Japanese "knee mortar "

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toad
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Japanese "knee mortar "

Post by toad » Wed Mar 18, 2020 7:48 pm

https://youtu.be/dGzVZyMzDPI
Anyway , I was going through Ian McCollum's posts on Japanese weapons , and I got fascinated by the "knee mortar" . It isn't actually a mortar but a rifled grenade launcher. The curved butt plate allows it to be fired from about any surface. You can pack it down into lose dirt or off roots. It is rifled and it uses a lose copper band to enable it to be dropped down a rifled barrel and it is fired with a percussion cap gas pressure expands the copper band to engage the rifling. Actually I could see this thing still be used today. To bad it and other Japanese weapon designs suffer from NIH to an extreme. :P

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randy
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Re: Japanese "knee mortar "

Post by randy » Wed Mar 18, 2020 9:35 pm

So what advantage would it offer over the M-203 or other grenade launchers in current service?
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Langenator
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Re: Japanese "knee mortar "

Post by Langenator » Thu Mar 19, 2020 3:43 am

Probably little, if anything.

Now, if they're trigger fired, some shade-tree weapon mechanic could bolt a bunch of them together and make something like the naval Hedgehog ASW launcher, but for use against personnel...
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Greg
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Re: Japanese "knee mortar "

Post by Greg » Thu Mar 19, 2020 2:05 pm

randy wrote:
Wed Mar 18, 2020 9:35 pm
So what advantage would it offer over the M-203 or other grenade launchers in current service?
Longer range and more punch at the expense of being less accurate.

IMO the knee mortar is, like the M79/203/etc another alternative to rifle grenades.
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toad
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Re: Japanese "knee mortar "

Post by toad » Thu Mar 19, 2020 9:57 pm

50 mm vs 40 mm , practice ammo probably cheaper , like all weapons its utility depends a large part on the skill of the operator. A shaped charge round could probably be developed for it ?

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Re: Japanese "knee mortar "

Post by Langenator » Thu Mar 19, 2020 11:46 pm

You could probably make a shaped charge, but it might be less useful, because shaped charges require a direct hit to be effective, at least against armored targets. The knee mortar's lack of sights would really hamper it in anything like direct fire.
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Greg
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Re: Japanese "knee mortar "

Post by Greg » Fri Mar 20, 2020 12:44 am

toad wrote:
Thu Mar 19, 2020 9:57 pm
50 mm vs 40 mm , practice ammo probably cheaper , like all weapons its utility depends a large part on the skill of the operator. A shaped charge round could probably be developed for it ?
The knee mortar had a lot more recoil than, say an M203. You can fire the latter from your shoulder, while the former, despite weighing a bit over 10 pounds, would break your leg if you braced it against yourself. Max range was quite a bit greater. So likely projectile was quite a bit heavier too.

They were trigger fired. No reason they couldn't be used in direct fire. WAG, but I suspect with practice accuracy in direct fire would depend a lot on how well you could judge distance.....

In indirect fire one type of shell had a deliberate delay fuse so jungle canopy wouldn't set it off prematurely. Very sneaky.
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D5CAV
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Re: Japanese "knee mortar "

Post by D5CAV » Mon Mar 23, 2020 6:11 pm

I love mortars. Back in the day, the longest ranging weapons in my CAV troop were the 4.2" mortars that we carried in APCs. They could put lots of hot metal on a target almost 4000m away.

Germans in WW1 and WW2 also had "knee mortars" and "trench mortars". These, like the Japanese "knee mortars", were somewhere between rifle grenades and full-fledged mortars. The idea was to make a mortar into a single person weapon vs. crew served weapon. However, a single soldier couldn't really carry enough rounds along with the weapon to make it useful. Once you morph it into a crew-served weapon, you may as well go all the way with a 60mm or 80mm mortar with baseplate, aiming mechanism, and real rate of fire.

I don't believe the US ever fielded such a weapon. Like many "tweeners", knee mortars got lost between rifle grenades and mortars.

If a problem wasn't solved by a hand-grenade or rifle-grenade, every infantry company had a mortar section. Problem solved...
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