entirely of steel, except for the brass bushings used for the elevating and cross-leveling screws. A US M4 sight may be fitted to the Japanese weapon by shimming the sight bracket slightly. The Type 97 mortar examined had an extension fitted to the sight, raising the latter to the level of the muzzle of the mortar. This extension probably was added to permit sighting of the weapon when it was deeply dug in or slightly in defilade. Elevation scale of the sight is graduated in 50-mil intervals from 700 to 1,600 mils, and a micrometer drum enables elevation readings to be made to the nearest mil. The collimator can be traversed in a full circle, and the azimuth scale is calibrated in 100-mil graduations in two sections of 3,200 mils each. As in the case of elevation, a micrometer drum permits azimuth readings to be made to the nearest mil. There is a throw-out lever for rapid traverse of the collimator, which may be placed at an angle of elevation and locked in position by a series of meshing notches. There are no open sights for rough laying of the piece. Ammunition Ammunition recovered for the Type 97 thus far is usually the Type 00 (1940) HE shell. This shell is long and weighs , of which is the weight of the TNT filler. The fuze is of the instantaneous type, which can be set for delay action, however, by the insertion of a delay pellet in the fuze nose prior to firing. The shell could be fired in the US 81-mm mortar M1, but the range was about 10 per cent shorter than achieved with the US M43 and M43A shells. The 81mm mortar was also used to launch an unusual AA Mine Discharger shell. Specifications Specifications of the weapon are as follows: References Notes Bibliography War Department Special Series No 30 Japanese Mortars and Grenade Dischargers 1945 War Department Handbook on Japanese Military Forces 1 October 1944 External links War Department TM-E 30-480 Handbook on Japanese Military Forces at hyperwar.org A Type 100 81mm mortar round at inert-ord.net World War II infantry weapons of Japan Infantry mortars of Japan 9 81mm mortars Military equipment introduced in the 1930s