Case capacity question

[RockyMtnMT]

I need to figure out the case capacity of a cartridge in grains of water. When you fill the case w/ water, do you fill it to the top of the neck? Weigh the empty case, weigh the full case, and do the math?

Thank you, Steve

 

[boomtube]

Rocky, I don't think there is a "standard" way to do it. What makes the most sense is to measure the powder chamber of the case, that is to the base of the neck. Of course if you seat long it would include a short section of the neck too.

I have done it by weighing the dry case first, then filling it to the base of the neck with a hypodermic type oil dispenser. If I over did it (which I did) I could also suck the excess out!

 

[johnnyk]

I know this doesn't answer your question but maybe your case is included in this list and it will help your endeavour....Good luck...JohnnyK.

Rifle Cartridge Case Capacities

 

[AJ Peacock]

I've always filled them up to the top of the neck (as full as I could get it). I've used the capacity in Quickload and the velocities have always been very close using this method.

AJ

 

[jwp475]

Which case are you interested in, perhaps I can give you the water capacity..

 

[RockyMtnMT]

Well, I guess I will get two measurements. One to the base of the neck, and one to the top of the neck.

Thank you for the help, Steve

 

[J E Custom]

Steve

The standard way to measure a case for case capacity is to fill the
case all the way to the top of the neck as others have said.

The reason is accuracy (it's hard to see where you are when measuring
to the base of the neck.

An example would be the 300 Win Mag(Short neck) and a 30/338(long neck)
so when compairing cartridges it,s the most consistent.

Obviously you cant use the volume of the neck but when you see a volume
of a case reported buy a manufacture it is measured this way because if you
seat the same bullet to the same max COAL it will tell you the difference
between two different cartriges.

I hope this answered your question.

J E CUSTOM

 

[RockyMtnMT]

J E Custom,

That does answer my ? thank you.

Steve

 

[Mikecr]

I'll tell you how I do it, cuz maybe it'll help.

Fully fireform the cases
Deprime(do not size)
Tumble as usual
Stand each case on a scale using a plastic golf tee inserted into the flash hole
Zero scale
Add water to case with an eyedropper to the mouth. To do this consistantly, I've added a few drops alcohol to a cereal bowl of water, and I touch a tissue corner to any meniscus formed at the mouth.
Subtract weight of tee & record my measurement
Dump water and set case in tray to dry

It's a comparative measurement for me with the cases fully prepped including trimming. If you don't zero scale, but instead, record dry case weight, you may find that case weight doesn't correlate with h20 capacity.
It depends on the cartridge/brass quality/lot.
I haven't run into unexpected differences from QuickLoad or from 'Cartridge Designer' in RCBS Load from a Disk.
I believe their capacities are based on a full case(to the mouths), and that makes sense as there is no standard seating depth with any standard bullet.

 

[jwp475]

I have a book that contains the water capacity of most cartridges (wilcats & factory) I can look up any that any one is interested in, it even list the amount of capacity taken up by the bullet when seated.

 

[RockyMtnMT]

jwp475,

Try the 30-338lap imp 40deg shoulder.

Steve

 

[Mikecr]

What is it you're going to do with case capacity?

 

[jwp475]

The listing that I have is for the 338 Lapua necked down to 30 caliber and that case holds 156 grains of water. A 30 caliber bullet seated displaces 18.84 grains of water per inch and this should work for any case in 30 caliber.

 

[RockyMtnMT]

What is it you're going to do with case capacity?

I need to send the water capacity of a fired, un-sized case to send to GS Custom bullets.
They have some new bullets that have gone through field testing, but not on their site yet, that Gerrard told me may work for what I've got. If not, then to get start loads, and expected velocities for their 173grn HV bullet.