M3 Grant and M4 Sherman Family of Vehicles

[Maverick]

Tomo, I believe when the M3 was initially designed, the 37mm weapon was considered adequate as an anti-tank weapon with the hull mounted 75mm a support weapon firing HE.

Regards,

Mav

[dy031101]

With the 75mm gun in a limited-traverse mount, something's gotta be there to provide all-around firepower.  M3 is after all a (all be it interim) medium tank, not a gun motor carriage.

[tomo pauk]

Tomo, I believe when the M3 was initially designed, the 37mm weapon was considered adequate as an anti-tank weapon with the hull mounted 75mm a support weapon firing HE.

Regards,

Mav

I agree with your statement
That again questions either the perceived doctrine, or the application of the doctrine into real tanks.

[tomo pauk]

With the 75mm gun in a limited-traverse mount, something's gotta be there to provide all-around firepower.  M3 is after all a (all be it interim) medium tank, not a gun motor carriage.

Makes sense; such kind of firepower points into an anti-tank application of a tank, however.*
Hence it's again about either the doctrine, or the application of it; something doesn't follow

*my point of departure from OTL might be around mid/late 1941: US Army brass concludes that 37mm is not worth it, so they decide to build both turreted TD (=future M10), and a tank that can throw some AT punch. So they discard the turret, then try the 3in mounted in lieu of 75mm and find it a good upgrade, so the 1st such tanks are built during spring/summer of 1942. To bolster the HE performance, the new round is produced, featuring reduced charge + longer shell (idea from Russian 45mm & Bohler 47mm At guns). The weight bonus can be used to improve the armor protection.
Ideally, the M4 would've been issued with the 3in from day one

[dy031101]

Makes sense; such kind of firepower points into an anti-tank application of a tank, however.*
Hence it's again about either the doctrine, or the application of it; something doesn't follow

If you want me to venture a guess, I'd think that the doctrine led to a thinking that tanks need only to be "good enough against enemy tanks" and leave the "very effective against enemy tanks" part of the deal to tank destroyers.

[tomo pauk]

That seems to be the truth

[dy031101]

And the term "enemy tanks" probably carries different meaning between tanks and tank destroyers: for tanks it probably means "tanks of defensive nature" (medium tanks, jagdpanzers, and the likes) whereas for tank destroyers it might mean "tanks of offensive nature" (heavy a.k.a. breathrough tanks).

[tomo pauk]

The M3 APC rickshaw draw make me thinkering about the central-engined M3 medium hull turned into APC, like my M3 light APC (M4 can do the same )

[rickshaw]

Good idea about that APC.

As for doctrine (rickshaw wrote):

Of course it was.  However, the US Army still designed and ordered vehicles to fulfil that doctrinal belief

Then why going with 37mm armament for M3 medium & M3 light? Either the doctrine was not such (ie. no anti-tank work for tanks), or they were building stuff that didn't went along the doctrine 

The other countries did make 'categories', tasks, but within tank arm itself.

Why do you believe the 37mm armed tank does not fall with the doctrinal divisions?

Remember, when the M3 Light Tank and the M3 Medium were being designed, guns of ~37mm calibre were standard.   The 37mm gun both mounted was capable of firing both HE and AP.   It's the HE which is important for infantry support, not the AP.

[rickshaw]

With the 75mm gun in a limited-traverse mount, something's gotta be there to provide all-around firepower.  M3 is after all a (all be it interim) medium tank, not a gun motor carriage.

It was employed as a tank but its design was much more akin to a GMC than a tank with such a limited traverse hull mounted main weapon.

[jcf]

With the 75mm gun in a limited-traverse mount, something's gotta be there to provide all-around firepower.  M3 is after all a (all be it interim) medium tank, not a gun motor carriage.

It was employed as a tank but its design was much more akin to a GMC than a tank with such a limited traverse hull mounted main weapon.

Really? So I guess a the Char B1 was really a Yank-style GMC?  Well gollee, will wonders never cease.

[Maverick]

No, the Char B1 was a dinosaur that had no place on the WW2 battlefield.  It was a hangover from the shortsighted attitudes towards warfare from WW1, like many French armoured designs in that pre-early WW2 period.

One could suggest that the M3 was equally so, but that was also part of US armoured doctrine of the time that was essentially still fighting WWI.

Regards,

Mav

[tomo pauk]

...
Why do you believe the 37mm armed tank does not fall with the doctrinal divisions?

Remember, when the M3 Light Tank and the M3 Medium were being designed, guns of ~37mm calibre were standard. The 37mm gun both mounted was capable of firing both HE and AP.   It's the HE which is important for infantry support, not the AP.

Let me put it this way: if a tank receives both the HE & AP ammo, that means it's supposed to engage both the 'soft' and armored targets. Further, that either means that current doctrine is not against usage of tanks to fight enemy tanks, or that someone at high place is working on it's own accord (= not following the doctrine). The second choice seems unlikely to me

As for small caliber guns being standard, France, Germany and USSR (= main continental powers) designed & fielded tanks with 75mm class gun well prior mid 1940 (Char B1, Pz-IV, BT-5A/7A). That points out that small caliber guns (even the Soviet 45mm) were way underpowered for infantry support.

[rickshaw]

...
Why do you believe the 37mm armed tank does not fall with the doctrinal divisions?

Remember, when the M3 Light Tank and the M3 Medium were being designed, guns of ~37mm calibre were standard. The 37mm gun both mounted was capable of firing both HE and AP.   It's the HE which is important for infantry support, not the AP.

Let me put it this way: if a tank receives both the HE & AP ammo, that means it's supposed to engage both the 'soft' and armored targets. Further, that either means that current doctrine is not against usage of tanks to fight enemy tanks, or that someone at high place is working on it's own accord (= not following the doctrine). The second choice seems unlikely to me

OK, let me put it this way - the British Mathilda II had a 2 Pdr gun.  It was an "I" or Infantry tank - designed to be heavily armoured and to accompany infantry in the assault and facilitate their capture of their objectives.  It carried no HE until 1943 (in Australian service, the British never carried 2 Pdr HE in their Mathildas).

To us, it appears inexplicable that someone would not provide a HE round to a tank who's sole point was to support infantry but British doctrine was that the role of the Infantry tank was to use its MGs to support the infantry and its main gun to protect them from other tanks!  To the British Army it made perfect sense as it was the Artillery which was to destroy or neutralise enemy strong points, not the Armoured Corps.  This doctrine was developed on the basis of WWI experience, where Artillery was King.   It wasn't until battle experience in the Desert showed how wrong this was that thoughts turned to heavier weapons.   Initially they tried to mount two weapons in the one turret.  A 2 Pdr to shoot at tanks and a 3 in Howitzer to shoot at infantry.  However, they encountered problems.  In the Churchill they mounted a 3 in How. in the hull and a 2 Pdr in the turret but  on the basis of experience with first M3 Mediums and them M4 Mediums with a 75mm gun which could do both, opted to adopt that calibre.

The American Army decided that their tanks should be able to engage both enemy armour and infantry.  While they could engage tanks their primary role was that of infantry support.  They provided them with, initially a 37mm gun and when they realise that was inadequate a 75mm gun.  The M3 was only intended to be a stop gap.  They realised that mounting the main gun in the hull was silly but felt they needed to field a medium tank quickly while they developed a proper, turret mounted weapon.

The Ordnance Board (who designed and built the tanks) was throughout WWII fighting a battle with the Army over tank armament.  The Army wanted vehicles which would fit their doctrine, the Ordnance Board was pushing for bigger, heavier vehicles and guns.  The Army kept knocking them back.  Witness the problems over getting the M26 Pershing adopted.   It was basically ready in mid-1944 yet it took over six months to convince the Army to take them!

As for small caliber guns being standard, France, Germany and USSR (= main continental powers) designed & fielded tanks with 75mm class gun well prior mid 1940 (Char B1, Pz-IV, BT-5A/7A). That points out that small caliber guns (even the Soviet 45mm) were way underpowered for infantry support.

In two out of the three cases you name, the 75mm "class gun" was mounted on a heavy tank.  Only the Soviets were trying to mount it on a smaller vehicle.  Its also interesting to note that in all three, the role was that of effectively an "artillery tank" - designed to engage targets with HE, not AP (although AP was provided).  In all three, the main, medium tank gun remained the 37-45mm gun.  Thinking on that didn't change until experience showed the need for a larger calibre.

[dy031101]

One could suggest that the M3 was equally so, but that was also part of US armoured doctrine of the time that was essentially still fighting WWI.

One thing the M3 got going for it over their French counterparts though is mobility.  Fall of France did cause the US to re-tune their armoured forces from trench environment to counter-Blitzkrieg; the M3 is a product of that change, and while it wasn't in theory required to be able to fight anything better than Panzer IV, it was required to be able to outmaneuver those heavies.