Glossary of British ordnance terms
This article explains terms used for the British Armed Forces' ordnance and ammunition. The terms may have different meanings depending on their usage in another country's military.
BD
Between decks: applies to a naval gun mounting in which part of the rotating mass is below the deck, and part of it is above the deck. This allows for a lower profile for a turret, meaning that the turrets need not be superfiring.[|BL]
The term BL, in its general sense, stood for breech loading, and contrasted with muzzle loading. The shell was loaded via the breech followed by the propellant [|charge], and the breech mechanism was closed to seal the chamber.Breech loading, in its formal British ordnance sense, served to identify the gun as the type of rifled breechloading gun for which the powder charge was loaded in a silk or cloth bag and the breech mechanism was responsible for "obturation" i.e. sealing the chamber to prevent escape of the propellant gases. The term BL was first used to refer to the Armstrong breechloaders, introduced in 1859. Following the discontinuation of Armstrong breechloaders and the period of British rifled muzzle-loaders [|RML], British breechloaders were re-introduced in 1880. At this point the term rifled breech-loaders [|RBL] was retrospectively introduced to refer to the Armstrong breechloaders, which had a totally different breech mechanism, and since then the term breech-loaders BL has applied exclusively to the type of breechloader introduced from 1880 onwards, using an interrupted-screw breeches.
Early British Elswick breechloaders in the 1880s used a steel "cup" obturation method. This was quickly superseded in guns designed by the Royal Gun Factory by the French de Bange method, the basic principle of which is still in use today. In British service this became a Crossley pad with an interrupted thread screw block e.g. a Welin screw. The shell was loaded via the breech, followed by the propellant charge in a cloth bag. A single-use "vent sealing tube", a type of primer not dissimilar in appearance to a blank rifle [|round], was inserted into the breech for firing the gun.
While originally, the term "BL" contrasted with "ML", or "muzzleloader" guns, after muzzleloaders were discontinued, the term came to distinguish between traditional, non-obturating guns with fabric propellant bags and separately loaded shells, and quick-firing [|QF] guns which used self-sealing brass cartridge cases, and which usually had the propellant and projectile fixed together as a unit for faster handling and loading. For instance, Britain before World War I had both QF and BL guns. Both were "breech loading" in the general sense, but in the formal nomenclature it separated guns with breeches designed for charges in brass cartridge cases for quick-firing QF from those designed for cloth bag charges for breech-loaders BL.
Shells designed for one type were not necessarily suitable for use in the other type; for instance, a BL shell relied upon the tight fit of its driving band in the gun bore to prevent it slipping back when the gun was elevated, but a QF shell could rely upon the cartridge case, either fixed or separate, to prevent it slipping back. This presented difficulties for BL guns at high angles. A special cartridge was developed for BL guns on HA mountings, with provision for a wooden stick to be inserted through the centre to prevent the shell slipping back on elevation.
Although fixed ammunition allows for a rapid rate of fire in small to medium guns, BL is a better choice for heavy calibre guns; propellant was loaded in a number of small fabric bags, because a single bag holding the full charge would be far too big and bulky for the handlers to lift. Using fabric allows for the charge to be broken into small, easily handled units, while it would be difficult to design a system by which multiple small metallic-cased charges were loaded and fired at the same time. Using multiple small fabric bags also allows the gunners to use a reduced charge if need be.
BLC
The term "BLC" stood for "BL converted" and referred to a breech and breech mechanism modified from an early long-screw three- or four-motion to modern short-screw single-motion. An example is the conversion of the BL 15-pounder to BLC 15-pounder.C.R.H.
Calibre radius head: the radius of a circle with the curve of the shell's nose on its circumference, expressed in terms of the shell's calibre. The longer and more pointed the shell's nose, the higher the C.R.H. Typical C.R.H. for British shells leading up to World War I was two: e.g. the curve of the nose of a two C.R.H. shell was equivalent to the curve of a circle with a radius of. Shells of four C.R.H. were soon developed in World War I, identified by an A following the shell mark number, B for six, and so on. For modern streamlined shells post-World War I, two numbers were necessary to more correctly denote a shell's C.R.H. characteristics. For instance, the World War I 6-inch 26 cwt howitzer shell was two C.R.H., and the World War II Mk 2D shell was referred to as "5/10 C.R.H.".Cartridge
"Cartridge" in British ammunition terminology typically refers to the physical object containing the propellant that a gunner loads.For small arms and [|fixed QF] artillery ammunition, e.g., the.303 or 18-pounder respectively, this denoted the complete round, that is, the cartridge case, percussion cap or primer, propellant charge and projectile. In this use it is synonymous with "round".
For [|separate QF] artillery, cartridge referred to the cartridge case, its primer, propellant charge, and the disposable lid and fastener of the case.
In BL artillery terminology, cartridge referred to the propellant unit only – there was no case. British cartridges contained [|gunpowder] until about 1892, and thereafter sticks of cordite bound together with an igniter pad, if necessary, in a cloth bag, usually silk. The "stick" nature of cordite gave the cartridges a degree of rigidity and hence they retained a tubular shape and could be handled and loaded as a solid unit even without a case. With BL, cordite is contained in one or more cloth bags joined together. The complete unit is termed a cartridge. The empty bag was termed an "empty cartridge". Heavy naval guns may require up to four separate cartridges to be loaded, each consisting of a charge, to make up the full service charge.
Howitzer cartridges, both BL and separate QF, contained a central core of cordite surrounded by several stacked ring-shaped bags of cordite. To obtain the appropriate "charge" for the required range and angle of elevation, the gunner discarded one or more rings before loading.
See charge for how Ordnance QF 25-pounder charges varied in World War II.
Cartridge case
The case, usually brass, holding the propellant charge. Used with small arms and QF artillery ammunition. The QF cases in 1915 could be cleaned and then reloaded up to a maximum of six firings with Cordite charges, with the record detailing the "life of the case" marked on the base. The limitation on the number of firings was due to the case expanding on firing, having to be "rectified" by turning metal off the lower part, which restored the correct dimensions but progressively weakened the case.Charge
Charge was a concept or category label rather than a specific item. It can be described as "the standard amount of propellant specified to carry out a particular purpose":- Full service charge: the full amount of propellant intended for use in action at maximum range, for the usual shell. If a gun had e.g. a "heavy" and a "light" shell, there would be a separate charge associated with the heavy and light shells.
- Reduced service charge: for practice or firing star shells.
- Proof charge: a charge giving 25% greater chamber pressure than the full service charge, intended only for the "proof" or testing of a gun.
- Blank charge: intended for firing without a projectile, usually a reduced charge.
- Battering charge: a specially large charge for use with "Palliser" projectiles, which were an early British armour-piercing projectile of the mid-to-late 19th century.
A howitzer gunner's job was more complicated because the range table would specify different "charges", or fractions of the full service charge, for different ranges and angles of shell descent. The standard cartridge for his gun, which as a whole made up the full service charge, would consist of a central "mushroom" cordite core and several smaller cordite rings in bags stacked around the core like doughnuts, all tied together. It was designed so that one or more rings could be quickly removed and discarded before loading, hence providing progressively smaller charges. E.g. if the gunner on a QF 4.5-inch howitzer was ordered to load charge four, he would know he had to remove the top ring from the cartridge, leaving four rings; for charge three he would remove two rings. Discarded rings were burned after the action. This was the standard procedure for howitzers up to and including World War II.
In World War II a different system was introduced for varying charges for the QF 25 pounder gun-howitzer, which used separate-loading QF ammunition. A separate "super charge" cartridge was available for firing the high-velocity anti-tank AP shot, and an additional "super charge increment" could be added to that for even higher velocity. The cartridge for firing the standard shell came ready-loaded with a red bag at the bottom containing the basic charge, together with white and blue bags laid lengthwise, as in a conventional gun charge, to make up the full service charge. The blue and white bags could be removed to provide progressively reduced charges. From 1944 one or two "intermediate charge increments" could be added to the standard charge for high-angle fire and to provide greater control over angle of shell descent.
For small arms or fixed QF ammunition, where the charge could not be varied by the gunner, the term charge was used to identify the Cordite propellant within the cartridge case, and the round as a whole was referred to as a full or reduced charge. E.g. an 18-pounder star round consisted of a cartridge case containing a reduced charge, and an attached star shell.