158 mm shrapnel-type jet mine

  1. a spiral ballistics hood;
  2. a reactive powder charge chamber;
  3. ribbons;
  4. pressed charge;
  5. turbine;
  6. aluminium foil;
  7. bursting charge case;
  8. bursting charge;
  9. detonator;
  10. bottom detonator;
  11. throwing charge;
  12. weight class;
  13. BB designation.

The rocket-propelled grenade was intended to fire the German six-barrel 'd' mortar (see description).  The stability of the jet mine in flight was ensured by a special turbine (see figure) with a screwed or welded case, which contained a bursting (and in the case of special mines - chemical or smoke) charge, detonator and bottom fuse. The turbine had 26 nozzle holes with a diameter of 5.5 mm around the circumference, drilled with an inclination of 14°. When the shot was fired, the reactive powder charge was ignited by an electric ignition inserted into one of the turbine nozzle holes. Gunpowder charge gases flowing through the nozzle holes caused the mine to receive not only progressive but also rotational movement.

As a reactive powder charge, a pressed smoke gun or a pressed nine-channel diglycol powder gun was used.

The charge in the form of a pressed checker made of smoke powder consisted of a case, a powder checker and felt tapes. The charge in the form of a pressed 9-channel diglycol gunpowder checker (see figure) consisted of a case, a gunpowder checker, a bottom nozzle, a ring, a ring gasket, a gunpowder ignition and eight celluloid tubes.

The electric igniter, designed to ignite a mine, had a contact cone and a contact plate on its front side. When short-circuited from the igniter, current flows to the junction box, then to the spring contact, which is inserted into the ignition contact plate with its tip. The return path of current goes through the contact cone of the fuse on a mine, a mortar to the electric ignition machine.

The table weight of the mine is summed up from the average weight of the individual parts, expressed in kg:

Name of individual parts  Shrapnel blast mine
Smoke gunpowder charge  Diglicole charge. Gunpowder.   
1 Enclosure with screwed-in turbine and bursting charge  15,25  15,25
2 Powder charge 21,65  18,10
3 Bottom fuse  0,10  0,10 
4 Detonator 0,06  0,06 
5 Ballistics hood 2,00  2,00
  Tabular Weight 39,06  35,51

By weight, mines were divided into three classes: underweight (with sign I), normal weight (with sign II) and overweight (with sign III). The sign was painted on the projectile body near the turbocharger.

Type of gunpowder charge Weight class in kg  The average weight of a projectile mine
fuse and detonator free
Tabular Weight
Smoke gunpowder head up to 38,70 38,70-39,10 over 39,10 38,90  39,06
Diglycol powder head  up to 35,15  35,15-35,55 over 35,55  35,35  35,51 

The assembly of jet mines.

Jet mines were assembled in special workshops in compliance with the safety regulations established when working with ammunition and explosives. Compliance with all safety measures was particularly necessary due to the use of pressed smoke powder draughts as throwing rockets, along with diglycol powder.

The assembly of the mines was carried out in a special machine and consisted of the following operations:

  1. Screwing the turbine with housing to a reactive powder-charging chamber. In this case aluminum foil with diameter 140 mm and thickness 0,05 mm was placed in the place of connection of the turbine with the reactive powder-chamber. When assembling the mine it was necessary to ensure that the reactive powder-chamber and the turbine with the body were of the same weight class.
  2. Screwing on the ballistic hood.
  3. Calibrating the collected mine using the calibre or the mortar barrel.
  4. Inserts of explosive charge, central tube and detonator. The bursting charge and detonator were fixed in the central tube on the sides with strips of paper, and in height with cardboard mugs.
  5. Screw-in bottom detonator. The detonator was not supposed to protrude from the bottom of the mine body.

External inspection and assembly of the charge from the smoke powder.

For external inspection with a wooden knife, a waterproof shell was removed from the surface of the gunpowder. The surface of the gunpowder checker should not have cracks, mechanical inclusions and destruction caused by humidity. The latter could appear in the form of surface spots, raids from separated nitrate or sulfur. The felt pads on the ends of the gunpowder checker should have been well glued.

After external inspection, an adjusting ring was placed on the upper edge of the charge case and 6 felt bands (see the figure) were evenly hung on the inner surface of the case, which were fixed with their ends through the holes in them to the ring clamps. The belts were to be 30-40 mm from the bottom of the case, and the holes in the belts were to be 20 mm below the top edge of the case. The felt pads glued to the ends of the gunpowder checker should protrude no more than 2-3 mm beyond the edge of the case.

The charge from a smoke-powder checker was inserted into the slipcase when lightly pressed. In case of sticking of a powder draughts while pushing it into a case it was necessary to change felt tapes for thinner ones. Conversely, if the belts were thin and therefore did not secure the gunpowder charge (draughts), they should be replaced with thicker belts.

External inspection and charge assembly from diglycol powder.

During the external inspection of the charge, those gunpowder checkers, which had hollows, uneven ducts, air and mechanical inclusions, as well as checkers with a large surface roughness, were to be discarded.

A checker made of diglycol powder, which had undergone an external examination, was freely inserted into the case, on the bottom of which a soft bottom gasket was placed and fixed with 8 celluloid tubes retractable into its marginal recesses. Then a ring nozzle with a powder cap and a ring ignition charge was applied to the powder cap.   The finally equipped mine was placed in its carrying case. The weight of the empty carrying case was 3.25 kg. The case with the fragmentation and blast mine weighed about 42kg with a smoke powder charge and about 39kg with a diglycol powder charge.

Discharging the mine and packing its elements.

Jet mines were discharged in the following sequence:

  1. The bottom fuse was unscrewing.
  2. The detonator was coming out.
  3. A burst charge was removed in special mines and then the central tube was unscrewed.
  4. The mine body with the turbine was unscrewed and removed.
  5. Powder charge was removed from the charging chamber. If the gunpowder was not removed from the chamber even if the edge of the chamber was lightly tapped on wood, the charge was left in the chamber on which the safety hood was put.

After discharge, individual elements of the jets were externally inspected, cleaned and packed in a special capping. Bottom detonators, detonators, explosive and combat charges were packaged in an airtight cavity.