Digital case volume meter

[Webster]

How much would long distance shooters be willing to pay for an accurate digital case volume meter? No more messing with liquid and the associated clean up. Much, much faster volume sorting of cases. I have the design complete and should have a prototype built and tested by Christmas. I will have to machine the parts on my CNC mill.

Digital tubing micrometers can run into hundreds of dollars. Would $250 be too much for something that has heretofore been non-existent and will do the job accurately, quickly and efficiently?

Ron

Using JLOW’s numbers. Cartridge not given.
Avg. case wt. = 49.58
Range = .47 - .95

The range in weights is about .24 above and below the median. This is a variation above and below the mean of about 0.48%. The general rule is that you have to measure with a precision of at least one order of magnitude better than the final result your looking for. In other words you would need sensors and associated electronics that would measure whatever you are measuring with an accuracy of about 0.048% error or better. I don’t think it’s possible to buy the appropriate sensors. How much would temperature and barometric pressure affect results? Pardon the math if it is not exact. Where I worked we had small precision electronic devices that measured torque required to rotate two surfaces against each other. They cost about $15K.

 

[lrgoodger]

solidworks has a program that calculates internal volume. expensive. not sure how it could take into account the variations in brass thickness which is the real cause of variations in internal volume

That is only the INITIAL cause of variation when the case is new. You could wind up with more variation caused by your resizing die adjustments and inconsistencies in applied resizing force. Then there is the well accepted constant increase in carbon layers added with each firing. That is one potential way of adjusting individual case volumes to get a matched set for competitions. If you have a case that has a bit higher volume than the rest of the set, just fire it an additional time or two to bring the volume down. This factor is the biggest single reason (although there are more) that I and many other shooters keep brass segregated by the number of firings on them.

 

[jimbires]

will one tool work on any case , or will adapters be needed ?

 

[lrgoodger]

will one tool work on any case , or will adapters be needed ?

One tool will work for all cartridges with a .470 head diameter, including rebated cases like the .284. The .223 would need a bushing, but who shoots 1000 yards with a .223?

 

[4xforfun]

.....or spend your $ on another wind flag.

Sure....I've seen it a hundred times...buying a new wind flag helps my ES.

 

[LC Tikka]

....Once the case volumes are measured and the variations known, for some shooters the next critical step may be to make all volumes the same, otherwise what has been achieved. Sorting by volume also has a tolerance of choice.
Having cases of "equal volume" fixes one key element in achieving better accuracy.
How the volume of a case is easily and accurately changed is the next important question IMO.
LC[/QUOTE]

Don't let this subject fade away, there must be some good engineering ideas out there to safely mod the inside of a case to change volume.
LC

 

[KenOath]

How much would long distance shooters be willing to pay for an accurate digital case volume meter? No more messing with liquid and the associated clean up. Much, much faster volume sorting of cases. I have the design complete and should have a prototype built and tested by Christmas. I will have to machine the parts on my CNC mill.

Digital tubing micrometers can run into hundreds of dollars. Would $250 be too much for something that has heretofore been non-existent and will do the job accurately, quickly and efficiently?

Ron

If it’s accurate, fast and reliable I’m in.. curious to see this new contraption, you will sell more if it looks cool to!!

Cheers Rushty

Edit- This could be as revolutionary as Adams Auto Throw...I would of paid more for that thrower..Just don’t tell Adam that!!

 

[spclark]

This could be as revolutionary as Adams Auto Throw...

Different aspect, in that it’s possible to throw then trickle charges up as accurately as Adam’s device can, it’s just not at all convenient. Why Prometheus or Gunderson powder dispensing technology was such a revelation twenty years ago.

Internal case volume OTOH is something we’ve had to accept as a given; we can tediously measure it then sort cases accordingly if deemed necessary, but as an aspect over which we have some control?

Not yet... at least not quite yet, until
we learn more about what the OP has up his sleeve....

 

[KenOath]

Different aspect, in that it’s possible to throw then trickle charges up as accurately as Adam’s device can, it’s just not at all convenient. Why Prometheus or Gunderson powder dispensing technology was such a revelation twenty years ago.

Internal case volume OTOH is something we’ve had to accept as a given; we can tediously measure it then sort cases accordingly if deemed necessary, but as an aspect over which we have some control?

Not yet... at least not quite yet, until
we learn more about what the OP has up his sleeve....

Very true, but it certainly felt revolutionary compared to my old powder charging process..

Cheers Rushty

 

[spclark]

Very true, but it certainly felt revolutionary compared to my old powder charging process..

No arguement here with that statement! I’m an Adam fan too.

 

[dkhunt14]

Make a prototype, then repeat my test. No one who has posted has shown or mentioned any on-target information that validates the concept. That doesn't mean you should not do a test. I would not go into production without a prototype and on-target proof of concept. My testing was at 100 yards, since that's the longest indoor range I know of. You will not be able to demonstrate a 1,000 yard improvement due to variations in wind, which is greater than the effect of the variable being tested (case capacity), and that will make testing invalid under those circumstances.

You can test if you run a ladder, color the bullets and shoot like a match. It shows up. All you got to do is repeat to see if It repeats. It doesnt take much for an inch difference at 1000 yards in A Dasher. Benchresters would benefit more due to rate of fire and the small amount of group size you can lose a match by. (sometimes a .001) Matt

 

[Webster]

How much would long distance shooters be willing to pay for an accurate digital case volume meter? No more messing with liquid and the associated clean up. Much, much faster volume sorting of cases. I have the design complete and should have a prototype built and tested by Christmas. I will have to machine the parts on my CNC mill.

Digital tubing micrometers can run into hundreds of dollars. Would $250 be too much for something that has heretofore been non-existent and will do the job accurately, quickly and efficiently?

Ron

How about a general description on how it works?

 

[lrgoodger]

How about a general description on how it works?

Without giving too much away, I can describe the procedure for measuring a case.

First you adjust the fixture for the case height. (30 seconds - once set it does not change unless you change case type)
Then you clamp the case in the fixture. (2 - 3 seconds)
Turn the display on and turn a knob (or push a button - not finalized yet) to actuate the reading. (2 - 3 seconds)
The reading should be stable within a couple of seconds.

The key is going to be repeatability on a single case. That is where the crux of the design lies. The sensor is so sensitive that putting your finger on the fixture in the right place will result in the reading climbing steadily due to temperature rise from body heat. When measuring a set of cases, you would want to maintain a steady room temperature. Once the prototype is done, I will have to test to see how much variation can be caused by holding the brass case too long in the hand, thereby warming the case. It might be necessary to wear a glove when placing the case in the fixture to minimize heat rise in the case. Don't know yet.

 

[6BRinNZ]

Without giving too much away, I can describe the procedure for measuring a case.

First you adjust the fixture for the case height. (30 seconds - once set it does not change unless you change case type)
Then you clamp the case in the fixture. (2 - 3 seconds)
Turn the display on and turn a knob (or push a button - not finalized yet) to actuate the reading. (2 - 3 seconds)
The reading should be stable within a couple of seconds.

The key is going to be repeatability on a single case. That is where the crux of the design lies. The sensor is so sensitive that putting your finger on the fixture in the right place will result in the reading climbing steadily due to temperature rise from body heat. When measuring a set of cases, you would want to maintain a steady room temperature. Once the prototype is done, I will have to test to see how much variation can be caused by holding the brass case too long in the hand, thereby warming the case. It might be necessary to wear a glove when placing the case in the fixture to minimize heat rise in the case. Don't know yet.

any chance of an international ship?

 

[lrgoodger]

any chance of an international ship?

Of course, as long as the purchaser pays shipping.

 

[nmkid]

I don't know if I can take the waiting!! Already waiting on the release of a new metal detector and now this!!

 

[lrgoodger]

I don't know if I can take the waiting!! Already waiting on the release of a new metal detector and now this!!

Metal detector? Hah! You're dabbling in one of my old hobbies. Perhaps you saw the true story I wrote for Treasure Magazine back in the early 1990s. The name of it was 27 Days Digging Decatur. The magazine went out of business shortly after it was published, so I put it online at my website at Geocities. I thought it was lost when Geocities closed up, but some guys salvaged a lot of Geocities, so it can still be seen at http://reocities.com/athens/acropolis/4052/. Click the Metal Detecting tab at the top and you will see the covers of the four issues in which the story was published. Then click the 27 Days Digging Decatur button at the top of the left column to read the story.

 

[jlow]

Sounds interesting and perks my scientific mind.

My guess is the case is clamped between two surfaces that seals each end. Pressure is equalized and a very accurate amount of air is injected into the case, the increase in pressure inside the case is a function of the volume of the case and if measured accurately will give you the volume. It is of course calibrated by doing the same thing to a calibration standard of known volume.

I would also argue that the actual volume of the case is irrelevant since reloaders would have zero use for that number, what is important is relative difference so the thing can actually just give you some absolute number.

Not blocking the primer hole with a consistent plug could potentially cause some error as if the bottom of the case i.e. it's head is where the seal is, variation in the volume of the primer pocket could play into the final number but its not a real factor relative to case volume?

The material sealing the top and bottom of the case is critical since slight differences in clamping pressure could compress the material differently and affecting the volume of the sealing material that intrudes into the volume of the case?

Just thinking out loud because that's how my brain works....

 

[seymour fish]

TESTING what?
The OP has said he has a tool to easily and accurately measure case volumes, nothing more. This tool will need testing for consistancy etc.
Once the case volumes are measured and the variations known, for some shooters the next critical step may be to make all volumes the same, otherwise what has been achieved. Sorting by volume also has a tolerance of choice.
Having cases of "equal volume" fixes one key element in achieving better accuracy.
How the volume of a case is easily and accurately changed is the next important question IMO.
LC

Yep, the water method is free, and plenty accurate, and takes much less time than say turning necks, so it would need to at least match that precision, while being much faster. Nevertheless, I am all ears

 

[LC Tikka]

How do weight sorted cases compare, once the volume is checked.
LC