Case Capacity from Water Weight
Weigh an empty case, then fill it with water and weigh again — this converts the difference into grains and cc.
How this works
Filling an empty, primed (or de-primed and plugged) case with water and weighing the difference against the empty case gives an extremely precise measurement of the actual internal volume — far more reliable than any published spec, since real cases vary by brand, lot, and even how many times they've been fired and resized.
Why this matters for load density and pressure
Case capacity feeds directly into the Load Density calculator, and knowing your actual case volume (rather than an assumed generic one) makes that load-density number meaningfully more accurate — useful context when comparing loads across different brass brands that may hold noticeably different powder volumes at the same charge weight.
Frequently asked questions
Why measure with water instead of trusting a published spec?
Real case capacity varies measurably between manufacturers and even between lots from the same manufacturer — a direct water-weight measurement of your specific brass is far more reliable than any generic published figure.
Does case capacity change as brass is fired and resized multiple times?
It can shift slightly over the life of a case due to brass flow, which is one more reason to measure your actual current brass rather than relying on a one-time factory number.
How does this feed into the Load Density calculator?
The grains-of-water result here is exactly the case capacity input that calculator needs, so measuring your case capacity first makes your load density number meaningfully more accurate.
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