget about it’ but if a non compressible is used the container is purged when the air is displaced with the liquid.


F. Guffey

 

[F. Guffey]

I do have a pressure gage that measures pounds of pressure in .01 increments I also have pressure gages that measures distance, problems they must be calibrated to pressure. That brings us back to variables.

F. Guffey

 

[F. Guffey]

http://www.ashcroft.com/products/pressure_gauges/digital_gauges/dg25-digital-pressure-gauge.cfm

F. Guffey

 

[T. O'Heir]

Do not spend $300 or even $150 for something will tell you nothing you need to know. Case volume isn't really something you need worry about anyway.

 

[Mike38]

To the OP:
There is a device that will measure the cubic centimeters of an internal combustion engine using air injected through the spark plug hole. Is this the same theory as what you plan on case volume?

 

[jmorris]

I always used a pipette and water but there is nothing to invent there.

Same thing although starting with a graduated cylinder when "CC'ing" combustion chambers on cylinder heads.

 

[ADIDAS69]

T. 'Oheir: I agree there is dubious value to sorting casings by measured internal case volume but I've seen it discussed and seen different methods discussed and they all have the same issue of being simply impractical. All resulting in the need to dry and or re-tumble the casings or just being stupidly time consuming. I can't help but want to provide a better solution that would actually be feasible for high volume (500 + shells) re-loaders.

Mike38: Yes basically the same concept. whilst the actual measurement isn't that important, being able to sort shell casings by consistency could be useful. Though the easier solution is to just buy all one brand of brass, it is not a leap to believe that any one specific manufacture's production process would have to be inherently consistent.

Polyphemus: the pressure used will be very very low around 5 PSI. The seal will be easy to maintain. The device would be intended to be used on casings that are already re-sized, re-primed and trimmed and chamfered. Assuming success the goal would to be to increase potential for accuracy buy increasing the consistency of loaded ammunition. Whilst there is a whole lot else that might have greater impact on the final results of a fired projectile, I get bored easily and this is something to work on. Note that yes i have given what i can and or would be taken to better pursuits like landing men and women on mars; and i don't do RC models or cars.

Side note, I am not a big fan of colonizing mars as we would have to create an artificial magnetosphere to really make it work and I would prefer we focus, as a species, our energy on worm holes or faster than light travel or some such so that we could get to planets worth colonizing.

 

[F. Guffey]

I'm afraid I can't help with your question, but just in the interest of furthering my own education, how do you go about measuring case volume using air pressure?

Flyfish, I had a neighbor that built pipe organs, he made the pipes out of lead and or wood. He also built telescopes and lenses for spy type equipment. When tuning the pipes he used sound. I had never thought of using air to measure case volume, and now? I wonder; is it possible to blow air across the case opening to make that sound. I understand a pitch perfect ear is rare but equipment is available when tuning musical instruments. Then there is equipment that measured decibels, I do not know how accurate the equipment would be when discerning volume. I doubt any method or technique would measure volume unless a set of standard cases were used.

F. Guffey

 

[us920669]

Brilliant! What you would measure is not volume but pitch, and there certainly is equipment that could do it. It would be a lot of technology for something that can be done much more simply. If we get a gun-friendly administration, you could apply for a grant. It probably could be built into a progressive press to detect an overload.

 

[Jim243]

attempting to discover and record internal case volume measurements. I am trying to develop a means of using air preasure.

?????? Are you trying to measure volume or pressure. 10 cc does not translate into 10 psi. Both measurements are unique and not necessarily related to each other. You will need to make sure you are using 1 atmosphere on each test to get any comparable results.

But where there is a will there is a way. Try this, take a syringe and remove the needle. Without using excess force, place the syringe over the mouth of the case and press down. When you can no longer compress the air in the case, note the reading (scale) on the syringe. This should give you a good idea as to the amount of volume within each case. It may not be scientifically accurate but should give you a comparison.

Good luck and stay safe.
Jim

 

[F. Guffey]

And if I wanted to change the pitch I could shorten the case.

I am the one that matches case by head stamp. If I start with 20 cases in a box the cases stay together through there little short lives.. I have absolutely no interest in measuring volume. I do not have new Winchester cases, in the old days I could count on Winchester cases haveing a larger volume by weighing them.

F. Guffey

 

[Lost Sheep]

The request reminds me of case neck tension. I have tension gages, all of my tension gages are calibrated in pounds and no one will share a conversion chart for converting tensions to pounds.

F.Guffey, I have seen you use the term "tensions" before.

What is a tension?

Lost Sheep

 

[ADIDAS69]

Jim243: The testing area is my furniture making facility that is windowless and has continuously controlled heat and humidity. You're correct that the device would be measuring PSI which would be used simply to sort casings for matching volume. The actual cubic centimeter volume isn't what i am worried about. I originally had the thought of adapting a nail gun in some way but will in fact be using a syringe connected to 1/4" ID brass pipe.

Aside from just wanting to solve a problem i, as i am sure all of you, have experienced ridiculous fluctuations in brass of my choice being readily available. so this would help deal with having to use range pick ups and resisting over specialization.