20x138B cartridges, Germany WW2
Cutaway models of the 20x138B(Belted) cartridges in my collection. Amongst collectors the 20x138B cartridge is quite popular as these have been made in large quantities by many countries in numerous types, both WW2 and post WW2. However, it can safely be stated that Germany developed the most numerous types –as well service cartridges, as well as experimental- of all countries that used the 20x138B cartridge.
Originally , the Solothurm factory was a clock factory. It later became involved in weapon production. In 1929, most shares of the Solothurm AG arms factory were sold to Germany.
Around that time, the need far a one man served heavy anti tank rifle arose. Under German engineering supervision two nearly identical weapons were designed; the S-18-100 and the S-18-1000. These were heavy anti tank guns with a tremendous recoil, used from a three point support, and designed in such a way that the cartridge was allready fired when the locked combination of barrel and breechblock was still moving forward (is called soft recoil today).
The S-18-100 gun uses the 20x105B Solothurm cartridge. Orders for these guns and cartridges were placed by Germany, Hungary and the Netherlands -who wanted to use the 20x105B as an aircraft cannon-.
The S-18-1000 gun uses the 20x138B cartridge, which was preferred by many countries over the 20x105B cartridge as the 20x138B cartridge was much more powerfull. Germany used it in it’s famous 2 cm Flak 28/30 and the feared 2cm Flak 38 quadripple gun, Italy used it in the 20x138 Breda gun, the Netherlands used the 20x138B cartridges in it’s S-18-1000 Anti tank rifles. Other countries to use the 20x138B cartridges for their anti aircraft guns were: Austria, Finland, Sweden and Switzerland. German design of cartridges for the flak guns was mainly done by Rheinmetall.
Post war versions can be found, although most often these are used as subcalibre training devices for tank guns. Most often these are of Yugoslav or Czech design.
The shellcases can be found in Brass and steel. Before 1939, only Brass cases were used. In WW2, due to lack of strategic resources as copper, the germans started using steel shellcases. These were either copper plated, either baked on laquered finished in brown or green. Last days of the war productions shellcases are laquered only.
The powdercharge with German shells is placed in a two piece powderbag, the upper one containing the main charge, the (small) lower one houses the booster charge. The type of fabric used for these powderbags may vary.
When the projectile has an impact only nose fuze, it has a tracer self destruct element, either pressed in, either screwed in. Normally used impact fuzes are the AZ-1502 F, the AZ-5045- The AZ-45, The AZ-46, the AZ-47, the AZ48, the AZ-49 and the AZ-53. Functioning of these fuzes is quite alike in most cases; a firing pin with a flange in top is kept in upper position by either two centrifugal weights with a wound spring around it below the flange, either a rolled up foil coil below the flange. Upon firing the weights are thrown outward, releasing the firing pin, either the foil coil unrolls, releasing the firing pin.The firing pin is floating now. Upon hitting an object, the hammer pin above the firing pin wil hit the firing pin down into the duplex detonator, exploding the projectile.
If the projectile has no Tracer self destruct (cartridges 08/09/10) the “2cm Kpf.Z.Zerl. Fg” mechanical self destruct fuze is used. This type of self destruct mechanism was used for the first time in this particular type of fuze, and is still in widespread use with smaller calibre mechanical self destruct fuzes today.
Functioning of the mechanical self destruct mechanism disc:
The disc is placed below a spring tensioned ring that exactly fits the hole in the centre of the disc. The ring wants to push the firing pin down by it’s disc into the detonator, however the ring is held in upward position by the release (R), which prevents it from moving down. The release has a hook on one end (green arrow) which rotates around a pivot pin (P2). It is held in position by a banana shaped hook which pivots around a pin (P1). It hooks in the release (green arrow). The banana shaped hook is held in position by a leaf spring (blue arrow). On firing, the weight (W) is thrown outward, enabeling the leaf spring to move outward. As long as the centrifugal force is large enough and the weight (W) is thrown outward, the two parts hook into each other (green arrow). As soon as the centrifugal force decreases, the rotation spring surrounding the pivot (P1) starts to push the weight (W) inward, releasing the hooks (green arrow). The release (R) can now move outward, enabeling the ring to pass through the centre hole and push the firing pin down into self destruct.
Base fuzes with a safety mechanism (18 ) for APHE-T (Armour Piercing High Explosive) projecttiles are not often found in German use. Normally one used screwed in base plugs with a build in self destruct mechanism (16). Upon hitting a target, the generated heat will explode the APHE-T projectile, when the target is missed, the heat of the tracer will ignite the self destruct mechanism at the end of the tracer.
Cartridges were fed with a 20 round box magazine.
The firing rate of the gun is 120-180 Rpm
Vo: around 900 mtrs/sec (2,.953 ft/sec) (depending upon type of projectile)
Effective range: 2.200 mtrs. (2.406 yards)
The last time the gun was “officially” used was in the Yugoslav wars at the end of the last century where often the quadriple version could be observed, being used by all fractions.
Type of cartridge and description:
01- 20x138B, inert, tar filled M-shell body, used for Czech post WW2 subcalibere training device for tank gun. (is used in same training device as cartridge 20).
02- 20x138B, inert, red phosporus filled, live detonator, used for Yugoslav post WW2 subcalibere training device for tank gun. Brass shellcase. Yuguslav manufactured with sometimes original German projectile bodies. Vo: 920 mtrs/sec.
03- 20x138B, inert, red phosporus filled, live detonator, used for Yugoslav post WW2 subcalibere training device for tank gun. Steel shellcase. Yuguslav manufactured with sometimes original German projectile bodies. Vo: 920 mtrs/sec.
04- 20x138B HE-T-SD. Has a large, screwed in tracer ending in a brass self destruct element placed in the main charge. Brass fuze with wooden hammer pin in nose. Italy, WW2
05- 20x138B HE-T-SD. Has a screwed in tracer ending in a self destruct element placed in the main charge. An aluminium impact fuze is placed on the projectile. Germany, WW2
06- 20x138B HE-T-SD. Has a small pressed in tracer in top of the drilled tracer hole ending in a self destruct element placed in the main charge. An aluminium impact fuze is placed on the projectile. Germany, WW2. Most commonly found. Germany, WW2.
07- 20x138B Incendiary (Br) shell. Filled with an incendiary explosive charge. Germany, WW2.
08- 20x138B HEI-SD shell. High explosive with a mechanical self destruct fuze. Germany, WW2.
09- 20x138B HEI-T-mech.SD shell. High explosive with a mechanical self destruct fuze. Has a loose incendiary element in the lower portion of the projectile body. Germany, WW2.
10- 20x138B HEI-T-mech.SD shell. High explosive with a mechanical self destruct fuze. Germany, WW2.
11- 20x138B practice tracer, inert (tar) filled, Germany, WW2.
12- 20x138B practice tracer, Germany, WW2.
13- 20x138B blank shot with wooden projectile and reduced charge under felt wad. Germany, WW2.
14- 20x138B rubber clad drill cartridge with steel shellcase base, Germany, WW2.
15- 20x138B API-T. Armour piercing Incendiart –Tracer. Contains an aluminium cylinder with 3 grams of white phospor. Germany, WW2.
16- 20x138B APHE-T-SD. Armour piercing explosive with screwed in tracer self destruct element. After tracer has burnt up, the SD element is activated, exploding the projectile. Germany, WW2.
17- 20x138B APHE-T-SD. Armour piercing explosive with pressed in and swaged tracer self destruct element. End of war production. Very dangerous type as it can easily be misidentified as a AP-T. Germany, WW2.
18- 20x128B APHE-T-SD. Armour piercing High explosive with tracer sels destruct. Two pins keep the firing cap in a fixed (backward) position. The pins are held inward by a foil coil. After firing the pins are thrown outward, releasing the firing cap. Upon impact, the firing cap is thrown forward in the firing pin. If no target is hit, the end of the tracer ignites a black powder pill that propells the firing cap forward in the firing pin.
19- 20x138B for the Dutch bought Solothurm S-18-1000 anti tank Gun. Cartridge of AP-T design. Colour is brown with a white band over the driving belt.
20- 20x138B AP-T as used in a Czech subcalibre training device in the T54 and T55, post war. (is used in same training devive as cartridge 01).
21- 20x138B pzgr.40 (HVAP). High velocity armour piercing with Tungsten core. Aluminium projectile body. Germany, WW2.
22- 20x138B practice pzgr.40 (HVAP), steel body with screwed in baseplug. Germany, WW2.
If anybody has any more types of this 20x138B cartridge , please do not hesitate and post a picture!
Last edited by PzGr40; 19.12.2013 at 13:01.
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