A Firing Charge is the propellant load used to fire a shell from a gun.
Some guns had fixed ammunition with an integral charge. Larger guns typically had separate powder bags loaded behind the projectile, and the gun supported more than a single configuration of charging. It was common, for instance, to use a gun in practice firings with fewer bags.
- Full Charge firing typically meant using all the bags that could be loaded (usually 2, 3 or 4 bags)
- 3/4 Charge meant leaving 1 bag out of a gun whose full charge was 4 bags
- 2/3 Charge meant leaving 1 bag out of a gun whose full charge was 3 bags
- Reduced Charge usually meant leaving 1 (or 2?) bags out.
Using less than a full charge would be done to minimise wear on the bore of the barrel, or (rarely) to achieve steeper angles of fall, perhaps to mimic longer-range fire or challenge an enemy's horizontal protection.
Just as was generally the case when switching projectiles, using alternative charges necessitated swapping out cams in gun sights and elsewhere to reflect the different ballistic properties.