Is the military need of the United States for Japanese silk a controlling factor in withholding a total embargo on Japanese imports? From time to time, this question has been a matter of discussion when the subject of strategic raw materials has been under consideration, writes Capt, Frederick L, Oliver in the "Christian Science Monitor." In so far as the United States Navy' is concerned silk is a strategic raw materia] that is extensively used for powder bags and parachutes. Not necessarily Japanese silk, but inasmuch as Chinese and Italian silks are at present unavailable. Japan now affords the only large source of supply.
All modern breech-loading guns fall into two general classes—the case gun and he bag gun. "The case gun uses what is known as fixed ammunition in which the power) shell, vase. and primer are assembled into what the layman would recognize as a cartridge. The bag gun uses what is termed separate ammunition. As may be gathered from this term. the shell and the powder are inserted separately into the chamber of the gun. the powder being contained in a strong silk bag of a diameter and length appropriate for the calibre of the gun with which it is used.
Silk is used for this purpose because it is more completely burned when the gun is fired than is any other material having the necessary strength for use as a powder bag. Before silk came into use for this purpose, woollen bags were used, because the unconsumed particles of that materia] had little tendency to smoulder. It could not be trusted, however, and the bore of the gun had to be swabbed with water after every round. The rapidity with which modern guns are fired precludes the loss of time entailed by this operation.
With the case gun, the powder of a succeeding charge is not exposed to embers remaining in the powder chamber of the gun, but with the bag gun the opposite holds true, and constitutes a grave danger to the gun crew. In fact, the Navy has, in the past, experienced a number of serious accidents occasioned by powder charges having been ignited in such a manner. To prevent the possibility of incompletely consumed particles of burning silk or powder remaining in the powder chamber. all bag guns in the United States Navy are fitted with a device which admits high pressure air into the chamber of the gun just as the breech-block opens. This operates to blow all embers through the muzzle of the gun.
In addition, all turrets are air tight, and while firing is in progress, are maintained under a slight air pressure which serves to send a supplementary current of air through the bore of the gun when the breech is opened. These improvements make it possible to use material other than silk for powder bags, but as long as the latter is available its use is preferred.
Text read from the printed page and cleaned; old type leaves the occasional error.