SYNOPSIS:- The principal causes of erosion in the gun-barrel bore are cracks awl the deterioration caused by the action of the gun-powder gas, as well as abrasion due to projectiles passing through. The author investigated microspically and by X-rays the cracks and the characteristiclayer on the eroded surface of the bore. It was ascertained that the characteristic layer has a structure which has become martensitic due to the heating effect of the gun-powder gas. At theinstant of discharge, the

more »

... barrel. expands and contracts, and also the hard layer itself does so due to the beating effect of the gun-powder gas, so that innumerable number of cracks occurs on that layer by repetition of such actions. The gunpowder gas penetrates through these cracks, and accelerates the erosion. Thus it was concluded that the action of the gun-powder gas is the fatal cause of the deformation of the bore by erosion.