M10 Tank Destroyer and M4 Sherman

This might be considered a hypothetical question, but I'll post this anyway. The M10 was a tank destroyer on a Sherman Chassis, but the armor was lighter all the way around with a different shape (sloped) on the sides, which were sloped all the way around including the rear, and also featured a heavier gun. Why didn't US strategists take the Sherman, which the M10 was based from, and modify it to have the same Sherman thickness (2 in.) all the way around with sloped sides and rear like the M10, also including the heavier gun? It seems the sloped aspect of the M10 armor design plus the thickness of the Sherman design and heavier M10 gun would have been an effective combination, and made it more formidable against the bigger German tanks later in the war. The heavier gun would have also fared much better. I guess the question is, why didn't the US strategists see the results of the M10 and use its postive aspects and apply them to the Sherman (sloped all the way around and heavier gun) instead of having separate tank destroyers with thinner armor? Do you think it would have had better results with these modifications? It would seem the manufacturing of just one type of tank at once would result in more of them made quicker. I know US doctrine stated tanks were not meant for tank-to-tank combat and TDs were specifically made to take on tanks, but you'd think after seeing the overwhelming advantage the Germans had before the Pershing was deployed late in the war that the Americans would do something to improve their results and save lives.

 

The short answer is that the armor wasn't the problem. The gun was the problem, and that problem wasn't apparent until D Day.

The MK IV Panzer was the German standard medium tank right up until the end of the war. It had about the same armor as the Sherman. In Africa, both tanks had a similar medium velocity 75 and the British experience was that the Sherman was the superior tank. The Sherman had a faster traverse and in most cases could engage and shoot prior to the MK IV. So, no need was seen to upgrade the armor.

In 1943, the Germans began upgrading the gun on the MK IV and by the invasion in 1944, they could engage at ranges where the Sherman gun was ineffective. And now, of course, the Panther was coming online in large numbers which had not been foreseen by allied intelligence. It was a little late in the day to redesign the Sherman.

 

Get an M10 stick a 17 Pdr in it..
http://en.wikipedia.org/wiki/17pdr_SP_Achilles

Get a Sherman stick a 17 Pdr in it.
http://en.wikipedia.org/wiki/Sherman_Firefly

Get a Sherman stick more armour on it .
It's called a Sherman Jumbo.

Get an M10 , stick a new turret on it with a 90mm gun .
http://en.wikipedia.org/wiki/M36_tank_destroyer

 

The thing is, M10 & TDs in general (though I prefer the term Self-Propelled Anti Tank Gun), are all about the gun, or speed.
Making a 'lightened' tank, is fairly straightforward.
Reversing the process to make a heavier SPATG, is less straightforward.

The M7 & 17pdr guns fitted in M10/Achilles are beastly old things.
75mm weighs M2: 783lb, M3:910lb
17pdr weighs 1885-2032lb
M7 3" weighs 1990lbs

That's quite some extra lump.
So you've already got an extra half ton of ordnance, not counting the heavier and larger mount required.

Add to that, that sharply sloped armour like the M10 carried, which despite being a tad thinner, takes up considerably more surface area.
Beef the armour up to 'tank' thicknesses, and you have a greatly increased total weight of metal being carried on a given chassis.
then stick another slab of steel on for a roof.
(M10 armour was (probably) given a sharper slope to try and improve protection with thinner metal, & to lower profile somewhat; it doesn't automatically follow that the concept can then be improved in reverse.)

More metal=more weight + more strain on the drivetrain + higher fuel consumption + potentially greatly reduced traverse times (unless you fit considerably beefed-up electrics/hydraulics... which bring considerably more weight, again).

The M3/M4 chassis could only take so much.
Firefly was pushing it (have a look inside a Firefly turret; sideways gun fitted by wizards, and not a lot of space).
Jumbo was really pushing it - a lumbering old thing with a fairly specific purpose, far from suited to standard Tank duties (And a considerably more complex redesign of the entire vehicle than it's often given credit for - Jumbo-specific thread here: WW2F: The Jumbo Sherman- Why weren't all US tanks outfitted like this?)
Israeli M50/51 was also really pushing it in many cases. They ditched rather sharply when the supply of indigenous & import designs became more stable.

Add to the above the vast complexities of balancing re-designs & re-manufacturing of current models, combined with priorities of design/production given to new stuff coming through the pipeline (and associated support/logistics gear/doctrines/training), and the fairly simple M10 makes sense, while a 'heavy M10' brings with it a slew of potential difficulties and complexities.

 

Sorry its me , and I don't count rivets I prefer software to hardware.

The M10 TD was also used by the Royal Artillery, who replaced the 76mm gun with the far superior 17pdr as fast as they could. During the Normandy campaign there was a review of the performance of the M10 - which was a popular piece of kit. Several gunners were awarded gallantry medals for using M10s to support infantry attacks in the absence of allied armour.

The Anti Tank regiments wanted better armour , including an armoured roof, the ability to fire the (pintle mounted) MG from under armour. These changes could have been easily implemented by replacing the M10 - with the Sherman Firefly!!.

Instead, the Gunners replaced the US M10 / Achillies by the Archer SP, which had more in common with the German Marder than the M10. This apparently retrograde step, and in the opposite direction to that which the users had requested. This was probably a deliberate step to make it harder for the RA Anti Tank units from over stepping the boundaries of their role and into that of the armour.

Post WW2 the TD concept was dropped and fulfilled by MBT in almost every army..

 

As for US tank destroyers, I prefer the term "M-10 Motor Gun Carriage" to "SPATG". SPATG seems like a military abbreviation for c-ration spaghetti at a glance.

There was no point in continually up-grading and up-gunning the Sherman. We just made more of them. They weren't designed for all that extra added weight.

I think that too much effort was wasted in the tank destroyer program anyway. The US had a tank destroyer battalion for every division in service, including armored divisions. And every infantry division had it's own attached tank battalion as well. When the Tigers and Panthers were first encountered in North Africa, development in a heavy tank should have commenced immediately, or stepped up if already in motion.

 

The problem was that most of those tank destroyer battalions were made up of towed 3 inch guns that could only be used in a defensive role. Even in defense any mobile AT gun like the M10 was worth a half dozen 3 inch guns. Enemy infantry or mortars could knock out a fixed gun before it could get a single shot off. Imagine trying to withdraw or change positions with a truck and a large gun while under fire.

 

Yes I imagine that it would be like a chinese fire drill limbering up the gun and relocating under fire. But still, the US TD doctrine was a waste of assets and effort. From what I've read on it recently, M-10s, M-18s and 36s fired much more HE rounds as opposed to AT rounds, indicating their use was largely employed as infantry support and mobile artillery than in their intended TD roles.

 

Love that truck. Thought at first it was a Mack NO but the grill seems wrong. Maybe a Corbitt 6 ton or maybe even a White? Anyone know? I don't.

 

Obviously 'Gun Motor Carriage' is a nicer term, for almost anything.

The only reason I picked up that SPATG thing (I think from Buckley... not sure), is that it underlines the concept of these machines much better to me than the slightly dramatic 'TANK DESTROYER'.
TD, as a term, fits the not-quite-typical US doctrine, whereas SPATG is clearer - they were AT guns that happened to be more mobile than those on trad carriages & trails. Sometimes people see them as more than that and sometimes they strayed into other roles, circumstance being what it apparently is in war, but despite looking 'tanky', they were never quite tanks.

(Dave, I think that's a Diamond T - a 968? )

 

That grill up front certainly resembles that of a Studebaker.

 

Well it sure beats walking, regardless how it rode.

 

Kodiak,

I agree that the Western allies discovered that an SP was more use than a towed equipment. However, defence wasn't the problem.

In positional defence, towed equipment well emplaced and sited could do as much damage as an SP. The defensive battles of Alam Halfa and Medininne stopped Rommel in North Africa, The Red army's anto tank brigades eroder German armour at Kursk and US anti tank gunners held their own at Mortain and within the Ardennes.

The problem was in the words "Positional" and "well emplaced". A towed equipment might knock out a tank or two but could not move under fire. It took around 12 hours to emplace a British 17 Pdr towed gun. With the time to prepare a position anti tanks guns were fine, and guns were cheaper than tanks so losing a gun for each tank KO was a fair trade. However, between 1943-45 the problem facing the British and US armies was to protect infantry who had just occupied a position from a counter attack supported by armour. A SP Atk gun was invaluable in that role.

 

That's it!

I forgot about the 980's 'baby' brother.

 

I'm afraid that little more armour would not have made a difference. A sloped 2" glacis plate was 'state-of-the-art' in 1942 when 37mm and 50mm guns were the standard tank and AT-guns.

A 75mm medium velocity gun like the M4's had no problems penetrating 2"@45°. To defeat the German 75mm high velocity guns, a tank would need at least 3". That's roughly the kind of armour a 40ton Panther had. And even with 3" you are still vulnerable to Panzerfausts, that were major tank killers in 1944.

 

The OR teams analysing tank hulks in Normandy recommended up gunning the Sherman rather than adding armour.

 

I can't speak for Kursk, but at Mortain only a few guns held on and did a lot of damage. Most of the guns were destroyed before getting a shot at enemy armor. The guns were destroyed by infantry (panzergrenadiers) in most cases before the panzers were even exposed. The problem, I think, is simple terrain. Not every strategic spot has a good natural defilade to cover or conceal a gun, yet a spot like a crossroads must be covered by an AT gun, and the attacker knows that as well as the defenders.

Knowing an AT gun will be there, a screen of infantry is sent in ahead of the panzers until the gun is either spotted or exposes itself with an HE round in support of his own infantry, and at that point the location comes under rifle and machine gun fire, or often mortar fire, and is knocked out. This was the case in the southern approach to the city of Mortain. Several guns were set up in that area where a network of roads come together, but because of the flat terrain cut by hedgerows, they were easily enfiladed by infantry before the panzers were exposed on the roads.

At other locations, somewhat protected from infantry (bridges for example), the towed M5 guns did tremendous damage and stopped the attack in its tracks.

Yet, if SP guns had been available in those southern approaches they could have moved or withdrawn a short distance and perhaps that breach of the line would have never occurred - there was an entire regiment in reserve only a few miles away, but the breach had already occurred before they could intervene, so they could only stop them north of the city.

 

Kodiak,

I am not sure what your sources a re for these statements According to the US Official history, the 823 TD Bn lost 13 wounded, 3 killed, 91 missing, and 11 of its 3-inch guns and prime movers (out of 24 in the two companies engaged and 36 in the Bn) That is C 33 of guns and 20% of their manpower in exchange for C 20 AFVs. Cos A & B were awarded a presidential citation and one platoon commander Lt Springfield a silver star. The unit was at the centre of a successful action to stop the German armour..

You are quite correct that a handful of guns caused most of the casualties, but that seems to be the pattern of C20th warfare. .

It is true that atk guns are vulnerable to infantry. Sure infantry can be sent ahead of the tanks to find anti tank guns, but 1) It ain't Blitzkreig and 2) a well organised defence is likely to have sited some machine guns to take care of infantry.

There was a detailed research report which included the 823's action by Fort Knox called "The employment of four TD Battalions in the ETO" It is on the csgc database at Fort Leavenworth.

At Mortain the 30th Div did not start in prepared positions but had taken over 1st Div positions. It was a foggy morning and as the action developed many TDs were being called forward so this was a meeting engagement rather than a positional defence.. The Germans seem to have led with armour until forced, through casualties to deploy. .

The problem the 823ed experienced was that the infantry and Atk positions were not well tied in. The unit seems to have lost two platoons overrun in this way. Even then the Germans took casualties from the machine guns on the TD vehicles. .

At Abbaye Blanche the road block included a mix of infantry and anti tank guns as Lt Col Lockett commanding the 2nd bn 117th identified the significance of the position and pushed up a platoon and a section of machine guns."the area in front of the position became a graveyard for about 35-40 German tanks and vehicles." .

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