
121Ammunition Design Practice
not stick in the chamber. When a xed round of ammunition is loaded into the chamber, the
rear face of the tube provides the stop and seat for the rim of the case. During the expansion
of the pressurized case, the forcing cone of the chamber forms the seal for the hot gases by the
extrusion and engraving of the rotating band in a ried bore or the extrusion of the obturating
band in a smooth bore. The ratio D
c
/D is known as the chambrage, an important characteristic
of the design. Large values of the chambrage tend to cause turbulent ow of the gases as they
enter the bore. Such turbulence contributes to the erosion ...