Thanks for the responses guys, I must admit im playing catch up with this one, I had no idea they modified the service cartridge too.

I would hazard a guess the fractional reduction in case length was to aid possible extraction related issue.

I can't see what difference 1mm would really make, but perhaps just enough.

The suggestion of violent recoil in my book, would certainly suggest a good deal of refinement was still required and must have been a handful to deal with, considering the relatively small build of the average Japaneseicon soldier.

Anyone know how many were made?