From the News

Dated: December 21, 1916

The life of a gun depends upon the progress of erosion, which sooner or later is certain to impair the accuracy of fire. Erosion is caused by the action of the explosive gases at high temperature and pressure. The hot gases cause a thin film of steel to absorb heat. The film expands and becomes set. On the release of the pressure it contracts, which causes minute cracks that grow larger with every shot fired. Thus they form passageways for more hot gas and that tends to enlarge them still further. The inner surface thus becomes roughened and the bore begins to corrode. Finally the bore becomes so enlarged that it allows the gases to escape. The shell does not then acquire its proper rotation and his flight becomes erratic. All guns except small ones are now constructed with linings in the tube, which, when the bores is worn out, are removed and replaced by new ones. The cost of relining a gun is approximately 30% the cost of the gun. There appears to be no limit to the number of times that a gun can be relined. Small arms used in this country are considered to be worn out after 5000 to 7500 rounds have been fired. Small naval guns can be fired about 1000 times before they are regarded as worn out. Large 12 inch and 14 inch naval guns are considered to have a life on one lining, of not more than 150 rounds. Low velocity guns, such as howitzers and mortars, have correspondingly longer lives than high velocity guns of the same caliber, because the pressure they developed is less, and hence the temperatures are lower.