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.
In the Royal Navy charges were known as either "Full" or "Practice" charges, the designation depending on the number of cordite cartridges used. The practice charge for calibres of 7.5-inch and above was a "three-quarter charge", except for Marks III to VII of 9.2-inch were it is a "half-charge".
- Gunnery Drill Book, Book I, 1913. p. 626.
- Admiralty, Gunnery Branch (1913). Gunnery Drill Book for His Majesty's Fleet. (Book I.) (Instructions for Power-Worked Mountings). London: Eyre and Spottiswoode, Ltd..