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?
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!
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.