9mm Japanese rimmed ammo

Can anyone that has an original round please measure it and give me an overall length of the cartridge please?


1.190 in.

Think you will find two different OAL one BP & one smokeless (shorter)

I have 2 listed in books.

1.18" OAL
30.5MM (1.20")

and now 1 in the middle at 1.19"

Could the 1.18" be the BP round and the 1.19-1.20" be the smokeless loading?

Elks’ description of the smokeless loading mentions an overall lenght of 1.14" (29 mm).

I wouldn’t place absolute faith in the belief the smokeless and black powder charged 9 m/m Japanese revolver cartridges can be distinguished on the basis of their overall length. I checked my four specimens, plus one fired case with expended primer. All four of the loaded rounds were close enough to 30 m/m (1.18 in.) OA to round off at that height. These cartridges weighed 200.5, 203, 204, and 204 grains each. The fired case weighed 51.5 grains and had been charged with smokeless powder when fired.

Add 149 grains for a bullet (per White and Munhall) to that fired case, plus 3 grains or so for a smokeless propellant charge and you just about have 204 grains. The cartridges mentioned above are from various sources, but the fired case and one of the 204 grain specimens are from a common source. I would guess a black powder charge for this cartridge would be on the order of 12-14 grains. Jack

The two I have:

One weighs 202.6 gr & oal is 1.182" / 30.03mm.

One weighs 213.6 gr & oal is 1.198" / 30.44mm.

Pete: That’s interesting. I’d wonder if the heavier one might not really be a black powder load. Thanks. Jack

[quote=“PetedeCoux”]The two I have:

One weighs 202.6 gr & oal is 1.182" / 30.03mm.

One weighs 213.6 gr & oal is 1.198" / 30.44mm.[/quote]

OK… been checking some things out… Pete, would you be able to check the diameter of the 2 bullets and see if they are different??

My type 26 revolver seems to have a barrel diameter of .361" on the grooves…

I have been doing some reloading and found that the .356" bullets I am using are keyholing at 30 feet. The .358" bullets are doing much better.

MissingSomething–Please keep in mind that no reloading discussion is allowed on this Forum. So far everything you have said is acceptable, but please do not go into powder charges for reloading, etc. Discussion of original factory powder and primer information is allowed.

It appears that there is a little discrepancy between books that have this dimensional information in it.
Can I get someone to measure the bullet diameter please.

Can I get someone to measure the original bullet diameter please.

Missing: An accurate measurement of an original bullet will likely require disassembly of a cartridge. I can tell you that White and Munhall give a max. diameter of .355 in. Harry Derby’s Japanese pistol book (first edition) quotes a Japanese source as 9m/m (.354 in.). Jack

Thanks Jack.

As mentioned there is some discrepancy with the books. I would like to see if someone can measure the diameter of the bullet where it just enters the case.

No need to pull the bullets as they would be “squished” due to the loading process.

I don’t think miking the bullet at the case crimp will give a useful figure, as W&M have two figures, the .355 for bullet max and .353, as I recall, for the bullet at the case mouth. Jack

Donnelly’s book gives a bullet diameter of 0.360" and a cartridge OAL of 1.181". I doubt that manufacturing tolerances on OAL would be much better than +/- 0.01", especially under wartime conditions.

From the description of your experience, use of a lead bullet diameter >0.356" is indicated.