30X173 BRASS Shell Case

  • I have a fired 30X173 rimless shell case made of BRASS with these impressed headstamp markings: “Oe”, “A”, “51” and “D4”. The shell case has a short neck [15.5mm in length] with an electric primer screw [the type with 3-wrench holes] with the diameter of 14mm. My 30X173 brass shell case is exactly 173.3mm tall. I assume the mark “Oe” is the logo for “Oerlikon” and “51” is the two digit date for the year of shell case manufacture [1951]. I know that the 30X173 KCA shell cases are made of steel and those made of aluminum alloy are manufactured in USA. My questions are: — 1] Was my 30X173 brass case made in Switzerland??? If not, which country made it??? — 2] Could the headstamp letter “A” be for the “Altdorf” ammo plant [Canton of Uri / Switzerland]??? — 3] Which weapon fired my 30X173 rimless brass case??? Thanks in advance for any help, Liviu 12/26/06

  • I’m surprised nobody has an answer for me. I was able to find a similar fired 30X173 rimless BRASS case which is headstamped: “Oe”, “A”, “52” and “D5”. It has the same type of [fired] electric primer screw. The headstamp markings from the first 30X173 brass case [see above] are: “Oe”, “A”, “51” and “D4”. Making a comparison it’s clear now that “51” and “52” show the year of the shell case manufacture “1951”/“1952” and the letter “A” is the shell case maker’s mark [“Altdorf”?]. What exactly the marks “D4” and “D5” do they mean??? Shell case lot number??? Liviu 12/30/06


Perhaps we can get an answer with another try?


Oerlikon did a huge amount of research and development in the 1950s, producing many experimental guns and cartridges, especially revolver cannon. The Oerlikon KCA aircraft gun was the first of their revolvers to be adopted, but its ancestors went back through a few “generations” of development.

I am not at all surprised that the prototypes of what eventually became the steel-cased electric-primed 30x173 KCA round were made in brass - the same applied to the contemporary HS 30x170 (which of course reverted to brass when adapted for use in the Rarden gun). I suspect that it was simply easier to make brass cases, requiring less expensive machinery, so they did the development work in brass before switching to production in steel.

The 30x173 as adapted for the GAU-8/A was of course modified to use a light-alloy case, percussion priming and plastic driving bands. It has now been modified again - back to steel, but retaining percussion priming - for use in the Mauser MK 30/2 (the MK 30/1 still uses the light-alloy ammo). I understand that the Bushmaster II/Mk 44 can use either.

  • I hope so. Liviu 07/05/07