• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Case water weighing procedure ?

Curious as to what procedure everyone is using for water weighing cases. I am using the below item from 21st Century

http://www.21stcenturyshooting.com/Primer_Pocket_Plugs.php

Am also using an analytic balance for weighing. I've tried an eye dropper and a styringe for dispensing the liquid into the case. I have tried using water, 91% isopropyl alcohol, rubbing alcohol, H2O with a surfactant but am still having problems getting consistency. I weigh the case 5 times and there is quite a lot of spread.

So how do you guys do it ?
 
Are you allowing for surface tension?
Air bubbles?
https://www.youtube.com/watch?v=NMEtfT-e0eg
 
I am trying to control the meniscus by using liquids with very low surface tensions (alcohol, H2O with a surfactant, etc.). In looking at the video and based on what I have done so far I can say that the guy's technique would lead to a lot of repeatability problems if he would weigh the same sample 5 times. I also wonder what he used to plug the flash hole. Primer maybe ?
 
I wonder how consistent a fine granular material would be, something like ball powder, vibrating the case, and striking it off with the edge of a credit card?
 
I use dental wax to plug the flash holes. When I'm done it come out easily by just warming the base of the case for a few seconds with a Bic lighter, then using a tooth pick or dental pic.
I hope this helps,
Lloyd
 
zip,

I tried the water method and had similar results all over the place. Then I figured that if I want to know the percent fill of a particular powder, why not fill the case with that powder? ??? So, I did and got (IIRC) 33.2 grains of LT-32 in my 6BR. I'm loading 29-ish grains of LT-32 and that gives me about 89% case fill, just slightly above the "magical" 85% fill. The gun shoots lights out if I do my part. Give it a try; it's a LOT easier and more consistent, too. 8)

Dennis
 
Stupid questions, I'm not trying to be a smart @$$, but have you checked the repeatablity of your scale. If it's electronic, could you be getting RF or dirty power. Just some wag's. Paul
 
Take your fired case, insert an already fired primer into it, weigh it. Fill with water from faucet, weigh it, subtract one from the other. That's your gr water capacity.

This is a universal measuring system that is used world wide, water is the liquid used.
 
Never plug your flash hole with anything that is not a primer unless you know that it does not change the volume of your case since this is the whole purpose of the exercise.

Your problem is likely due to your inability to get your meniscus to a consistent flat level which is what you should strive for again since you are trying to determine accurate case volume.

The best way I know of in terms of technique is to get the volume close and then use an 18 gauge or finer syringe to inject in the last bit of volume. You do this with a desk lamp on in front of you and the case between you and the lamp. Look at the reflection of the lamp on the surface of the rubbing alcohol using a head magnifier at the case neck. The reflection will begin to enlarge if you are under (concave shape) or over (convex shape) in terms of volume. When the reflection is small and correct in size/shape the meniscus is flat. Strive to get this consistent look and you will have a consistent volume/weight.
 
Most references stipulate "filled to overflowing."

According to a chap I respect over on the Nosler forum, "filled to overflowing" means literally until the the meniscus bursts and water flows all over the place, which means you have a bulging hemispherical-shaped meniscus just before it bursts. He also states the water should have been boiled, or left in an open container for 8 hours, before testing with it, to have the proper, repeatable surface tension.

However, others say you add drops until the water is dead level with the case mouth (before the meniscus bulge starts forming) but that's certainly not "overflowing". I believe this is how Ken Howell does it. This is what makes more sense to me.

I'm not sure what the definitive answer is, and when checking cases against published H2O capacities for the same manufacturer's cases, I have had trouble replicating the published results using either method, frankly. I finally gave up and don't fuss with it.
 
gstaylorg,

I lean towards your level-with-mouth idea, and it's not rocket science either way, but as I stated, other authoritative sources state emphatically the bulging meniscus should be weighed as well.

Can you provide a reference which might convince me?
 
Again, I don't disagree with you. But as you point out, it doesn't matter what the specific procedure is, as long as it is a convention, and everyone follows it. I also agree it doesn't make much sense to measure the water outside the case, but knowledgeable folk state it is the proper way to fulfill the "filled to overflowing" stipulation consistently. If I was hearing that from obvious rubes, I would dismiss it as preposterous, out of hand. But I'm not hearing it from rubes.

So, until I can find an authoritative reference document of some sort (something from SAAMI would be nice!) I'm holding my cards.
 
Been a long time since I did this, so I have nothing of value to add. I will start doing it as I get back into reloading though. Want some more input? There is only one page of replies here so far. There is 9 pages on LongRangeHunter.com.

Bob
 
rkittine said:
Want some more input? There is only one page of replies here so far. There is 9 pages on LongRangeHunter.com.

Guess I'll have to go search for it there. But just out of curiosity, is there a consensus there on overflowing vs level?
 
You will have fun reading through everyone's take and method. I was getting weary, but could not find a consensus.

Bob
 
rkittine said:
You will have fun reading through everyone's take and method. I was getting weary, but could not find a consensus.

That's what I figured. Thanks, I've already got all the inconclusive discourse I need right here. ;)
 
I think the word “overflow” is the source for all the confusion. The reason being is if you look at the QL literature, it specifically ask for “Maximum Case Capacity, overflow”. This can of course be interpreted as “fill the case to the point that it will overflow”. However, there are a few problems with this.

1) The biggest problem is using the volume that includes the bubble at the top makes no sense whatsoever. For example on page 64 where it talks about “volume occupied by seated bullet”, what has the “case volume displaced by seated bullet” has to do with that extra case volume?

2) The volume that literal “overflow” occurs depends on the fluid being used because it is affected by surface tension and this is different for different types of fluid – for example, rubbing alcohol has lower surface tension than water and will overflow at a lower volume.

3) To get to that overflow to spill volume, you will have to fill to overflow every time and wetting the outside of the case will of course give you false data and any attempts to dry the outside frequently cause a spill of the “bubble” of water at the top.

4) When the liquid spills depends not only on the surface tension but also the shape and surface of the case mouth which means a lot of variability can come into play.

5) The other problem with this intrepation is when I look at the default value for something like .223 Rem (SAAMI), the value is 1.870 cm3. That value is so under valued for all the types of 223 cases that I have measured using the more conservative flat surface meniscus that it is hard to believe that it could be the “overflow” value.

So my intrepation of “overflow” is “fill to just at the point of overflow” which I see is just past when the fluid level is flat.
 
I have been scratching my head about this all day. It seems like such a simple thing. How hard could this be and yet we are still scratching our heads. Anyway here is what I came up with today. Feel free to shoot me down if this sounds crazy :-)

When sorting our brass by estimated case volume we really aren't interested in the volume of the entire case. Just the volume of the part of the case that is under the seated bullet. So why are we trying to measure the volume of the case up to the top of the neck ?

How bout this idea.

1. Size test case and neck to final size and trim and chamfer neck after depriming, tumbling and annealing.

2. Take a test bullet and wet sand down the bearing surface so that it will easily slide into the test case neck with very little tension but just enough to seal the case with water in it.

3. Place test case in press and seat test bullet to normal seating depth.

4. Now turn test case with the seated test bullet upside down and place in some sort of stand with case head facing upward.

5. Place test case with seated test bullet and stand onto scale balance pan and tare weight to zero.

6. Remove test case, test seated bullet and stand from balance.

5. Use syringe with needle to fill case thru flash hole with 91% isopropyl alcohol (low surface tension liquid)

6. Fill to the point that alcohol just comes to the top of the flash hole

7. Place test case with test bullet and stand back onto balance pan and weigh to the nearest .1 grain.

8. Record weight and remove test fixture.

9. Pull test bullet from test case and dump alcohol back into bottle.

10. Wipe off test bullet and start process over again on next test case.
 
It’s a good idea from the standpoint of filling from the bottom via the primer hole instead of the case neck. The reason this is a good idea is because the small the hole diameter, the less degree of potential error. This is the reason why it is harder to get good case weight – case volume correlation for a 308 case compared to a 223 case.

The one potential weakness of this method as stated is I am not sure a bullet that can slide in with little neck tension will seal the case good enough to prevent rubbing alcohol from leaking out – this is due to the lower surface tension of isopropyl alcohol. Water might not leak but you will likely have problem with air pockets due to its high surface tension.
 
Now you are making rocket surgery out of it!
To 'overflow' means full, and no more.
Put of smidge of alcohol in water that has sat in a bowl for a day(stir once in a while to deaerate). This reduces tension not only at a formed meniscus but at all contact points within the case.
Once you carefully(slowly) fill to the case mouth to form a meniscus, you touch it with a tissue corner to flat(as observed with the right lighting for this). This is QL reference 'overflow'.
This is an important baseline, and it assumes the cases are fully prepped, trimmed to same lengths, and fully fireformed to stable dimensions(not FL sized). Otherwise, your method and measure is wrong.
I say this because once you FL size your cases, and they springback to whatever, you're adding variance to H20 capacity that doesn't exist otherwise. Now you might want just this, but prepare to expand your tolerances with it, and accept that it doesn't actually represent case H20 capacity.

QL adjusts this overflow capacity based on the entered bullet type and seating depth(volume occupied by seated bullet). This is exactly what it should do, nothing wrong there. If you're not using QL, and you just want consistent H20 capacity cases, then there is no gain in determining volume occupied by your bullets, and overflow provides true H20 capacity.

In the past, I've stood cases with a plastic golf tee fit into the flash holes, and this always worked well. I'm going to try the 21st Century pocket plug before long, as I'm sure it will work as well.
Someone suggested we shouldn't measure H20 capacity tighter than powder measure and I agree. There is no gain in that. So any halfway decent reloading scale is fine. Lab balances are not reloading scales,, they make terrible reloading scales.
 

Attachments

  • Tee.jpg
    Tee.jpg
    51.9 KB · Views: 51

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
165,795
Messages
2,203,589
Members
79,130
Latest member
Jsawyer09
Back
Top