Breech-Loader, Model 1864-67.
These guns are hooped like the model of 1870, but are not tubed.
14-cm. French Gun.
The vent is pierced vertically near the bottom of the powder-chamber, instead of being in the breech-block.
The grooves are of the pattern known as the “basket-handle,” for mechanical fit projectiles ([see French Groove, English Ordnance]), having an increasing twist of from 0° to 6°. The 14-cm. and 16-cm. guns have three grooves, the others five. The width of the grooves is the same throughout the length of the bore, being cut back on the loading side near the powder-chamber to facilitate loading. The depth of the groove, however, diminishes towards the muzzle in order to pinch the studs and steady the projectile. At the powder-chamber and running forward for a short distance in the centre of each band is a supplementary groove, in which travel the rear studs of the projectiles, which are made so small as to easily sheer off. These secondary grooves prevent the projectile from being pushed too far into the bore. With the 19-cm. gun, the supplementary groove is made by cutting back the loading side of the regular groove. There is no shot-chamber proper.
Groove (1864).
Groove (1871).