On February 10, 2025, X user “JGSDF 2AAGP 305ACO” posted a partial photo of what appears to be a Nambu Model 2 Ko 6.5mm submachine gun.
The weapon has a bipod, the barrel casing has no cutout, and there is no protrusion for attaching a bayonet.
Remarkably, traces of the bipods also remained on the Nambu Model 2 Otsu 8mm submachine guns.
This also confirms Killerwolf1024’s theory.
Apparently, a large number of receivers were made for the 6.5mm model. In the case of prototypes, it was probably easier to slightly modify the existing parts for the 8mm model.
Based on an excerpt from this photograph, a drawing of the Nambu Model 2 Ko submachine gun was made.
Although since the bayonet is still missing (which is sad 
), I changed the drawing a little.
I would also like to note the topic from the user NonNational.
Of course, the value of the document he provided and its translation is very great for us, however, I am confused by the time frame in which the document was drawn up.
On the JACAR website itself, the document’s creation date is listed as the period from January 9, 1926 to January 21, 1926.
The title page of the document also speaks about this.
Of course, in 1926 there was no talk of creating the Nambu Model 2 submachine gun. By that time, even the Tokyo Arsenal submachine gun of 1927 was not yet ready. The highly respected researcher of Japanese weapons, Jiro Sayama, writes in his book “小銃拳銃機関銃入門” that preliminary research into the Nambu Model 2 submachine gun began only in 1935!
This suggests that there were at least two weapons chambered for the Type 95 experimental cartridge, created in the mid-1920s and mid-1930s.
I also contacted JGSDF 2AAGP 305ACO, asking for a full photo. He replied that such a photo does exist and he plans to publish it someday.
With this thread I wanted to update the information about the Nambu Model 2 Ko in 6.5mm, since I often see people refer to Killerwolf1024 or NonNational 
.