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Accurate measurement of case capacity?

KANEDA SHON

Hello, I am currently living in Japan and I am interested in hunting. I've been learning from various posts on the forum since a few months ago, but there's something I still don't understand exactly. It's about measuring the capacity of a case. As far as I know, the case is filled with water, measured in volume, and then filled in the same volume of powder to measure the capacity. But I still don't know which way is the right way to measure it, so I'm attaching the picture.

Is the case filled with water 100% as shown in Figure1 ? Or is it 100% that the bullet was loaded into the case and filled with water as shown in Figure 2?

I don't have enough knowledge because I just joined. Please help me.
sketch1657984244467.png
 
Take a case and weight it. Then using a syringe fill the case with water right to the top of the neck. Weight the case again and the difference in #'s is the case capacity. Better if you do this with several cases and then average. Most people do it this way. This is how I do it for the #'s I use in Quickload or GRT. I use a fired case with fired primer in case.
 
I believe it can be done both ways. It just depends on which program you're working with and what information it needs to calculate results. The only time I really messed with it, it specified using the results found from your #2 drawing. The base of the bullet to the muzzle represented the Expansion Area. If you're going to measure with water, be sure to put a couple drops of food coloring into it. If you pour water into a beaker you will see air bubbles clinging to the sides. Not good. Food coloring eliminates that. Since you are in Japan, there's got to be a sporting goods store where you can find a worm blower in the fishing dept. Or just get a syringe. Put the bullet in the case, weigh it, then fill through the primer flash hole and reweigh it. That's your case capacity in H2O.
 
KANEDA SHON said:
Hello, I am currently living in Japan and I am interested in hunting. I've been learning from various posts on the forum since a few months ago, but there's something I still don't understand exactly. It's about measuring the capacity of a case. As far as I know, the case is filled with water, measured in volume, and then filled in the same volume of powder to measure the capacity. But I still don't know which way is the right way to measure it, so I'm attaching the picture.

Is the case filled with water 100% as shown in Figure1 ? Or is it 100% that the bullet was loaded into the case and filled with water as shown in Figure 2?

I don't have enough knowledge because I just joined. Please help me.
View attachment 1354959
Click to expand...
Yes, it's #1, the case is filled to the top of the mouth where the water is level (no convexing or concaving of the water) and is considered 100% case volume. Though that is the case volume, it's not the case powder capacity as in you're #2 figure, the projectile takes up some of that space. Measuring the 100% water capacity give you the relative difference between your cases. Your projectiles seated at the same depth will displace the same volume in all the cases. You'll want to be sure your cases are trimmed to the same length to be sure you a good idea of the differences in volume between your cases. Note too that you'll want to measure volume for fired brass rather than sized brass as a sized cases expands in the chamber when fired and that's the volume of interest.

If you're using an app like QuickLoad that helps you with your loading info, it will calculation the amount of projectile displacement and tell you how much powder is actually taking up the available powder space (case capacity) at any particular seating depth.

BTW: to get the water level, it's much easier to see using a flashlight to get a reflection off the surface so you can see whether it's actually level or not. And if overfilled, you can use the edge of a small piece of paper towel of wick off some water to get it level; making it easy to control and get to the level point.
 
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KANEDA SHON said:
Hello, I am currently living in Japan and I am interested in hunting. I've been learning from various posts on the forum since a few months ago, but there's something I still don't understand exactly. It's about measuring the capacity of a case. As far as I know, the case is filled with water, measured in volume, and then filled in the same volume of powder to measure the capacity. But I still don't know which way is the right way to measure it, so I'm attaching the picture.

Is the case filled with water 100% as shown in Figure1 ? Or is it 100% that the bullet was loaded into the case and filled with water as shown in Figure 2?

I don't have enough knowledge because I just joined. Please help me.
View attachment 1354959
Click to expand...
The picture on the right is the ballistic reality but the picture on the left is how the case capacity of a piece of brass is measured.

You don’t need to measure water capacity for ordinary reloading when you have decent reloading data and work up a load starting at safe amounts. Water capacity is mostly used for advanced reloading techniques.
 

Case Volume Determination (pic heavy)

Readers here will see many, many posts regarding determination of case volume. There seem to be about as many different methods as there are posts on the topic, such as using detergent or alcohol mixed with the water, how the primer pockets are sealed, how "full" the case should be filled...
forum.accurateshooter.com

The picture on the left (100%) is what you want to know. You want the water meniscus (surface) at the top of the neck to be as flat as possible and even with the case mouth (i.e. water surface flat, not concave or convex). Backlighting with a lamp makes this much easier as I described in the above post. Although the bullet will eventually occupy some of the useable case volume as shown in your image on the right, it is the total volume of the case you're trying to determine.
 
And to be clear, the measured case capacity does not equal the same value as the powder charge when a projectile is seated.

While measured case capacity is related to the case fill ratio percentage once a bullet is introduced at some seating depth, that is not why it is important.

The actual case capacity is important because it is a direct measurement of the internal volume which is different for standard factory brass and ammo, than it is for your specific fire formed case.

You will find that small differences in case capacity, like the differences between virgin brass versus fully fire formed, can begin to make a difference when the accuracy and distance goes up.

While the increase in internal volume may sound small to some, it begins to make a difference in performance depending on the context.
 
If using QuickLoad, one needs the case capacity measured to the case mouth.

Quickzload calculates the volume displaced by the bullet, including both the part extending below the neck and the part between the mouth and the bottom of the case neck.
 
JB10 said:
Off topic question. Can you hunt in Japan? Or own a rifle?
Click to expand...
Great question.

Not that I do this or that I ever will...
If all your shots are shot over a chronoph and recorded
higher/ lower velocity shots will be visible.
Mark and segregate brass and see if it repeats. If it does cull the brass leaving you with a mean/ consistent batch of brass.
 
David Christian said:
I have one of these gauges and it is great! Very repeatable and way better than water based measurements. Ben is wicked smart and put a lot of effort into building this tool.
Click to expand...
I've been waiting for this tool to come out...glad I saw @murray brook's link.

David - when you stated, "way better", I'm assuming you primarily mean that it's much easier to use than weighing water-filled cases one by one. Is that correct? I can't imagine the accuracy/precision is any better than using water weight, if the weighing process is done properly. However, the major drawback to determining water volume for shooters that use hundreds of pieces of brass is obviously that it would be pretty painful. This tool looks like it would solve that issue nicely.
 
KANEDA SHON said:
Hello, I am currently living in Japan and I am interested in hunting. I've been learning from various posts on the forum since a few months ago, but there's something I still don't understand exactly. It's about measuring the capacity of a case. As far as I know, the case is filled with water, measured in volume, and then filled in the same volume of powder to measure the capacity. But I still don't know which way is the right way to measure it, so I'm attaching the picture.

Is the case filled with water 100% as shown in Figure1 ? Or is it 100% that the bullet was loaded into the case and filled with water as shown in Figure 2?

I don't have enough knowledge because I just joined. Please help me.
View attachment 1354959
Click to expand...
I would go with example 1 because I don't see how you can fill accurately to the shoulder. Example 1 is the standard method. Alcohol has very little surface tension compared to water. It should give better results and repeatability. I have been reloading accurate ammo for a varmint rifle for 50 years and never measured case capacity. Group size is all that you have to measure especially if it’s a hunting rifle. It’s probably a waste of time to measure case capacity for a hunting rifle. 1” groups are good enough for almost any hunting situation. If you measure capacity, what are you going to do with cases outside of some range. Will you throw them away? I would measure the cases as fired and not resized. I wouldn't do it with new unfired cases. I wouldn't worry about carbon residue altering the results. Several guys put charts up on this website comparing case weight to case volume. There was no correlation, just a scatter chart.
 
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If a fellow is capturing accurate muzzle velocity with a chronograph and also using QuickLoad... case volume becomes the third leg of the triad that, together, lets him know what chamber pressures he is running. For me, it's a critical measurement. I can't imagine handloading without it.

Yes, all the way to the top of the neck. And, yes, it's probably the most tedious operation in all of handloading.
 
The program I use uses useable case volume so I measure with a bullet seated.

Seat bullet
Set on scale with a comparator to hold it steady and weigh empty

Fill water through primer hole.
Weigh again.
 
Ned Ludd said:
I've been waiting for this tool to come out...glad I saw @murray brook's link.

David - when you stated, "way better", I'm assuming you primarily mean that it's much easier to use than weighing water-filled cases one by one. Is that correct? I can't imagine the accuracy/precision is any better than using water weight, if the weighing process is done properly. However, the major drawback to determining water volume for shooters that use hundreds of pieces of brass is obviously that it would be pretty painful. This tool looks like it would solve that issue nicely.
Click to expand...
@Ned Ludd, you are correct. I have done meticulous “wet” testing of capacity and it is arduous to say the least. This tool, after warmed up and calibrated gives me virtually the same result in roughly 5 seconds per case. I was one of Ben’s beta testers and have run thousands of cases through this tool multiple times.
 
I was taught sorting by case weight; the volume will go down as case weight increases, of course this was in the mid 70's and haven't changed my way.
 
Bc'z said:
Great question.

Not that I do this or that I ever will...
If all your shots are shot over a chronoph and recorded
higher/ lower velocity shots will be visible.
Mark and segregate brass and see if it repeats. If it does cull the brass leaving you with a mean/ consistent batch of brass.
Click to expand...
That tool looks pretty smart.

I have been using the chrono lately for example a 30.7 charge and by my records is typically running 2939 -2949 ish and one shot says 2911 .. that difference would represent about 3 tenths gr. I mark it and toss that one in a pile to maybe shoot again but probably not.

This might be wrong or might be right, I really don’t know but so far it works for me.
 
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