The Army's Goofiest Light Tank Project

Ajouté : 2026-05-05

[00:00:00]When we think about World War II and armored fighting vehicles, we often turn our focus to tank-on tank engagements. I mean, it makes sense on some level, right? We want to compare contemporaries between nations and imagine how they would perform going head-to-head. It creates a huge blind spot to the fact the tanks are fighting infantry the vast majority of the time. You may have heard that some US tank units were reluctant to go to the upgun 76mm Sherman variants as their current 75mm Shermans had a more effective high explosive charge, meaning they were willing to forego the increase in armor-piercing power in order to maintain effectiveness against their primary target. However, there is a funnier and lesserk known example of this anti-infantry focus. In 1941, a collaboration between the Army Airore, Armored Force, and Ordinance Department was established to create an airborne light tank. This would eventually result in the T9, also known as the M22 Locust.

[00:00:47]The M22 is a dimminitive little tank, small enough to fit in a glider or C-54 Skymaster. With a weight of just 7.4 metric tons and a top speed of 56 km/h, the M22 has gained a reputation in the AFV history community as a goofy little specimen. Mostly thanks to tank games like War Thunder, where the M22 can be both effective and ludicrous. As you would expect, in order to make the M22 air deployable, compromises had to be made to its armor and armorament. It utilized the same 37mm M6 cannon used on vehicles like the M3 store and M8 Greyhound, which while fairly effective as an anti-armour tool early on in the war, was not especially effective against infantry. The M6 had two principally anti-personnel rounds, the M2 canister round and the M63 high explosive round. While the canister round was found to be fairly effective, especially in the Pacific, the M63 was not. The M63's bursting charge was just 38.5 grams, which for context is less than the 52 gram found in the Mark II hand grenade used at that time. American units didn't use the M22 Locust, but some airborne units in the United Kingdom did. They complained that the high explosive content of the M63 shell was so anemic they could barely even tell where the shell ended up impacting.

[00:01:57]This was a problem the Army was acutely aware of, and so the Ordinance Branch set out to find a solution in late 1943.

[00:02:03]But how could you increase the high explosive punch of such a small tank?

[00:02:06]Even if you could find a way to fit a large cannon in the turret, surely either the turret or the suspension would be unable to handle the recoil impulses. The solution of all things was to smack a mortar in the turret and use that. Yes, the ordinance branch wanted to turn a Locust into a quasi artillery vehicle. Mortars on AFV certainly aren't that uncommon, but they're usually slapped into the back of an open top carrier or built as specialized demolition mortars for engineering vehicles. The plan for the M22 was to use an 81mm mortar like you'd find a mortman lugging around on his back with some modifications to make it more suitable to use in the tank. Though, as difficult as that undertaking might sound, it was actually found to be relatively straightforward. First, you obviously couldn't have the loader getting out of the turret to drop around into the mortar tube as mortars are typically loaded. Nope. A breach loading mortar would have to be used. The problem though was that such a thing didn't exist in the US Army's artillery arsenal. That is unless they could find a way to mount the breach loading 1891 M1 coastal defense mortar on an M22, which honestly seems like a bit of a stretch. Obviously, this mortar M22 project was of low priority because it wasn't until August of 1944 that the order was actually given to design a breach loading mortar. The design work for the breach was carried out by the artillery development division of the cannon branch with the pilot model of the mortar being built by the Mosler Safe Company based out of Cincinnati, Ohio. The worst of the three C's. If you're wondering like I was, no, the Mosler Safe Company isn't still around.

[00:03:26]They kind of are, but they went bankrupt and were purchased by Diebal Nixorf Incorporated, who is still around and does still make safes. Anyway, with that tangent out of the way, the breach was of the interrupted screw type, which are commonly used on artillery pieces and large naval cannons. In fact, the Army's current artillery system still uses an interrupted screw breach. There was one major problem noted with the mechanism in that it wasn't possible to position the mortar shell in such a way as to be certain the firing pin could connect with the base of the round. This defect was eventually corrected and the mortar was shipped to Rock Island Arsenal. The second necessary development was a way to handle the mortar's recoil. It was believed that the trunions of the M22's turret would not be able to handle the recoil impulse of even the 81mm mortar, at least without some kind of recoil mechanism. The army, specifically Rock Island, already had considerable experience with designing and manufacturing concentric recoil mechanisms, which were widely used on tanks. So, it was decided the mortar would use a concentric recoil mechanism as well. With the recoil mechanism in the testing to make sure it worked complete, the T24E1 81mm breach loading mortar was shipped to Aberdine Proving Ground for more testing. The third issue that the ordinance branch needed to solve was how to deal with K. Unless you're a tanker, artilleryman, or an armor enthusiast, you probably only know Kant is a contraction of cannot. But can't is another term for an inclination or slope. Specifically, if a tank or artillery piece has to account for K, it is accounting for the offset in aiming that the sloped ground it is sitting on produces. This is less of a problem if you have a high velocity shell like armor-piercing discarding Sabo. But with lower velocity shells such as artillery rounds, the effect is much more drastic.

[00:04:56]With the T24E1 mortar, everyone involved in its development knew that K would drastically affect its accuracy. So, a solution was developed. A mechanism composed of a series of linkages, gears, and a rotating front was created that would allow the gun to remain level regardless of the slope the M22 was sitting on, provided that the crew leveled the gun manually prior to engaging the system. Obviously, all of these changes necessitated a redesigned turret. Unfortunately, there are no drawings describing what the redesigned turret looked like, but we can of course imagine that the gunman lit in relevant systems looked very different. Two different sets of figures are given for gun depression and elevation, 10 to 90° and 0 to 81°. We do not know which set is more accurate. We do know, however, that the ammunition stowage was redesigned to accommodate mortar rounds.

[00:05:39]Speaking of ammunition, we should probably go over what the T-24 E1 would fire. The mortar test fired and likely would have used the M43 A1 and M56 mortar shells. The former was a lighter shell that had a filler of 585 g of compa, which is equivalent to about 778 g of TNT. That is 20 times the H filler of the M22's original H round. But remember that's the light mortar round.

[00:06:02]The heavier M56 had 1.96 kg of pure TNT.

[00:06:07]Around 51 times more H power. But I did omit one of the T24E1 shells or proposed shells I should say. The ordinance department sent a request to the cannon branch asking them to develop a shaped charge round for the mortar so that the M22 could still engage tanks if it needed to. So yeah, you can probably see why I think this project was a little silly. Of course, there is a reason I keep saying words like proposed and redesigned. As you can probably guess, this project was very low priority. The M22 was not highly praised, being exceptionally cramped, underpowered, and produced in limited numbers. It was also exceedingly unreliable for such a small tank. As mentioned earlier, the US found it so unsatisfactory that they only used it for testing purposes and gave some to the British as part of lend lease. To be clear, this wasn't just offloading a bad product. Britain desperately needed any kind of tank after they lost so many of their own at Dunkirk. By late 1944, when the order was given to produce a breach loading mortar, the M24 Chaffy light tank was already well into production.

[00:07:04]Everything in the project took so long to get done because resources were allocated to other more important projects. One reason why the M22 was selected in the first place is that since it's so light, it was assumed that if a mortar worked in an M22, it would work in any other vehicle. A proposal was put forward to fund a pilot vehicle, but nothing came of it. and the project was canceled in mid to late 1945. The only tangible object to come from the project was the mortar itself. And while it was apparently fairly reliable during its test firings, there was obviously little need for it. While it no doubt would have been a very comedic sight to see Locust scooting around lobbing mortar shells at things, I don't blame the ordinance department for canceling the project. Direct fire guns like the 75mm and 90mm M3 had h charges that were potent enough. And with the velocity to have strong armor piercing rounds, too, using an 81 mm mortar for a tank just doesn't make a lot of sense. Anyway, that's pretty much all there is to it. I hope you guys enjoyed the video. I'm very excited to get back into making the occasional history video, especially now that I'm going directly to archived documents instead of relying on secondary sources so much. Let me know what kind of topics you guys might want to see covered, and I'll see what information I can find. Anyway, thanks for watching and I'll see you on the next