AUTOMATIC PISTOLS Such weapons are now numerous and vary greatly in design, with calibres ranging from •455 to .250 inches. In all cases, however, their operation is dependent on the result of firing a round. If the base of the cartridge be not supported in the chamber when it is exploded, it will be blown to the rear, the gas will escape, the bullet will not be projected, and the firer will also probably suffer.
Automatic Pistols can be divided into two main types, i.e., (a) Those in which the barrel and bolt are positively locked to gether till the bullet's exit. (b) Those dependent on inertia with no mechanical locking. The latter, for sealing the breech, rely on the weight of the moving parts which place the round in the chamber, and which hold it there by the assistance of strong springs, together with the friction on extraction caused by the cartridge case expanding under the explosion and gripping the walls of the chamber.' The small bore pocket pistols are frequently of type (b). However, in view of the requirements of a revolver or pistol, previously referred to, type (a), which permit of a heavy bullet and a heavy charge, are usually the most employed for military purposes. There are two sub-divisions of type (a) namely, (I) Those in which the barrel and bolt recoil together in the same plane for a short distance prior to unlocking. (Luger Parabellum, Mauser [Germany], Frommer.) (2) A lowering movement of the barrel during recoil, which unlocks itself from the bolt after a short distance.' (Webley & Scott, Colt.) The Luger functions on somewhat similar lines to the Maxim or Vickers Machine Gun. In it the bolt is supported by a tog gle joint, the centre hinge of which is below the level of the ones on either side of it and bears against the metal of the frame. Locked in this way, barrel and bolt recoil together until the centre hinge meets a ramp and is forced upwards so breaking the joint and knuckling the bolt back against the compression of a spring.
Not quite similar to (I) and (2) above, is a third form of barrel movement, i.e., a turning motion of the barrel during recoil, thus bringing about unlocking. (Steyr and Savage.)
Of type (b) a Browning 9mm. Military Model, manufactured in Belgium and marked F.N. (Fabrique National) is the weapon of Belgium, Holland and of some S. American States.
Owing to the similarity in outward appearance between vari ous automatic pistols, not much can be learnt from photographs. However, on this page are diagrammatical sketches of the prin ciples employed in some of the locking actions mentioned above.
Holding-open devices are embodied in most automatic pis tols, and warn the user that the magazine is empty. The maga zine platforms, or levers operated by them, rise when the maga zine is empty and hold back the recoiling parts, thus putting the pistol temporarily out of action.
A danger common to most automatic pistols is that when the magazine is removed a live round is usually left in the chamber, and, if forgotten, may result in an accident. Hammerless pistols give no indication as to whether the pistol is cocked or not. On the other hand, with hammers projecting at the rear of the pistol there is a possibility of cocking the hammer by an accidental knock or by friction.
There is only one well known sample of a semi-automatic revolver, namely, the Webley Fosbery .45. In it is the usual six chambered cylinder. When the round is fired, the cylinder and barrel recoil and in so doing the cylinder is made to turn half the distance necessary for aligning of the next chamber with the hammer. After recoil a strong spring forces the recoiling por tions forward and the cylinder rotates through the remaining necessary distance. (H. R. A.)