Projectiles
The Paris Gun shells weighed 94 kg (210 lb); the shells initially used had a diameter of 211 mm (8.3 in) and a length of 105 cm (41 in). The main body of the shell was composed of massively thick steel, containing around 15 kg (33 lb) of explosiveThe small amount of explosive – 15% of the weight of the shell – meant that the effect of its shellburst was considered small for the shell's size. The abnormal thickness of the shell casing, to withstand the massive forces of firing, meant that shells would explode into a comparatively small number of large fragments, limiting their destructive effect. A crater produced by a shell falling in the Tuileries Garden was described by an eye–witness as being 10 to 12 ft (3.0 to 3.7 m) across and 4 ft (1.2 m) deep.
The shells were propelled at such a high velocity that each successive shot wore away a considerable amount of steel from the rifled bore. Each shell was sequentially numbered according to its increasing diameter, and had to be fired in numeric order, lest the projectile lodge in the bore, and the gun explode. Also, when the shell was rammed into the gun, the chamber was precisely measured to determine the difference in its length: a few inches off would cause a great variance in the velocity, and with it, the range. Then, with the variance determined, the additional quantity of propellant was calculated, and its measure taken from a special car and added to the regular charge. After 65 rounds had been fired, each of progressively larger caliber to allow for wear, the barrel was sent back to Krupp and rebored to a caliber of 238 mm (9.4 in) with a new set of shells.
The shell's explosive was contained in two compartments, separated by a wall. This strengthened the shell and supported the explosive charge under the acceleration of firing. One of the shell's two fuses was mounted in the wall, with the other in the base of the shell. The shell's nose was fitted with a streamlined, lightweight, ballistic cap – a highly unusual feature for the time – and the side had grooves that engaged with the rifling of the gun barrel, spinning the shell as it was fired so its flight was stable. Two copper driving bands provided a gas-tight seal against the gun barrel during firing.
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