Originally Posted by Swamplord
The case water capacity is a typo in the above diagram, it's more like 105 gr. water....
As the owner of AmmoGuide, I can assure you that the 102.9 gr. Case Capacity listed in the AmmoGuide data is NOT a typo.
First, understand that water is extremely dense and it doesn't take much of it to make the 2 grains difference you perceive (about 2% of the total volume in your wildcat's case, actually).
Secondly, 2% (the difference between 105 and 102.9) is an acceptable tolerance for even high-precision instrumentation. In my Navy days as a Nuclear Electronics Technician, the multimeters we used to measure/calibrate voltages of systems directly affecting the reactor core
only had to be within 3%.
Thirdly, "case capacity" is a particularly elusive parameter to nail because it is subject to many real-world variables when being measured. Any 2 people trying to measure it are unlikely to come up with the same answer. The temperature of the air & water, altitude, how many times the case has been reloaded, whether the case is clean inside, whether the case has been fired, resized or even HOW it was resized... these and even more factors cause "case capacity" to vary when measured empirically. You may consider "105" to be THE NUMBER but the relevance of your result to the rest of the world is reduced because of this variability.
Plus, since you shoot a wildcat, your cases are certain to have been fired at least once and/or formed in a die before measuring. There is no such thing as a "factory virgin" case in 6.5 PRO - your volume measurement will alwys be affected (slightly) by the specifics of either your rifle's chamber, die size or both.
AmmoGuide calculates the internal volume of the case in grains of water in a uniform manner that assumes virgin, unsized, unfired brass. Therefore, the website's values are much
more useful in terms of comparison with other case capacity values on the website because all variables have been removed
in the estimates for all cases.