Three Winchester .243 cases with water to the neck and shoulder junction held 53, 52.3 and 52.7 grains of water.

Three Winchester .243 AI cases (same lot) held 54.7, 54.6 and 55 grains of water.

Note the regular .243 cases had been once fired and neck sized so their internal capacity was a tad more than if they had been FL sized down to factory ammo specs.

Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!