Knee mortars vs rifle grenades in ww2

#1
In the second world war Japan was famous for producing a very unique weapon that was built like a mortar and can fire grenades called the type 89 grenade discharger often called the knee mortar. How did it compare to the rifle grenades of its day like the m7 rifle grenade launcher the US was using?
 
Jul 2016
9,311
USA
#2
Type 89 knee mortar had much better range than any WW2 rifle grenades, but was bulkier. The benefit of the rifle grenade was that only a small attachment to the muzzle, some blank cartridges, and the grenades themselves were needed, so any rifleman could, in theory, carry it. The knee mortar was 10 lbs alone, a separate weapon to be carried.

Overall, the knee mortar was better for the job of lobbing grenades.
 
Oct 2015
804
Virginia
#3
Apparently, each Japanese rifle platoon included a squad of 13-15 men equipped with 3 or 4 Type 89 "Knee Mortars". Did US Army or Marine Corps TO&E's identify men as "Grenadiers" and equip them with the adapters, blank cartridges and rifle grenades, or was it handled informally?
 
Jul 2016
9,311
USA
#4
Apparently, each Japanese rifle platoon included a squad of 13-15 men equipped with 3 or 4 Type 89 "Knee Mortars". Did US Army or Marine Corps TO&E's identify men as "Grenadiers" and equip them with the adapters, blank cartridges and rifle grenades, or was it handled informally?
Both US Army and Marine Corps had dedicated grenadier positions inside their rifle squads. Both also had 60mm mortars assigned to the company level, which were more effective than the Type 89, though not as available (which was a benefit of the IJA, whose platoon commanders had more firepower he controlled). Captured Knee Mortars were popular to use, but ammo was always a problem, either resupply or else faulty rounds that might blow up the gun. Early in the war, after the M1 Garands were issued they didn't have an adopter for launching grenades so grenadiers were still issued M1903 rifles up until I think around '44 when the Garand grenade launcher adopter was issued out. This remained standard for a few decades afterwards (the US Army and Marines didn't greatly change organization or arms of the infantry until the very late 50 into the 60s). Immediately post war, after doing operational research of combat, the US Army really wanted to go with a single weapon that had the ability to fire on very controllable full auto chambered in a small-caliber, high-velocity (SCHV) caliber, and with a grenade launcher attached (Project SALVO), which never panned out. They didn't even get a dedicated grenade launcher until the 60s, with the M79.

IJA in WW2 did things a bit differently than the US with unit organization. For instance, they didn't even have rifle squads. Every squad was considered a LMG squad (the Germans were far from the only ones who heavily relied on MGs in their squads), and was based completely around their version of the Czech ZB vz. 26, they called their versions the Type 96 (6.5)/99 (7.7) light machine guns.

Crazy bastards put bayonets on their LMGs too. :lol:
 
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#5
Type 89 knee mortar had much better range than any WW2 rifle grenades, but was bulkier. The benefit of the rifle grenade was that only a small attachment to the muzzle, some blank cartridges, and the grenades themselves were needed, so any rifleman could, in theory, carry it. The knee mortar was 10 lbs alone, a separate weapon to be carried.

Overall, the knee mortar was better for the job of lobbing grenades.
Well ideas watching a video about the knee mortar from gun Jesus and he said the mortar can fire regular grenades about 190 meters or so. Yet I found an instruction manual for the m7 grenade launcher and it asserted the that it can lob agrenades to about 225 feet which is over 200 meters
 
Jul 2016
9,311
USA
#7
Also wasn't the 60mm mortar a much more heavier weapon that needed a dedicated team? So it was a lot more difficult to lug around and use
Yes. 60mm M2 mortar was heavier, bulkier. And while it can be fired "off-hand" it was most commonly fired off a bipod and larger base plate by a team of at least three men. However, because of that bipod and base plate, it had repeatability that the knee mortar did not, so multiple rounds can be fired fast and all with hit inside a "sheaf", a specific distance of one another. So accurate. And because of that repeatability, adjustments were easier to make (Left 200, Add 500, fire for effect). What this means is concentration of fire. Add in a mortar squad leader with binoculars, maybe some radios between the mortar squad and the platoon leaders up front (who had radios too), they could plant mortars just behind the main line of resistance and start dropping rounds.

Whereas with the Type 89 "knee mortar" grenade discharger (not actually a mortar), each round would have to be aimed separately and there was little ability of a concentrated fire mission, or good accuracy. It was an area fire weapon. But more mobile. So a trade off.

Meanwhile, the Japanese infantry didn't have an actual light mortar at the company level, nothing similar to a M2 60mm, the smallest was the 90mm mortar, allocated at the regimental level or separate fires companies or battalions that could be attached to a regiment.
 
Jul 2016
9,311
USA
#8
Well ideas watching a video about the knee mortar from gun Jesus and he said the mortar can fire regular grenades about 190 meters or so. Yet I found an instruction manual for the m7 grenade launcher and it asserted the that it can lob agrenades to about 225 feet which is over 200 meters
225 feet is under 100 meters. A meter is roughly 3.3 feet.

I'm not expert in rifle grenades, but the max range was very dependent on the model, the round, and the blank used. Regular blanks, like those used in training, didn't have enough power to launch them far, they needed a special blank with lots more powder in it (which is why the rifle grenade kicked like a mule).
 
Jul 2016
9,311
USA
#10
Sorry I meant yards not feet. Still I guess a rifle grenade would be harder to use than a dedicated grenade launcher
Really depends on the type. And the munition. The Type 89 grenade dispenser has greater range and the rounds had more explosive power than most WW2 era rifle grenades. But there is the trade off. Grenadier armed with a rifle grenade doesn't need to haul a rifle, plus spare weapon, with a team of numerous men to supply ammo. He carries it all on him, and only needs to afix the launcher, load the grenade, reload with the blank, and then can fire. He also has the ability to use other sorts of munitions, and the early war AT grenade wasn't horrible, so it gave a way for a standard squad to deal with light armor without needing to resort to a bazooka, or to using handheld weapons (mines, grenade bundles, satchel charges, molotov cocktails, etc).

Overall, I'd say that the knee mortar would have been nice to have in the infantry platoon, in certain circumstances. In others, it was a waste.
 

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