Accurate way to check case capacity?

[Savage Lover]

What are some of the most accurate ways that I can check my cases capacity? I have heard of using water and measuring how many cc's it will hold or just filling full of powder and weighing each charge. You guys have any other ideas or just what works best for you?

Thanks

 

[DBailey]

I just take a clean sized case, prime it with a spent primer, and then place it on a digital scale.
Zero the scale with the empty case on it.
Using a syringe, fill the case with water to the top of the neck. Be careful not to overflow it.
The scale should be displaying the weight of the water needed to fill the case.

 

[338Lapua]

Use your established bullet seating depth for the particular bullet your using.
Weigh one case with the bullet seated to proper depth without powder or primer.
Now fill the case with water up to the top of the flash hole through the primer pocket using a hypodermic needle and weigh again
Now subtract dry weight from the water weight and this will give you your case capacity….. The water shouldn’t leak out when you weigh it.

 

[Savage Lover]

Sounds simple enough, thanks guys.

 

[RonAKA]

Have only done a few as a test, but my plan is to use a fine powder. Fill the case while dropping the powder from a uniform height, level it off, and pour it into the scale pan to weigh it. Powder is then dumped into the next case and so on... If you do the filling inside a bowl, then any powder that spills is contained.

The water method should work, but I have concerns about accuracy and time to do it. Each case would have to be weighed dry, then full of water, with no water on the outside, and capacity determined by subtraction. I don't even think I could do that on my balance beam. Would be water everywhere.

 

[spclark]

If leaks are your concern you can reliably work with cases neck end up. Easier to fill this way & the spent primer seals the flash hole.

Othewise, on a clean case close the neck end with a piece of clear packing or masking tape. Plenty enough adhesive to seal off the opening as long as the case is neck down on your digital scale platform. Folks who use balances have a rougher time of it....

A tip: add a drop or two of liquid dishwashing liquid to a glass of water for your reservoir, the detergent helps cut surface tension & allows the water to better fill your cases & any air bubbles to be released.

 

[nfhjr62]

Take a look at this post http://bulletin.accurateshooter.com/2011/04/overbore-cartridges-a-working-definition/ has a chart with Cartridge Grains Capacity for 33 different cases

 

[338Lapua]

Would be water everywhere

With the bullet seated you have a water tight seal at the case mouth, as the case is filled, air escapes replaced by water. No matter what angle the case is held after it is full of water it cannot escape. until the bullet is released.

 

[TheSnake]

Use your established bullet seating depth for the particular bullet your using.
Weigh one case with the bullet seated to proper depth without powder or primer.

338Lapua,
Why would you only fill to the bottom of a seated bullet? I fill mine up to the top.

I place Scotch tape on the bottom of the case without a primer and fill with water from the neck. The primer pocket does not get any water because of the small flash hole and no way to dissipate the air sealed by the tape.

 

[338Lapua]

The area were the bullet is seated is filled with bullet mass. So to fill to the top of the neck with water would give you a false capacity in my opinion.
The way described would be a better way of detecting your real case capacity.
especially If your trying to determine a optimum load density for that case.

 

[4xforfun]

The area were the bullet is seated is filled with bullet mass. So to fill to the top of the neck with water would give you a false capacity in my opinion.
The way described would be a better way of detecting your real case capacity.
especially If your trying to determine a optimum load density for that case.

So, do you weigh and sort all of your bullets by bearing serface first before testing for case capacity? If you have two bullets with differant bearing serface lengths, you will have one bullet with more (or less) mass inside the case, giving you inaccurate volumes for your case.

Also, when you change bullets, do you re-test?

 

[necchi]

The area were the bullet is seated is filled with bullet mass. So to fill to the top of the neck with water would give you a false capacity in my opinion.

Not really, your introduing a variable that would apply to ALL cases of that caliber trimmed to the same length and using the same bullet.
The function here is to determine the volume variable of the cases at hand, seating depth is simply another, while related, differant variable.