Testing the Testing

[pjifl]

Certainly much lower surface tension than water - but no lower than a whole lot of other organic solvents including Ethanol, Methanol. While we consider water is a typical liquid, in fact it has many freakish properties. My fluid experiments with a fluid used methylated spirits. This also has issues with known density and change of density during storage and temperature changes but I am beginning to doubt that IPA has any real advantage except sounding 'scientific' and 'exotic'.

In general, low surface tension goes hand in hand with higher evaporation rates.

[Gyro]

I wonder if it may work to use an 'evaporative' fluid, but instead of grappling with a meniscus how about just place a ball bearing in the case mouth ? Then weigh the filled case along with the ball bearing. Obviously the case mouth would benefit from having been well prepped so it formed a nice seal. Plus the excess fluid that the bearing displaced would need to be cleaned off. Or even evaporated away ?

I guess here we are just designing the testing method ?

[pjifl]

Topping with a steel ball is an interesting idea. Unfortunately, it does nothing to address the problem of different batches of fluid having different densities, nor temperature variations. It would allow the use of water - but there is the problem of bubbles which is minimised with the wetting action and surface tension inherent in Alcohols.

Special scientific glassware for measuring SG of fluids incorporates a special stopper with a very small diameter opening.

Here is an example of a certified accurate volume SG Bottle but again this principal does not solve fluid density issues unless you calibrate your fluid every time you do a batch at constant temperature. It is worth reading the specs, noting refinements.

https://www.ebay.com/itm/Specific-Gravi ... rwLRL_cpNw

https://www.ebay.com/itm/SPECIFIC-GRAVI ... Swo0JWKXNu

[PeteFox]

OK, so another way of doing this.

Dunk a group of unprimed cases in a tub of water and swish them through the water end to end to remove any bubbles.

Whilst in the water insert into the case mouth a watertight stopper with a flange large enough so the case will stand up upside down. Remove while keeping upside down, dry off case and remove the water in the primer pocket with a syringe. Then weigh and subtract the known added weights. If the stopper were machined to imitate the base of a fitted bullet (boattail, seating depth etc) the exact volume of the case available for powder can be calculated.

Each case would have to be individually identifiable with its weight recorded for this to work.

This will eliminate three things
1. Air bubbles
2. The meniscus
3. Wet cases adding to the weight.

Pete

[Gyro]

Yes Pete but sounds awfully messy.

The SG/RD of the fluid used would need to be measured of course. Plus control the temp.

It would be nice to get a test method that was agreeable to all/most then undertake the tests. I would mostly like to get a handle on the case weight vs volume problem, because I really don't want to be shagging around volume checking all that brass. But perhaps the test could be refined so it became feasible ( timewise ) to volume check a big batch and get rid of the outliers ?

[pjifl]

This whole process has raised some worthwhile issues.

But is it being driven just a bit too much by having too much time on our hands - myself being as much to blame as anyone else.

A terminal case of having too much time on ones hands is illustrated by

https://www.youtube.com/watch?v=nORRgU8sGdE

[pjifl]

I must apologize for the previous post. Bit off topic.

I will attempt to investigate variations of density in some commercial IPA and how it changes over the next few weeks. I have a gallon of supposedly Anhydrous (100%). Used for many things including cleaning Lenses. There may or not be a problem and I think there is only one way to find out - but it will take time.

Peter Smith.

[PeteFox]

Yes Pete but sounds awfully messy.

Gyro, you're hard to please, it's only water.
Density varies by bugger all up to 25degC.
Pete

[Gyro]

I know Pete. The title of this thread contains the substance of what is a real problem in this shooting game which is that it’s actually REALLY HARD to prove theory. But we do like to try. And the top guys who win the big shoots are mute. Good on them !!!

[pjifl]

OK. I have managed to find some of the work we did many years ago on weighing cases and have produced a small pdf document summarizing our findings. You can download it at

https://sites.google.com/site/pjshootin ... xperiments

There are a few other experiments that some should find interesting. I will see if I can document them briefly.

Peter Smith.

[ajvanwyk]

OK. I have managed to find some of the work we did many years ago on weighing cases and have produced a small pdf document summarizing our findings. You can download it at

https://sites.google.com/site/pjshootin ... xperiments

There are a few other experiments that some should find interesting. I will see if I can document them briefly.

Peter Smith.

Very interesting Peter, thank you for sharing.

[pjifl]

Since I have found some old material, I am putting more up. At least then I will know where it is. Added to the same site

https://sites.google.com/site/pjshootin ... xperiments




is a rather interesting article on Barrel Mirage. The results are probably unexpected.

[Gyro]

Loved that one Peter thanks !

So what about the old saying “ never shoot in a boil “ ? Does your experiment relate to that theory i.e. is the saying about possible sighting error problems occurring or is it believed the heat waves ( which during a boil are clearly seen to be rising ) will carry the bullet upwards, or at least relatively more than normal ?

[wsftr]

Loved that one Peter thanks !

So what about the old saying “ never shoot in a boil “ ? Does your experiment relate to that theory i.e. is the saying about possible sighting error problems occurring or is it believed the heat waves ( which during a boil are clearly seen to be rising ) will carry the bullet upwards, or at least relatively more than normal ?

On some ranges this is the worst advice I have ever heard...based on me following it and regretting it badly.

[Gyro]

http://benchrest.com/showthread.php?602 ... iffraction