The Nahverteidigungswaffe - Characteristics

Design

The Nahverteidigungswaffe consisted of a circular plate and a launch tube that was bolted to the roof of the tank and covered with an armored plate. The launch tube had a hinged breech. The breech was opened and closed by the use of a locking handle. The handle was rotated 90 degrees clockwise to unlock the breech and allow it to be flipped upwards. After loading the breech was closed and locked by rotating the handle back 90 degrees counterclockwise. The base plate mounting had a locking screw to allow the operator to lock the NahVtdgW in a particular direction. The launch tube was set at a fixed 39 degrees from the vertical. The diameter of the launch tube was 92mm.

These two images show the Nahverteidigungswaffe in the open position. The one on the right shows the Verschlußstopfen in place

Ammunition

The Nahverteidigungswaffe could use a variety of ammunition types. 

Schnellnebelkerze 39, smoke candles. This was the primary ammunition type and the one that determined the diameter of the launch tube (92mm).

A Sprenggranatpatrone of indeterminate type and nomenclature. The Tiger B manual calls for this round to be Sprenggranatpatrone 326 Lp. As will be shown below there are still some questions to be answered concerning this round. Whatever the name it was a high explosive round that had a range of 7-10 meters and with the timed fuze of 1 second would normally explode 0.5 to 2 meters above the ground. This round was fired from a normal Leuchtpistole (flare gun) or Kampfpistole (rifled flare gun) using the Nahverteidigungswaffe tube as a large pistol port. The caliber was "4-bore" and nominally 26.65mm but actually nearer to 26.9mm. Sources conflict on the size of the explosive charge. It was used to combat close assaulting infantry in the "dead zone" around the tank.

Rauchsichtzeichen orange 160, colored smoke cartridges

Leuchtpatronen, standard signalling munitions including starclusters and illumination rounds

Sprenggranate

The picture above and the drawing that follows below are of the original Sprengranatpatrone 326 Lp designed to be fired at ranges up to 400m. The impact fuze in the nose cone clearly indicates this. The round used to defend the vehicle had a timed fuze and wouldn't need an impact fuze. The round we're interested in had a thicker case and a bigger charge but it was still small. It was much smaller than the 5cm rounds used with the 5cm Light Mortar, le.Gr.W.36. This mortar was withdrawn from service because it was found to be ineffective. This calls into question the efficacy of the Nahverteidigungswaffe in defending vehicles from close assault. The HE charge was small and probably had less of an effect than a regular hand grenade fitted with a fragmentation sleeve. Research continues on the exact size and power of this grenade.

UPDATE:

It still has been impossible to locate any evidence of a special Sprenggranatpatrone 326Lp with a timed fuze as called for in the Tiger B manual. However,numerous references and photos of a special time-fuzed round designed for the Kampfpistole (also known as the "gezogene Leuchtpistole" - "rifled signal pistol") have been found. Not much is known about this particular round. It was shrouded in great secrecy and documentation about its charcteristics is very rare.

Some numbers on the Sprgrpatr. 326 Lp itself have also been found. Development was started in 1937 and although the army later lost interest in it, the Waffen-SS was very interested in persuing its development. Though this round was advanced and well made, its performance was not as good as other rounds of the same caliber. It was later replaced by a much simpler construction that had a bigger HE charge. This new round was called a 2.6cm Wurfgranate and sometimes mistakenly referred to as a "Sprengranatpatrone 326 Lp neuer Art", though its design had nothing in common with the original. Though this round had slightly better performance it effectiveness was still markedly inferior to that of the standard rifle grenade. Tests used by the Germans to measure this performance showed less effective fragmentation than the other comparable rounds like the impact-fuzed Sprengranate für Leuchtpistole Z (Kampfpistole).

In addition the Rauchsichtzeichenpatrone was also known as the Deutpatrone Z and like other cartridges with the Z was designed to be fired from the Kampfpistole and could not be used with the normal Leuchtpistole. There was not, as far as can be deteremined, a comparable round for the normal Leuchtpistole. This would indicate that propably the Kampfpistole was the actual device used in conjunction with the Nahverteidigungswaffe.

Nebelkerzen

It is apparent that the primary function of the Nahverteidigungswaffe was to place smoke candles. The size of the tube was determined by the size of the Nebelkerzen. The original Nebelwurfgeräte mounted on many vehicles were removed after incidents of small arms fire igniting the candles in the dischargers and the resulting smoke incapacitating crew members. The Nahverteidigungswaffe allowed the smoke candles to be discharged from under armor. The Nebelkerzen were the only munition that the Nahverteidigungswaffe actually "fired." The rest were fired using the Leuchtpistole/Kampfpistole.

The Zündladung N4 is the blasting cap used to activate the smoke candle after discharge.  It was inserted into the bottom of the smoke candle  and then the Wurfladung was screwed into the cover the Zündladung.  The round was then inserted into the launch tube.

After the breech was closed the Zündschraube C43 St was inserted into the breech cavity and used to  fire the Wurfladung and thus the smoke candle.

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