Hi guys, thanks for tuning in to another video on ForgottenWeapons.com.
I'm Ian, I am here today at the James Julia Auction House
up in beautiful Maine taking a look at some of the guns that
are coming up for sale in their October of 2015 auction.
And I wanted to start out with this very cool Japanese
sort of mortar, sort of grenade launcher.
Now something I personally have been looking into a lot recently,
and I think a lot of other people have as well, is World War One.
Obviously we're in the centennial of World War One. And
if you look at the trench fighting in World War One,
one of the things that most militaries in the world
learned from it was that having a light explosive projectile
indirect fire weapon, a trench mortar,
was a very valuable tool for a lot of troops.
It was capable of doing a lot of things, it really filled this gap between where a machine gun was useful
and where proper crew-served artillery was useful.
Now the Japanese of all people actually came up with really one of the best
iterations of this type of weapon, and that is colloquially known as the "knee mortar".
To the Japanese this was the Type 89 Tekidantō. It was considered a grenade discharger.
It's actually kind of in this weird zone where it's not really a mortar because this actually has a rifled bore.
But it's not really a grenade launcher because, while it can use modified hand grenades,
it's typical projectile was actually a specialty propelled unit.
Not quite a grenade more like a mortar shell, but not really a mortar more like a grenade launcher.
So I want to take a closer look at this, but I want to start off by pointing out that the Japanese made a lot of these.
They introduced them in 1929, they made about a 120,000 of them in total.
And they equipped troops with these in almost the same numbers as light machine guns,
so this was a very important weapon to be used by Imperial Japanese Army tactics.
The idea was you could use one of these guys very much like a light machine gun.
The guys who had these would use them to fix an enemy unit in place, keep their heads down, keep them
basically under a suppressive fire while a second unit of riflemen or light machine gunners,
or another unit, manoeuvred to get into a flanking position.
So very much the way the Germans would use a general purpose machine gun
to hold a unit down while riflemen manoeuvred to expose it.
That's how the Japanese used these knee mortars.
Now I should also point out the ... name "knee mortar" is of course an American thing.
I've seen some speculation that the term actually came from the Japanese description for the carrying bag for these
which went on your leg and could be mistranslated as a knee bag for a mortar. Maybe that leads to the name "knee mortar".
The most common understood origin of the name is this curved butt plate on the weapon,
which a lot of US troops, this is how the story goes, US troops thought,
"Ah, you that on the top of your leg and then you fire it." And if you do that
I'm sure it feels fine until you pull the trigger on the thing, and then it breaks your femur and does serious damage.
From reading World War Two US GI accounts, the guys weren't stupid enough to do that.
Frankly, any GI who had fired a rifle grenade from their shoulder knew that
something this big and heavy out of a weapon like this, you did not want to have on your leg.
And I don't think that happened very much despite the stories about it.
The idea for this curved base plate was to allow you to dig it into soft ground,
or fire it from things like roots, trees, logs, whatever happened to be around.
This was a very flexible and very quick to use weapon.
So why don't we go ahead and bring the camera back here,
and let's take a closer look at how exactly this thing worked, because it's really quite clever.
So there are a couple elements that really distinguish this guy, the Type 89, from a typical light mortar.
The first is that it has a rifled bore.
Should be able to see that, yeah, you can see the rifling right in here.
A typical mortar does not have that.
The other thing that differentiates it is that this is actually ... the equivalent of a closed bolt gun rather than an open bolt one.
Typically a mortar will have a fixed firing pin down at the bottom of the tube,
and you'll have a primer on the base of your mortar shell, which this did.
The primer on this one would be in the middle, it's gone, this is a deactivated shell.
But typically what you do is you drop the shell down the tube and it slides down.
When it hits the bottom that primer fires and it launches the shell.
And in order to aim a mortar what you generally do is you have a pair of legs coming off the front,
and you adjust the angle of the mortar to where you want to fire.
The Type 89 did this totally differently. Instead it has a range adjusting dial right here.
... You can see as I turn this dial this assembly moves up and down (that's actually the trigger).
And there are two scales on it, so you could fire a standard Japanese issue hand grenade
that you could screw a propelling charge to the bottom of. Those had a range of approximately up to 190 metres.
That's what the scale goes up to here, from 40 out to 190. So you know that's not too bad.
However if you used the purpose-built Type 89 projectile (these are 50mm by the way),
if you use the Type 89 your range actually goes all the way up to 650 metres.
That's quite a significant distance, that's definitely light mortar territory, that's beyond rifle grenade.
Anyway, in order to change the range you adjust this dial,
and what you're doing is actually moving the firing pin inside the bore.
So I can bring it up, in fact I'll do that, let me bring it up all the way.
Then to fire the weapon, you put it down, you put the projectile into the mouth.
Now because I've got this set to a very short range, this would be 55 meters,
the projectile is just barely sitting in there. Which means the firing pin is right about here,
and we have this very large expansion chamber for the propellant gases.
What that means is when I fire it not much pressure is generated,
this comes out and just kind of goes plop about 55 meters away.
If I expand the range,
let me leave the projectile in there so you can see this, as I lengthen the range you can see that drops down the bore.
Once I'm all the way at the bottom, now I have a very small volume of combustion chamber.
So when I fire the grenade a lot more pressure is generated, the thing goes a lot farther.
This is
(take that out),
as I said, this is our trigger. It's spring-loaded, it's double action, it's actually very stiff, which was typical on them.
Often you'll see these with a little leather lanyard so that you could get a better grip on it.
On a typical mortar you adjust the angle of the barrel to adjust range.
Since we're adjusting range on this through our little threaded adapter here,
instead you always fire this at exactly a 45 degree angle.
In order to ... make sure that you're doing that correctly, it has this bubble level clamped to the barrel.
Now the bubble level's down because I'm actually pointing this slightly down right now,
but there's a little line right there, and when you're at 45 degrees
there's a little level indicator in the bubble ... that sits right on that line, confirms you're at 45 degrees.
You then use this groove on the barrel as your sighting line.
Line up, fire.
These were particularly effective weapons because they were so light,
the whole assembly is only about 10 pounds, so it's about the weight of a rifle.
They were carried by men right at the front lines, and in almost any sort of emergency
contact, you could pull this thing out and start firing extremely quickly.
The US troops in the Pacific ... the closest thing that they had was a 60mm light mortar,
which had a base plate and a tube and bipod legs, and took significantly longer to get into action.
In fact, so much longer that American troops did actually resort to simply carrying the tube
and jamming the tube into the dirt or against a log and using it kind of like these.
However, they weren't really designed for it, and the accuracy was far less than the Japanese could get with these knee mortars.
Now the projectile itself is kind of interesting.
The front here is full of explosive charge. These ... came very close to being the equal of the US 60mm mortar in terms of effectiveness.
They have a threaded portion at the rear which comes off. This is where your propellant charge would be.
Of course this is a deactivated shell, so it doesn't have any propellant in it.
Now what's interesting, you can see there are some holes around the circumference of that base, as well as in the bottom.
The holes in the bottom vented gas to propel the grenade. The holes in the side actually pushed
propellant gas against this copper band, which caused it to expand and grip the rifling in the barrel.
You probably saw I was able to slide this in and out of the barrel without any resistance,
that's because it's actually under-sized until you fire it. At which point this expands so that it can [??].
The fuse on these, right here, it's a contact fuse.
So pull the pin to arm it, and then when it hits something it detonates. Pretty simple.
Alright guys, since I've got this thing here I figure I should pull the table away and show you how it would actually look to use.
So I've got my elevation bubble here.
I'm going to run this up to a fairly close range, so I'm not dropping the shell way down.
Let's say we have an enemy at 75 metres.
So what I want to do is run it to right about there, bubble level says I'm at 45 degrees.
Drop my shell in.
Use this line on the barrel to check my aiming point, and then, boom, fire the weapon.
Again, I have a good eye onto my level right there,
drop the shell in, fire, and away you go.
All you have to do to repeat is take another shell,
drop it in, line up, fire.
These were very fast and very effective weapons, especially in the jungle.
Now something else to point out.
These were also used in a direct fire role, when necessary, at very close range.
You could put this up against any sort of horizontal structure, surface, block, whatever,
and use them to actually fire through, say, windows of buildings, or ports in pillboxes,
anything like that. That was also used.
Well, thanks for watching guys, I hope you've enjoyed the video.
This is of course for sale. This is an NFA weapon, it is classified as a destructive device
so you do have to do an NFA transfer on it. But it's coming up for sale here at Julia in October of 2015.
If you take a look at the description text below, you'll find a link to their catalogue page on it.
This is a gorgeous condition one, it's one of the better ones I've ever seen.
So if this is the sort of thing that you'd like to have, I think this would be an excellent one for you to take a closer look at.
Anyway, I hope you enjoyed the video, learned something new.
Tune back in again, we'll have some more cool stuff coming up from the Julia auction.
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