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Japanese 13mm WWII Taperbore Tests

E

EODGUY

Well-Known Member
The Japanese did experimental work with developing a Gerlich type taperbore round for a 13mm machinegun during WWII. They developed a muzzle velocity of 1300 m/s but the resulting bore pressure was too high. To reduce pressure they mixed small grain propellant with larger chopped cord propellant, which was partially successful. A typical projectile had two copper skirts on a steel body. One design used a one-piece copper projectile (possibly gilding metal, but there was no mention of that). Tests showed this design did not fit tightly in the barrel when fired. At least three different barel designs were also tried. Design and testing was far from complete when the war ended, which stopped all further development.
Sorry for the quality of the drawing, but my original is not much better.
 

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Japanese Gerlich

Very interesting information. What is the reference for the drawing? US Intelligence reports?

Regards
TonyE
 
I guess these are the bullets that where used in tests by the jpn. navy.
They used different barrels and a 25mm case for the propellant.
The projos where loaded into the barrel and then the 25mm case behind in the chamber.

Report could be downloaded here

http://depositfiles.com/files/67c3akhyj



.
 
Last edited:
The information came from "O-39-2" a US Navy Technical Misison to Japan report dated 18 February 1946. You are correct about the 25mm case. The three experimental guns were chambered to acccept the HO Type 25mm case necked down to 13mm. Gun #1 fired 86 rounds, gun #2
fired 102 and gun #3 fired 118 rounds.
 
EODGUY said:
The three experimental guns were chambered to acccept the HO Type 25mm case necked down to 13mm.
Click to expand...
Interesting, thanks for posting the info Bob.
I wonder if any of the cases survived.
Do you have any drawings/photos of the cases?
Dave.
 
Hi,

Ken Elks has them featured on pages 84 and 85 of his excellent work on Japanese ammunition (part 1).

As this is copyrighted material, I cannot blatantly post a scan of it here. Let me know if you have trouble tracking down a copy of it, and then perhaps I could transcribe what he wrote about them.

Cheers,
Olafo
 
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