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Case capacity measuring made easy.


Description

An easy way to measure the volume of a cartridge case.

Since I'm a tinkerer and like to save money where ever I can I will often find myself reforming brass cartridge cases to some other caliber. One key thing for using these reformed cases is comparing the internal volume of the case to genuine cases for the target caliber. 

 

Often folks will just say something like"why bother when you can buy factory brass?" Yea, I get that. Anyhow, sometimes brass is either unobtanium or silly expensive or simply out of stock nation-wide like many components were pst Sandy Hook.

 

I'm also cheap. Why spend money when I can make what I need at the cost of some spare time?

 

As such I'm building a 6.5 Creedmoor upper for a PA-10 rifle. Creedmoor brass runs between 60 cents and over $1 each depending on manufacturer so I'm converting .234 Winchester brass to 6.5 Creedmoor. In the process I'm measuring the case volume so I do not end up with pressure issues as most reformed brass will have lower case volume.

 

So on with the tutorial. This is pretty easy. Let's get started.

 

Set your scale to read in grams. Be sure to zero if needed.

 

You will need the brass you want to use. Reformed and trimmed to size. Be sure you also have a junk primer seated. In this case I used 4 different cases in addition to the new Starline 6.5CM brass I bought.

 

Weigh each case empty with the spent primer seated. Here's the Winchester case empty:

 

water1.jpg

 

Next, fill it with water. Weigh.

 

water2.jpg

 

Do the same for the rest. Be sure to write down the numbers.

 

water3.jpg

 

Now just subtract the empty weight from the full weight. This will give you a number in grams. The good news is converting grams of water to cubic centimeters is easy. 1 gram of water weighs 1 cubic centimeter.

 

The new Starline brass was weighed earlier. The case capacity is 3.33cc so it's within 1% of volume on all but the PMC brass.

 

I hope this was helpful.



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