The Works Of Messrs. Schneider And Co.

GONCENTRIC-THREADED BREECH-BLOCKS. 213 the gun. In this way, as soon as the closing motion of the breech is commenced, and during this motion, the cam will act on the stock of the striker, dr i ving; it back and bendine- its spring. To fire the fuse, it will suffice to displace the lever catch slightly, thus setting the striker free. Prématuré firing is impossible in both cases, for as soon as the handle of the lever is started to open the breech, the heel of the inside rod engages a projection on the right- hand brauch of the striker, and prevents all forward motion of the latter. Figs. 727 and 728 show the type of firing mechanism; whilst Figs. 723 to 726, repröduced from photo- graphs, show the breech-block in the open and closed posi- tions ; the example illustrating this breech-block belongs to a 47-millimetre (1.850 in.) gun, 60 calibres in lengtli, of high power. Several series of tliese have been manufac- tured for various Governments and for the French Navy. Concentric Threaded Breech-Block for io-Centi- metre (3.937-in.) Quick-Firing Gun (Figs. 727 and 728). however, turns round a vertical axis ; owing to this arrangement, the weight of the block does not cause much ineonvenience, and tlie efforts required for working the mechanism are not excessive, or beyond the manual power of the men. The type seleeted for description is fitted with intermediate transmission, though in most cases this can be dispensée! with. The vertical axis round which the block turns corre- sponds with the centre of the gun ; consequently, the con- centric threads and their depths in the breech are in parallel horizontal planes. When the breech is open the breech-block forms a lip, which facilitâtes charging the gun. At the top part is fitted a segment of a pinion that engages a similar pinion keyecl on a horizontal shaft, turn- ing in two bearings at the rear end of the m, The working crank, on the left-liand side, is keyed on this shaft, by means of which the shaft is opened and closed. The accessory parts—firing device, safety arrangements, locking Concentric-Tlireaded Breech-Block for 10-Centimetre Gun. —These are views of a breech-block of this type, fitted to a 10-centimetre (3.937-in.) quick-firing gun of high power. The working parts and firing mechanism are similar to those for the 47-millimetre (1.850-in.) guns above described. The catch lever, however, is not fitted with a tooth, but the cylindrical axis of the working crank is provided in the part inside the breech-block mortice with a bevel-shaped stop catch. One of the concentric threads is also bevelled, so that at the end of the travel of the catch lever, the cam is driven to the lef't, and frees the striker as previously described. Numerous other examples could be given of concentric- threaded breech-blocks, for small and medium-calibre guns, which differ from the above only in the accessory gear, and especially in that of the firing device. A few words should, however, be added with reference to the manner in which the concentric screw has been applied to the breech mechanism of large-calibre guns. Concentric-Threaded Breech-Blocks for Large- Calibre Guns (Fig. 729, a, b, c).—The same principle has been adaptec! to large-calibre guns. The breech-block, gear—are of the same type as those previously referred to. Several other examples could be described, but this one will give an exact idea of the remarkable qualities of this new type of breech-block. The advantages claimed for the concentric-threaded system are the following : 1. Extremely rapid manipulation. 2. Complété éjection of the cartridge-cases. 3. Absolute safety against prématuré firing, accidentai opening, or hanging tire. 4. Facility in taking apart and refitting the breech- block and mechanism. 5. Easy inspection of the threads and of other wearing parts. 6. Utilising the block itself as a charging table. 7. Removal of all risk of wedging and shearing, should the case not be placed quite home in the chamber. 8. Fewness and simplicity of parts, and their complété protection in ail positions. 9. The use of cartridge-cases with a concave bottom, which reduces risks of accidentai explosion during handling.