How much heavier a 9.2-inch cruiser shell was

How much larger would the shell be for a 9.2-inch-armed County-class cruiser?

Roughly fifty percent heavier than a representative 8-inch shell, about 380 pounds versus 256 pounds.

The comparison uses the 9.2-inch Mark XI gun associated with Agamemnon and the 8-inch Mark VIII. Their cited shell weights are about 380 pounds and 256 pounds respectively. That gives a difference of roughly 124 pounds. The 9.2-inch projectile is therefore described as about fifty percent heavier.