Ed Tinker was kind enough to provide me with one of his original 8mm Nambu cartridges [
Thank You, Ed!].

I've attached a pic of it (on the right) compared to a 7.63mm x 25 cartridge headstamped '541 44' (Presumably a C96/M30 Mauser cartridge).
I found it interesting that the Nambu has the same three indentations spaced evenly around the neck to further help hold the bullet in place in the case. Was this typical of all WW II cartridges, or just the Axis powers???
There is also no headstamp on the Nambu round. Was there only one facility providing ammunition for the 8mm nambu, or is this an example of wartime expediency???
Extractor groove is much thinner than I expected...Also interesting is that the rim is within .001" dia of the base...COTW states that it should be 'semi-rimmed', but they only list a .005" dia difference...
(BTW: I've found COTW to be quite lacking in detail)
Edit: I've bought Ed's last OEM 7mm Nambu cartridge...You would not
believe how much these old cartridges are going for!!!...