WW1 Japanese Line throwing cartridge info needed (Mark B Grenade Rifle variant)


I need to find out what cartridge was used in this extremely rugged line throwing gun, probably naval rather than commercial use. Cartridge is probably similar to .45-70 as it is a rimmed case. I cannot do a chamber cast yet, but looks like rim diameter will be .650" - .700’ and the bore diameter is about .445". This fires a very heavy projectile weighing 880 grams or a little over 1 pound 15 ounces. The projectile is a solid steel rod which fits into the bore about 15 inches, with a steel head with a shroud that slips over the outside of the barrel for about 6 inches. This does not appear to be any sort of whaling projectile, but strictly for line throwing purposes. The extreme weight of the projectile justifies the overly thick stock and massive steel buttplate intended to be placed against a solid structure, not shoulder fired.

It was supposed to be a souvenir brought to the U.S. after WW2.

Any help on identifying the cartridge would be appreciated. And, any info about the model designation for the gun itself would also be appreciated. The action is similar to a Type 38 or Type 99 but purpose built with a solid receiver bottom, not cut for a magazine.
I apologize for the lousy photos, but they at least give an idea of what the gun looks like.





Hi John, it is a Mark B grenade launcher. I don’t think I have ever seen any documentation describing the propelling cartridge, but tomorrow I’ll check a few references.




It’s just a guess but the Japanese No.30 (30 ga.) seems to fit your rough dimensions. Is the chamber straight walled or bottlenecked?


I think it will be chambered for 11mm Murata.
I had a reference book which covered the grenade launchers and that might have some information on similar arms, but I cannot find the book at the present time.

If you post your question on the Firearms of the Rising Sun forum on Gunboards, one of the Banzai members will probably give you the information you need. http://forums.gunboards.com



I just checked Babich and Keep’s book on Japanese grenade rifles and launchers -with Bill Woodin’s collaboration- and there is no information about the cartridge used in the Mark A caliber 12 mm (converted Type 18) or Mark B caliber 11.3 mm (specially-made Type 38 action). There is no mention of a line-throwing accessory.




Fede and tanegashimatomurata- Thanks very much!
This is nearly identical to Japanese Mark B Grenade Rifle (using a special type 38 action) as shown in the Babich book, identified as being used in China and Siberia during WW1. The book notes that the grenade launching cartridge specifications are not known, but I agree that a variant of the 11mm Murata or 30 Gauge shotshell are probably the cases used. I need to do a chamber cast to see if it is a necked cartridge or straight taper.

This gun differs from the Grenade Rifle example shown (from the Army Ordnance Museum, presently in storage awaiting construction of a new home) in that it does not have any provision for the sight on the upper end of the barrel spring, and it has the very large canister for holding shot line. There is a small spring which holds the canister in place, and the canister is easily removed and replace for storage or carrying.

The projectile and canister appear to be contemporary with the rest of the gun and definitely made specifically for use on this type of gun for line throwing use.

Although the 1 pound 15 ounce projectile weight is much heavier than typical rifle type line throwing guns, it is lighter than the 2.2 pound grenades, illumination or smoke projectiles used on the Grenade Rifles, and those achieved a range of 320 meters (350 yards). Range for line throwing would probably be comparable with the same launching cartridge since the drag and weight of the line would probably decrease the range while the lighter and more aerodynamic shape of the line throwing projectile would increase the range.
If anyone has any Japanese cartridges approximately 11mm by 60-75mm length loaded as blanks they may be for these guns. Any diemensions on those would be appreciated to compare with chamber dimensions when available.


Thanks you!

I need to get some better photos before posting there.  Fede's

suggestion on the Babich book was good, and although I had a copy I
never thought to look there as I only remembered it covering the
Knee mortars and rifle attachment types.




The case on the left I have always thought was an 11mm Murata case with the neck blown out to re-use in a No.30 shotgun, but maybe it could have been a blank for use in a grenade or line launcher? It would be too long to chamber as a blank in the 11mm Murata.

Left to right:
55.7mm case length, 13mm case mouth, meiji 18 headstamp
59.1mm case length, 13.3mm case mouth, no headstamp
59.8mm case length, 13.5mm case mouth, no headstamp
74.6mm case length, 12.7mm case mouth, no headstamp
59.7mm case length, 11mm murata, meiji 23 headstamp

These cases all came direct from Japan.



I will not be able to get a chamber cast made until sometime next month, but will post results when available. THANK YOU!


I finally got a chamber cast done and chamber dimensions are below and cartridge should be slightly smaller:
Rim diameter- .715" or 18.2mm
Base forward of rim- .635" or 16.1mm
Shoulder dia.- .597" or 15.2mm
Neck dia.- .447 or 11.4mm
Bore dia.- .447 or 11.4mm

Length from front of rim to shoulder 2.400" or 61.0mm
Length from front of rim to front of shoulder 2.800" or 71.0mm

There is a definite shoulder in the chamber.
The neck diameter is the same as the bore, but since no bullet was used to propel the rod type projectile, only something to retain the powder in the case was needed, either a card type wad or a crimp.
This may have used a straight walled case that only fills the chamber to the beginning of the shoulder. Or, it may have used a case with a tapered end, or a common shoulder and a neck.

It is possible that any of the first three cases with 13.0-13.5mm mouth might have been used, with a large wad which was simply compressed with fired in the 11.4mm bore and the “neck” in the chamber is nothing more than a forcing cone. (What looks like it may be the end of the chambering for the neck is just a break in the chamber cast material and not a change in diameter.)

With these new chamber dimensions, are there any other possible matches from Japanese cartridges either known examples or in publications?


Did you try to chamber some shotshell cases and see if one could fit?


Sorry, I do not have any cases anywhere near this size.


John, excellent information, thank you very much for sharing.