What is the difference between anti-tank guns and self-propelled artillery?



Why can’t I just aim the artillery down or the anti-tank up? Why do they have to be different guns?

In: Engineering

These terms are not mutually exclusive. An anti-tank gun is a form of artillery designed to destroy tanks. Self-propelled artillery is an artillery piece that is combined with some sort of vehicle mechanism that allows it to move on its own.

You can certainly have both, most notably Tank Destroyers.

You technically could make just one type of gun that do both, we in the past, because today anti-tank gun isn’t really a thing anymore, they were replaced by missile, rocket propelled gun and stuff like that, but let’s talk as if we were in WW2.

You could build just one gun to do it all, but it wound’t be that good, you still need people with different training, different ammunition and those guns would be way too expensive for no reason.

In general an artillery piece was bigger and longer than an anti-tank gun. Most artillery were 105mm with 75 as light artillery and some going up to 150mm or even 240mm. The reason is that you need a lot of space in the shell for the high explosive. Anti-tank gun usually want a smaller caliber that goes really fast to penetrate tank. So it was more like 37mm, 50mm and later 75mm to 90mm. Some were bigger, but in low numbers. If you use a 105mm gun for artillery and anti-tank, you won’t be able to produce enough to equip all your unit. A 105mm anti-tank gun would be powerful, but overkill for most of the tank people faced in WW2, especially in the first half of the war.

On top of that, indirect fire and direct fire can use the same gun, but not the same surrounding system. If you gun can do both, it need a bigger mounting system that is able to change the elevation of the gun by a lot more, you don’t need that in an anti-tank gun, so that’s added cost which result in less unit produced. Same with optic, how you target will be different in direct and indirect fire and so you need two system on your gun instead of just 1.

It’s also about mobility. It’s a lot easier to transport a 50mm anti-tank gun and its ammunition, than to transport a 105mm artillery piece and its ammunition. For artillery you are further back of the front and usually can take more to step up your position, while the anti-tank gun should be more lightweight to move at the front and engage the ennemy, stay hidden or change position.

But even if both gun would be the same, you still can’t use the same unit for both role, because of people and ammunition. The job of using an anti-tank gun isn’t the same as using an artillery gun. You need different training. If you teach both job, your guys won’t be as good at both. On top of that they are not using the same ammunition. It’s simply easier for training and logistic to have those two role done by two different type of military unit.

Self Propelled Artillery is generally something like the [M109 Howitzer](https://en.wikipedia.org/wiki/M109_howitzer) where its a gun mounted to a motorized chassis while Anti-Tank guns are generally portable but not self propelled. The main differences between them is how far up and down the gun can go.

In some scenarios they have been exactly the same gun just sporting different ammunition. In WW2 the Germans used the 88 mm guns to great effect in a variety of roles. It began as the 8.8 cm Flak but was later turned into the 8.8 cm KwK and 8.8 cm PaK which were used as the main cannons on Tiger tanks and their heavy tank destroyers. Load a high explosive round and you’ve got yourself artillery, load a time high explosive round and you’ve got an anti-air gun, load an armor piercing round and you’ve got an anti-tank gun

In general though, once mounted onto a self propelled vehicle a gun will only serve a single purpose.

Your self propelled artillery doesn’t need to be well armored since it should be a ways away from the front, it needs to be a stable platform for consistent shots, carry a lot of ammo, and be able to get into position quickly.

Your anti-tank gun is going to be mounted in one of two ways. In a tank destroyer its going to be in a big vehicle mounting lots of armor so it may not be in a full turret which can point up, but it will be able to take a hit. The other option is a gun motor carriage which is a truck with a big gun on it that can shoot and quickly scoot away because it can’t take a hit. You also wouldn’t want a turret that supports a lot of elevation on this because then you’re heavy, slow, and dead.

Military systems generally don’t want one thing that good at everything. It seems handy to consolidate your supply chains but it really messes with the designs and can make everything more expensive. Often the cheapest and fastest solution is to make one thing that good at one thing, and a second thing thats good at a second thing. Making one thing good at two things takes 3x longer and costs 8x as much.