Well. I don't have a case, but I do have a couple of numbers that might help. The weight of a solid brass case would be 1131 grains (custom cartridges). Subtract the weight of your primed case from 1131, to get the weight of your case volume in brass. Multiply that number by .1176 to convert to water weight.
Thanks for that formula but I don't actually have a case. Normally I take a case, fill it to the top, and pour it out into the pan and weigh it. I am just trying to figure out the case capacity for my next project. Good shooting.
If this helps, my accuracy load in the 300 Weatherby case is 75.5 to 77 grs of RL22 or 80 grs of H1000 with 220 gr bullets. My hunting load if I'm using 200 gr MK bullets is 90 grs of H870 or 90 with the WC872. All above with at least 30" barrels.
As you know, most shooters at Williamsport are above the pressure standards that are published in the loading manuals. It's a trial and error situation sometimes because nothing is printed with the LONG barrels in mind.
Most of the loading publications are printed "low" as to protect the publisher and manufacturer from liability by someone who has weak or faulty equipment.