Japanese Type 91 Modified

[strangms]

Hi Guys,
I was wondering if anyone else has one of these Japanese Type 91 Grenades
That has been modified to be used as a hand grenade and not for use in the knee mortar?

The Japanese modified these by changing the fuse to a shorter delay; doing away with the booster and smoothing the bottom were the treads were. The bottom of the grenade was painted white. The fuse and fuse cover tends to have a purple tint to it.
Also they put some welds at the top and bottom so it would not go in a knee mortar tube.
There seems to be different types of welds.

strangms

 

[Slick]

Interesting. Never noticed THAT before. I will check the one I have left, but I don't recall the weld spots being evident on any I've seen. Anxious to see what else ya got.

Rick.

 

[Trenchwarfare]

I have one, that still has the recess, for the booster, but is not threaded. It also has the applied solder. Most of it. When I got it years ago, I thought is was part of some trench art at one time. So, I flicked a piece of the solder off with my fingernail. For some reason, I left the rest. Guess it wouldn't come off, with the fingernail. DUH!!! Told you, this was a great site.

 

[Grenademan2005]

But in fact it was no necessary to do all that work, just take the original grenade and throw it by hand. Maybe those modifications were done for another purpose.

 

[Trenchwarfare]

The modifications had nothing to do with throwing. They were to prevent use in dischargers. I assume due to the different type fuse.

 

[strangms]

I agree with Trenchwarfare, I think it was done so they wouldn't be dropped into a mortar tube. That would not be good with no booster and only 5-6 seconds on the fuse.........

In fact, we have tried one in a knee mortar and it would not go down the tube.

strangms

 

[Kilroy was Here]

The modifications had nothing to do with throwing. They were to prevent use in dischargers. I assume due to the different type fuse.

Yes, this was the reason. The delay in fuzes were different.

 

[wichitaslumlord]

I also have one with the solder strips on the bottom only. It has the booster recess but it was never threaded. The newer bodies have no booster recess at all so this may have been a way to convert older bodies designed for use with a booster into "hand thrown only" until the supplies were exhausted. The solder was insurance against an enterprising soldier jamming a booster into the recess and using it in a knee morter (or cup discharger without the booster). Would the setback of firing even actuate this shorter delay fuse? Jeff? Jim? Frank? Pat

 

[paul the grenade]

heres one i have.
it has 6 blobs of solder on bottom and looks like the threads on the base hole have been bored out.
Cheers, Paul.

 

[US-Subs]

I also have one with the solder strips on the bottom only. It has the booster recess but it was never threaded. The newer bodies have no booster recess at all so this may have been a way to convert older bodies designed for use with a booster into "hand thrown only" until the supplies were exhausted. The solder was insurance against an enterprising soldier jamming a booster into the recess and using it in a knee morter (or cup discharger without the booster). Would the setback of firing even actuate this shorter delay fuse? Jeff? Jim? Frank? Pat

Correct - as Kilroy stated, its all about the fuze delay. They converted the old bodies to grenades and painted the bases white for identification of the converted munitions. The much shorter delay did not allow for safe firing from the dischargers, so the welds were added to prevent their entry into the barrels.

I've never actually thought too much about how the dischargers were functioned, I would have thought that the Type 91 fuze was whacked - like a 99 or 97, then the piece was dropped in the tube and sent on its way. I seriously doubt that the setback was enough to reliably function the fuze otherwise, there simply isn't enough mass for setback - for it to do so would mean a pretty sensitive fuze. I'm sure it's explained in one of the mortar books, I've just never read it.

 

[Trenchwarfare]

Type 10, and 91 fuses were activated by forward inertia, during the firing process.