Why is it that tank guns were so small before WWII? Most were around 37-47 mm and the barrels were rather short. By the end of the war, guns were around 75 mm in size. What changed and why weren't those changes implemented earlier?
Small tank guns?
- Thread starter Shtudmuffin
- Start date
You have to remember that tank-vs-tank combat had been quite rare prior to WW2. Even in WW1 it had only happened a few times. Therefore there was little realistic idea about what it would be really like. Then you also have the problem of the role that a tank would play on the battlefield - to support the infantry or attack any enemy tanks (this was especially true here in the UK, where we had I tanks (I = Infantry) and C tanks (C = Cavalry). Big guns weren't really seen as being needed at first. Of course as the amount of experience gained by everyone increased, a lot of very hard lessons were learnt.
You had two types of tank guns. Anti-tank guns which had to have a lot of kinetic power to punch through enemy armor, this were the small calibre guns, long barrel giving them enough energy to do what was required of them. Then you had anti-infantry guns which had to be big so they could pack a lot of explosives and could do serious damage, those were large calibre guns. So you had two guns and two types of tanks. Pz III was anti-tank, Pz IV was anti-infantry.
It wasn't until later (1943ish) that you get guns that could do both, have large calibre for AI rounds and create enough energy for AT guns to be effective, thus creating a new class of main battle tank which could do both jobs. Multi gun tanks, AI and AT, were mostly failures.
It's worth noting that US resisted Sherman Firefly upgrades because they thought it will only marginally improve their AI capability, which was seen as main task for their tanks, tanks would be handled by SP AT guns.
And it's also worth noting that IS series of Soviet tanks were designed with AI in mind, though the sheer ammount of explosives in round could knock out most German tanks even if round sucked at AI.
It wasn't until later (1943ish) that you get guns that could do both, have large calibre for AI rounds and create enough energy for AT guns to be effective, thus creating a new class of main battle tank which could do both jobs. Multi gun tanks, AI and AT, were mostly failures.
It's worth noting that US resisted Sherman Firefly upgrades because they thought it will only marginally improve their AI capability, which was seen as main task for their tanks, tanks would be handled by SP AT guns.
And it's also worth noting that IS series of Soviet tanks were designed with AI in mind, though the sheer ammount of explosives in round could knock out most German tanks even if round sucked at AI.
Riain
Banned
The turret ring dictates how much turret a tank will carry and therefore how much gun. Turret ring size is dictated by hull size and prior to WW2 hull size was dictated by the loading gauges of railways. The loading gauge in Germany being bigger than in Britain which is why early German tanks got upgunned and kept their 3 man turrets but the 6pdr in British tanks came at the expense of the 3rd crewman.
Later in the war countries got around the train thing, they had to to build bigger tanks with more powerful guns.
Later in the war countries got around the train thing, they had to to build bigger tanks with more powerful guns.
Although some designs were still constrained by their transport method. ISTR that the Sherman kept its relatively low-velocity 75mm partly because it allowed the tank to fit neatly into a landing craft. More capable guns were available, but their use in the Sherman had to wait until the landing craft factor was not an issue.
Same track gauge, different loading gauge: http://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/loadgauge/loadgauge.htm
Riain
Banned
The loading gauge isn`t the distance between tracks; it`s the minimum clearence of bridges, tunnels, station platforms, power lines, signal gantries and other crap that hovers around and above a train line. Apparently in Britain this sort of thing encroached more into the space a train could occupy than it did in Germany. Of course there are many fine lines where this isn`t a problem, but a single narrow tunnel can throw out a mobilisation schedule if not properly addressed.
Yeah. And while the difference isn't that significant between Britain and continental Europe (or the USA), it is there.
So this raises a question. Why did this cause an issue early on? As in, why were the changes that made it not such a big deal not made sooner?
Riain
Banned
You sneako`d me, but that shows it perfectly, a German tank could be ~8% wider than a British tank because German railway infrastructure allowed that extra clearence. So turret rings could be 8% bigger and therefore carry bigger guns, up to the limit of 50/L60 and 75/L46.
In the case of Britain, weren't there also some inter-army politics involved, in that given the tight inter-war budgets, the Royal Artillery wanted to keep a monopoly on firing useful HE rounds & any SPGs because if tanks were given guns big enough to fire useful HE rounds, the RA feared that that would be the wedge the Royal Armored Corps would use to greatly expand itself at the expense of the RA & arrogate much of the artillery's mission of firing HE rounds to destroy enemy targets?
Riain
Banned
I think it might have been the USS Midway scenario with tanks, the Midway gave up the strategic advantage of being able to transit the Panama canal in order to gain the tactical advantage of a much larger airgroup. My guess is that the tactical advantages of big tanks with big guns outweighed the fact that you couldn`t rail transport them through a large number of places. I imagine there are ways and means around this, not all railway lines run through tunnels and other restrictive things so they`d route trains away from these places, and maybe make more use of trucks or river barges or whatever. What`s more by mid war it became obvious what the strategy and enemy was, so you could discount many of the scenarios that pre-war planners who designed tanks had to think of.
Makes sense. And if the early scenarios aren't expecting big tanks to be necessary . . .
Oh yes. Empire-building at its finest. Professor Parkinson could have made far more examples of administrative insanity than the "number of warships/number of employed at the Naval Department" equation.
Another problem was resistance from the officer corps in many countries. They didn't want to become mechanics, trapped by maintenance regulations or logistics. And they did definitely not want to be commanded by officers of that kind, so they did their best to kill/delay all forms of mechanized warfare, combined arms and "scientific warfare".
A third, very British, problem was the mental divide between "cruiser tanks" and "infantery tanks" with totally different roles and weapons.
I don't think we can say that was a uniquely British idea. As mentioned earlier in the thread, the Panzer III and Panzer IV were another example of that sort of thinking - consider the differences in armament there.
A good example of a similar philosophy is the Grant - a 75mm gun in the hull for infantry support, and a 37mm AT weapon in the top turret. That's combined in the same vehicle, of course, but there weren't many truly multi-purpose weapons early in the war.
The Sherman Firefly fitted onto landing craft, as did the US Sherman with the 76mm gun. The Sherman kept its 75mm due to inertia in the AGF which believed that the gun was adequate and did not listen to reports from the field that suggested that the Sherman needed to be up-gunned.
The US could have fielded 76mm armed Shermans much earlier and they also had the option of following the example of the 57mm AT gun, which was basically a British 6pdr modified to US standards (the US Army did field a very small number of Fireflies near the end of the war).
But the Panzer IV could move as fast as Pz III and was more of an assault gun than an infantry tank. Pz III/IV had a difference in weapon and targets but were used in the same formations, while cruiser/infantry tank also had a difference in tactical use and units. And both german tanks had (or were prepared to carry) fairly big guns, compared to Mathilda 1 and Mathilda 2.