Mortar Fuzes
This article is from TM 9-1904 which is available on this site.
The contents have been supplemented with modern photos and comments or additional information added in some instances.
Date Compiled: 7/17/2007
Editor: Chris Guska
General. The fuses used with the 81-mm and the 60-mm mortar ammunition are, except for the 60-mm illuminating shell, of the point detonating type. The stability of the shell in flight allows the use of this type of fuse. The M45 Fuse, first used on the M43, M44 and M45 Shells, is a point-detonating fuse having a selective feature which allows the fuse to be set for either super quick or delay action as desired. The super quick action is used for effect against light targets above the ground where no penetration is necessary, and a fragmentation effect is desired such as against personnel and barbed wire entanglements. The delay action is used against heavy targets and underground structures where penetration is desired to produce the most effective mining and concussion results.
Recently it was decided that each shell could be classified as for use against light targets or as for use against heavy targets. Thus, a single action fuse could be definitely assigned to each shell according to its tactical use. All of the light shell (7 pounds or less) were classified for use against light targets, as very little penetration could be obtained due to their light weight and blunt construction. It is also to be noted that the percentage of explosive filler as compared to the percentage of metal components (approx. 17 percent) was designed to destroy the light shell so as to produce efficient fragments which can be effective only if distributed above ground. The M52 P.D.Superquick Fuse was also assigned to the Chemical Shell M57, as it is necessary to function the chemical shell above the ground to obtain the proper effects and dispersion to its chemical filler. All the heavy shell of the H.E. type were classified for use against heavy targets and for use where a mining effect was necessary. It is also to be noted here that the percentage of explosive filler as compared to the percentage of metal components (approx. 40 percent) was designed to produce an efficient mining or concussion result with heavy shell which would be most effective if allowed to penetrate its target and then explode. The M53 P.D. Delay Action Fuse was assigned to this shell.
The M45 P.D. Selective Fuse was declared limited standard (S). It was a waste of one element to use a selective fuse on trench mortar shell, because it was known before the shell ever reached the firing point what action fuse was desired. The M52 P.D. super quick-and the M53 P.D. delay are standard for issue and manufacture (S as M). It is interesting to note that the subdivision of a selective fuse into two separate fuses is in definite opposition to the trend in artillery fuse design where the tendency is to combine two fuses into one selective or combination fuse. This is true because in artillery fuses the action desired varies with the condition at the field of battle.
Rounds used with these fuses may be considered bore safe. The detonating elements are positively separated from the booster until the projectile has left the bore of the mortar. The fuses are assembled to their respective shell and stacked in place; they are, therefore, being stored, shipped, and issued as a permanent part of the complete round. Each fuse is stamped with its model number, manufacturer's initials, and lot number for positive identification. The M45 can be obtained in a practice type. It has a black powder charge in place of a tetryl booster charge, and is designated as a point practice fuse. The head is painted blue, and Fuse, Point, M45, Practice" is stamped on the body.