M37 (M4) HMC - Stop Asking

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TL;DR: An M37 HMC fitted with an M4 recoilless mortar instead of a .50 cal.


Note: This is the only picture I could find of this tank. If you have any other significant information, please let me know.


The need to motorize artillery was felt by the US military as early as WW1. Many projects attempted to satisfy this need, which was always evolving as time passed and technology improved, most failures but some successful. One such rare success was the M37 HMC, a lightweight and very mobile casemate 105mm howitzer carrier based on the chassis of the successful M24 Chaffee. In 1943, it was becoming apparent that the M3 Priest just wasn’t cutting it. It’s armament was too light for its mediocre speed and the vehicle itself was unnecessarily heavy, however, light artillery was still seen as necessary. As such, developments to mount the 105mm M4 howitzer onto a lighter and more mobile platform began. The obvious choice for this was the developing M24 Chaffee or the T24 Light Tank as it was known at the time. The finished M37 would be based on an extended M24 chassis and would share many design elements with its M7 predecessor, the most prominent of which being the “pulpit-like” machine gunner position, which would typically mount a .50 cal. The M37 would be accepted for standardized production in January of 1945, a tad too late to see service in WW2. In the spring of 1945, the US began tests regarding the mounting of recoilless weapons, which had just barely seen action and results during WW2, onto preexisting motorized platforms. The first of these tests would be simple in nature and would mount a 75mm T21 recoilless rifle in place of the .50 cal. The second test would be much more ambitious and mount mount the lesser known 4.2in M4 recoilless mortar. The new weapon was to be fired by the M37’s assistant mechanic. After undergoing firing trials, it was found that the M37’s open-topped nature severely hampered the effectiveness of the M4 its the dangerous backblast and gasses would vent directly over the fighting compartment, which could damage internal components and easily result in fatalities in a stressful combat situation. As a result, safe firing sectors were imposed, however, these sectors were not always in convenient locations for effective fire. It was eventually determined that the M37 HMC and its pulpit were not suitable to carry recoilless weapons and tests moved on.

Interesting side note about the M4 mortar: To actually function, its shells would be fitted with a rocket at their tips. When ignited, this would shoot the projectile backwards into the barrel onto the firing pin, which would then send it back out.

Place In War Thunder:

Quick derp vehicles have always had their fair share of fans. Multi-gun vehicles have always had their fair share of fans. What happens when you combine the two vehicle types? You get the M37 (M4) HMC, a vehicle with a completely unique armament arrangement when it comes to War Thunder as no current vehicle has access to a conventional cannon as well as a recoilless rifle, let alone a recoilless mortar. Playstyle would, of course, be rather unique as well. Thanks to being based on a M24, you can actually get around rather quickly and potentially show up in places where you aren’t expected. While your main weapon is bound to your casemate, your recoilless mortar is not and could potentially surprise enemies. In addition, since this is War Thunder, the safe firing sectors can be completely ignored, making you capable of defending yourself and yeeting a 4.2in bomb with 3.36kg of TNT in any direction. The best in-game placement for this unicorn is, of course, as an event or premium vehicle. It was a failed one-off testbed that only existed for a short while before being returned to its original form. It has no place in the tech tree.


Armament: 105mm M4 howitzer and 1x 4.2in M4 recoilless mortar

Dimensions: 5.49m, 3.00m, 2.77m (L,W,H)

Weight: 20870~kg

Armor: Proof against small arms fire and artillery splinters

Crew: 7


-105: Same as M4 (105) in-game (plus HESH if necessary)

-4.2: HE and Smoke

Speed: 56kph

Horsepower: 296hp

Pictures (of the M4 mortar):

Affixing The Rocket:


Rocket Up Close:






Preparing To Fire:



History of the 4.2" Chemical Mortar

M37 105 mm Howitzer Motor Carriage - Wikipedia

Tank Archives: A Fast Howitzer on a Light Chassis


Stuart: A History of the American Light Tank Volume I by R.P. Hunnicutt


Looks super fun and silly. +1

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Bring it on

The base version, without the added recoilless rifle, has very strong “We have StuG at home”-vibes.
Looks like a lot of fun though!

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