|Thickness on top||125 mm|
|Outer diameter||540 mm|
|Inner diameter||300 mm|
|Height (+ ceiling part)||1646 mm (+ 300 mm)|
The 420P9 was designed for the Festungs Flammenwerfer also known as Festungsnahkampf Gerät. An armoured tube was also made for the F.N. Gerät in Baustarke A, the 457P01. However, it doesn't look like this part was ever used somewhere.
Probably because of the enormous fuel usage and the complexity of the weapon, the F.N. Gerät was not much used. They were part of the standard armament of the Oder-Warthe-Bogen Panzerwerke and Westwall B-Werke. Only two examples can be found in the Atlantikwall, built into a tunnel system at Ba 39 and 40 in Biarritz.
Below is a detailed description of the F.N. Gerät of Werkgruppe Seeckt (B-Werk No. 1520) near Irrel, also known as Katzenkopf, made by American Ordnance Technical Intelligence Team No. 3 (Capt. W.J. Lord, Sgt. John Jakovljevic and T/5 Otto Haas) and published on 3 June 1945. Except for several small changes this is the actual text from 1945.
a. This unit, the “F.N. Gerät”, is a disappearing type flame thrower unit designed for the neutralization of any assaulting enemy who might advance to the immediate neighborhood of the fort or who might be on top of the fort.
b. The range of this flame thrower, according to the instruction manual, is fifty-three yards (48 meters); traverse is 360°. The fuel is flame oil, ignited by acetylene, the oil being projected thru a one-half inch (13mm) diameter nozzle at the top of a circular steel shaft. The head of this shaft, normally covered by a mushroom shaped, armor steel, hood weighing about one hundred and fifty pounds (68 kg), is below the roof of the fort except when in the firing position when it is 16 inches above the earth on top of the fort roof.
c. The complete installation requires three levels: the roof, the control room (No. 27), and the fuel and pump room (directly below the control room). The main parts of the equipment are: the shaft or pipe, the mechanism for elevating and rotating the shaft, and the mechanism for throwing the flame.
d. The shaft (l) which projects from the control room, is seven and one-half inches (190 mm) in diameter. Inside, it carries the pipes for the flame oil and the acetylene, the ignition cable, and one reserve pipe. (Prisoner stated that this reserve pipe was for poison gas. No poison gas was found in this fort). The base of this shaft contains connections for the ignition cable and for hoses carrying flame oil and acetylene. The shaft is guided in an armored ring (2) which is set in the concrete of the roof, and in a flange (13). The upper part of the shaft is constructed of armor steel as is the hood (3). The head of the shaft contains the nozzle (4), three gasburners, and two sparkplugs.
e. The lower room contains the motor (3) operating the hoist mechanism for elevating and lowering the shaft and rotating it in traversel; in the upper room, No. 27, is a unit (15) for manual operation. In the corner of this upper room is the electrical control unit for operation of the flame thrower.
f. In the lower room, in addition to the hoist motor, are the 2500 liter (660 U.S. gallons) flame oil storage tank (23), rotary oil pump (27), pressure tank (16), nitrogen bottles (24), and acetylene bottle (25).
h. It appears, from the examination of the turrets and earth in the roof, that the flame thrower of this fort had not been used to defend it. No doubt the accuracy of the tank destroyer crews during firing on the machine gun turrets convinced the personnel in Panzerwerk Seeckt No. 1520 that surrendering was the better part of valor. The accuracy of the 76th Division, XII Corps, riflemen, whose small arms' fire against the mirrors of the disappearing telescopes of the mortar, artillery observer and machine gun turrets was so effective, no doubt increased the desire of the fort personnel to see again the open sky over their beloved Deutschland, past the border of which they were soon to journey to the protective enclosure of a prison stockade.