20mm x 138B

Please, help me to identify this 20mm x 138B

The headstamp :
0 o’clock : 20mmM53
3 o’clock : BK (in a circle)
6 o’clock : C45602
9 o’clock : TK (in a square)




A TP-T to be correct.

  • The 20mm projectile muzzle velocity is clearly marked: 920 meters per second. I may be able to find more. Liviu 11/10/07

It is very cool! Looks to be in really nice shape.

  • @ Michael: With great help from Mr. B. Bogdanovic I can say this about your Yugoslav made 20X138B belted round: It is for insert barrel [for Conversion Device] tracer shell. Like I mentioned already above the 20mm projectile muzzle velocity is 920 m/sec ( Vo = 920 m/sec ). The mark “RZK8901” stands for "Overhauling Institute Kragujevac from the year 1989, month of January [01]. The headstamp markings: “20mm M53” [type, model of round]; “TK” in a square [technical control stamp]; “VK” in a circle [“BK” marked - military control stamp]; “C45602” [serial number]. I hope this helps you. Liviu 11/11/07

Great info, thanks Liviu

  • @ Michael: Avec plaisir! Actually the person who deserves to be congratulated is Mr. B. Bogdanovic. If I’m not wrong, after 1945 the 20X138B rounds were used by Czechoslovakia and Yugoslavia. Any other countries which used the 20X138B round after 1945??? Liviu 11/11/07

Norway + those who used up German ammo and did not produce new one. Not to forget the US-production pre 1945.

The French Army did use the Fla 38 gun until the end of 50ies. Most of the guns were, as a matter of fact, in the F.F.A. units, i.e. Forces Fran

  • Very interesting, thank you both. Liviu 11/11/07

I have a vague recollection that Finland used the Vierling (four-barrel) AA mounting in this calibre for quite a while after WW2.

You will find all the details about 2cm German Flak 30, Flak 38 and 2 cm Flakvierling in Finland in the excellent book (in Finnish language, but with english captions too) “20 mm Suomessa”, by Mika Pitk