Original Item: Only One Available. The 81 mm Mortar High Explosive (HE) round is a fin-stabilized, naturally fragmenting round intended to be fired from muzzle loading smooth bore mortars. The round is provided with point-detonating fuze and it is delivered as a ready to fire in resealable multi-round containers, equipped with a fuze and charge system.

Totally inert and demilitarized according to BATF guidelines with hollow body and solid deactivated fuse. This mortar round cannot be converted to an explosive device and is not available for export.

This is a totally genuine United States military Vietnam or post war produced SHELL, M43, possibly produced as an inert practice round. It has a complete and inert M734 multi-option fuze with bakelite nose cap. The housing can be removed to inspect the interior of the round, which is entirely hollow. The bottom fins can be removed as well.

The heavy OD green repaint has obscured any markings that would have been found on this round, so we estimate that it was produced either during or after the Vietnam War.

Perfect for any display!

M734 Fuze
The M734 multi-option fuze is a rangefinder and collision detection system used on 60mm, 81mm, and 120mm mortar shells as a trigger to detonate the shells at the most damaging heights of burst when combating four types of battlefield threats:

-The rangefinder is a Doppler radar using FMCW technology to emit a radar signal and can be set to trigger two types of air-bursts, one being a near surface burst to combat standing targets and the other being a higher proximity burst downward onto prone or dug-in targets.

-The collision detection portion of the fuze consists of two mechanical devices, one being a quick response electric inertial switch for a burst upon impact with a target, such as a vehicle, and the other being a slow response mechanical detonator that allows shell penetration, such as through a forest canopy, before detonating.

This integration of four functions into a single fuze reduces the logistics and cost to support mortar crews on the battlefield.

Settings
A typical mortar firing procedure is for a squad leader to select a target and call for one of the four fuze settings. A gunner sights the mortar onto the target and an ammunition bearer sets the fuze. An assistant gunner drops the shell into the tube upon a command to fire from the squad leader.

Tools are not required to install or set the fuse. It is adjusted by hand, even with Arctic mittens, simply by rotating the top of the fuse clockwise until a three-letter engraving is above an index line. Additionally, the setting can be changed any number of times without causing damage to the fuze. The four engravings around the circumference of metal housing of the fuze have the following meanings for detonation height:

PRX = Proximity air burst between 3 and 13 feet
NSB = Near surface burst between 0 and 3 feet
IMP = Impact burst on contact. (In the event an IMP setting fails, detonation is 1/2 second after impact.)
DLY = Delay after impact of 0.05 seconds in the fuze explosive train before the shell detonates.

In all four settings, the high explosive in the mortar shell is detonated by a cascading explosive train of four increasing energies within the fuze. These are the Microdet electric detonator, the explosive lead, the explosive booster, and the delay primer assembly functioning as follows:

- In the PROX, NSB, and IMP fuze settings, a firing circuit applies a voltage to the small Microdet which faces and ignites a bigger explosive lead that channels into the explosive booster which initiates the shell's high explosive.

- In the DLY setting, the explosive lead is initiated instead by the delay primer assembly, which operates even in the event of power supply or electronics failures.

- Reliability against duds is increased by the fact that if the M734 fails to detonate the mortar shell at one setting, it will immediately and automatically use the next one along, i.e. failure at the PRX setting causes NSB detonation to be selected. Similarly, failure to detonate at the NSB setting will automatically cause IMP to be selected, and so on.

- This redundancy is a safety factor designed to prevent malfunctioning mortar shells from being buried upon ground impact and becoming a risk to civilians after a battle or becoming ammunition for enemy activities.

The M734 fuze was developed at the Harry Diamond Laboratories (HDL) for the 60mm lightweight company mortar system, which now is managed by the Armament Research Development and Engineering Center (ARDEC) Fuze Division. It was determined to be suitable for army use in July 1977 and accorded type classification standard. To demonstrate readiness for transition into full rate production by the Armament Munitions and Chemical Command (AMCCOM), ARDEC/HDL managed the first production for war reserves as well as the construction of automated initial production facilities (IPF) for mobilization readiness. HDL awarded three competitive contracts in 1978/79: Eastman Kodak (Rochester, NY) for the fuze assembly and IPF, Motorola (Scottsdale, AZ) for the amplifier assembly and IPF, and Alinabal (Milford, CT.) for the alternator assembly and IPF. After successful first article inspection and production lot acceptance tests, transition was completed in March 1983. AMCCOM performed all procurements for stockpile with technical support by ARDEC. The Army Mortar Plan issued in 1985 expanded use of the M734 fuze to 60mm, 81mm, and 120mm mortars. Improvements in the fuze reliability and performance by ARDEC engineers led to production of the M734A1 fuze manufactured by L-3 FOS (Formerly KDI).