Tubes and primers for ammunition

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In ancient times various devices were adopted to ignite the charge. Small guns were fired by priming powder poured down the touch hole (or vent) and ignited by glowing embers or a red-hot iron rod. Later the priming powder was ignited by a piece of slow match held in a linstock (a stick with a clamp at one end). About 1700, this was effected by means of a port-fire. This was a paper case about 16 inch (406 mm) long filled with slow-burning composition which burnt rather more than one inch (25 mm) per minute. Later again the charge was exploded by paper tubes (sometimes called Dutch tubes) filled with powder and placed in the vent and ignited by a port-fire. In comparatively modern times friction tubes have been used, while in the latest patterns percussion or electric tubes are employed.

Vent sealing tubes[edit]

In most breech loading guns it is essential to stop the erosion of the metal of the vent by preventing the escape of gas through it when the gun is fired. For this purpose the charges in such guns are ignited by "vent-sealing tubes." For muzzle loaded guns and small breech loading guns radially vented, especially those using black powder, the amount of erosion in the vent is not so serious. The charge is fired by ordinary friction tubes, which are blown away by the escape of gas through the vent. In all guns axially vented, vent-sealing tubes, which are not blown out, must be employed to protect the gunners from injury. This 'vent sealing' name remained part of British nomenclature, rather than a clearer name of 'primer' or 'firing' tubes, as used elesewhere.

Friction T-tube, British Mk IV of 1914

The common friction tube is a copper tube, packed with powder, having at the upper end a short branch (called a nib piece) at right angles. This branch is filled with friction composition in which a friction bar is embedded. When the friction bar is sharply pulled out, by means of a lanyard, the composition is ignited and sets fire to the powder in the long tube; the flash is conveyed through the vent and ignites the gun charge. For naval purposes, to prevent the sailors from being cut on the face or hurting their feet, tubes of quill instead of copper were used. If friction tubes are employed when cordite or other smokeless powder charges are used, the erosion of the vent is very rapid unless the escape of the gas is prevented; in this case T-headed tubes are used. They are similar in action to the ordinary type, but are fixed to the vent by the head fitting a bayonet joint formed with the vent. The explosion blows a small ball upwards and blocks the coned hole at the top of the tube and so prevents any rush of gas.

To provide a higher rate of fire, the last pull-lanyard friction T tubes in British service were replaced from 1907 in the converted 15pdr with a 'push' T tube, using an impact detonating compound, in a new axial vent.


Electric tubes[edit]

In the English service electric tubes (in the United States called "primers") are mostly used, but percussion or friction tubes are preferred on the continent and electric tubes are seldom or never used.

There are two types of electric tube, one with long wires for joining up with the electric circuit and the other without external wires. The first type has two insulated wires led into the interior and attached to two insulated brass cones which are connected by a wire "bridge" of platinum silver. This bridge is surrounded by a priming composition of guncotton dust and mealed powder and the remainder of the tube is filled with powder. When an electric current passes through, the bridge is heated to incandescence and ignites the priming composition.


Percussion tubes[edit]

Percussion cap nipples; the ignition flame travels though the hole
Percussion caps





The first cartridges for cannon were made up of gunpowder packed in a paper bag or case. For many years after the introduction of cannon the powder was introduced into the bore by means of a scoop-shaped ladle fixed to the end of a long stave. The ladle was made of the same diameter as the shot, and it had a definite length so that it was filled once for the charging of small guns but for larger guns the ladle had to be filled two or even three times. The rule was to make the powder charge the same weight as that of the shot.




All smokeless powders are somewhat difficult to ignite in a gun, so that in order to prevent hang-fires every cartridge has a primer or igniter, of ordinary fine grain gunpowder, placed so as to intercept the flash from the tube; the outside of the bag containing this igniter is made of shalloon, to allow the flash to penetrate with ease. The charge for heavy guns i.e. above 6 inches (150 mm), is made up in separate cartridges containing half or quarter charges, both for convenience of handling, and to allow a reduced charge to be used.


For quick-firing guns the charge is contained in a brass case to which is fitted a primer for igniting the charge. This case is inserted into the gun, and when fired slightly expands and tightly fits the chamber of the gun, thus acting as an obturator and preventing any escape of gas from the breech. This class of ammunition is especially useful for the smaller calibres of guns, such as 3-pounder (1.4 kg), 6-pounder (2.7 kg) and field guns, but Messrs. Krupp also employ metallic cartridge cases for the largest type of gun, probably on account of the known difficulty of ensuring trustworthy obturation by any other means practicable with sliding wedge guns.

The charges for these cases are made up in a very similar manner to those already described for breech loading. Where necessary, distance pieces formed of papier-mâché tubes and felt wads are used to fill up the space in the case to prevent any movement of the charge. The mouth of the case is closed either by the base end of the projectile, in which case it is called "fixed ammunition" or "simultaneous loading ammunition" or by a metallic cap, when it is called "separate loading ammunition," projectile and charge being thus loaded by separate operations.

See also[edit]