"US development efforts for successor to M4" Topic

"British and American Tanks of World War II"
Chamberlain & Ellis

American medium tank development to replace the Sherman M4 –

Once the M4 series had reached production status, consideration was immediately given to its successor. On May 25, 1942, the Ordnance Department received confirmation from the Supply Service that it could go ahead with designing and procuring a pilot model for an improved medium tank, provisionally designated M4X. Broad requirements called for a 32 (short) ton vehicle with automatic 75mm gun, 4in of front armor and a top speed of 25mph. A wooden mockup was accordingly built by Fisher, one of the medium tank producers. By September 1942 it had been agreed by the Ordnance Department, after consulting the Armored Force Board, to build three plot models of 30 tons maximum weight, each with different armament and interchangeable turrets. The first one, T20, was to have a 76mm gun and HVSS, the second, T20E1, was to have HVSS and a 75mm automatic gun, while the third, T20E2, was to have a 3in gun and torsion bar suspension. Each was to be powered by the new Ford GAN V-8 tank engine and have a torque converter and Hydra-matic transmission. The T20 was built by Fisher and complete in June 1943. The T20E1 was cancelled but its turret was used in the T22E1.

The T20E2 was completed by Fisher as the T20E3 with 76mm instead of 3in gun.

Both the T20 and the T20E3 were tested but the transmission system gave much trouble with oil leaks and overheating. Development of these vehicles ceased at the end of 1944, by which time developments had proceeded to much later types. Experience and information gathered from these vehicles under test was useful, however, for development of later T20 range tanks. Maximum armor thickness of these T20 tanks was 62mm at the front, they a 47 degree sloped hull front, were all welded with a cast turret, and featured several standard fittings from the M4 series. In the T20 series, drive was to the rear.

- – -

The T22 was a development of the T20 series initiated in October 1942. Chrysler were asked to build two pilot tanks identical in all respects to the T20 except for the transmission which was to be of the same five-speed mechanical type as used in the M4 medium tank. Trouble was experienced with the transmission and the rear drive, however, on tests and work on the T22 project was formally cancelled in December 1944. Both vehicles had been completed in June 1943.

Subsequently the first pilot model was converted to take the special turret with 75mm automatic gun which United Shoe Machinery Corp had built for the projected T20E1. In its new guise, the T22 was redesignated T22E1. The turret was virtually a lengthened M4 type, the gun was the standard M3 weapon, and the mount was the standard M34 type. Main feature was the automatic hydraulic loader with two magazines, one for HE and one for AP ammunition, selected remotely as required by the commander who was located in the left rear of the turret. The only other turret occupant was the gunner, and there was no loader. Tests at APG gave a maximum rate of fire of 20 round per minute, but the magazines and loading mechanism were unreliable.

By this time, however, there was a requirement for a heavier calibre gun, and the project was cancelled in December 1944. Apart from the transmission (and the turret in the T22E1) data and characteristics for the T22 series were the same as for the T20. T22E2 was the projected equivalent of the T20E2 with 3in gun. It was cancelled in the design stage.

- – -

Development of the T23 was authorized at the same time as that of the T22 (i.e. – October 1942). Hull, armament and general external layout were similar to the T22, but vertical volute suspension and tracks as used on the M4 series were to be fitted and electric transmission was specified, the drive units being built by General Electric. As with the T22, three pilot models were asked for, the T23 with 76mm gun, the T23E1 with 75mm automatic gun, and the T23E2 with 3in gun. However, as in the T20 series, the projects for vehicles with 75mm gun and 3in gun were cancelled before completion. The T23 pilot model was, in fact, the first of the T20 type tanks to be completed, finished by Detroit Arsenal in January 1943 and under test before either the T20 or the T22. A second pilot model was ready by March 1943. The pilot models were tested at Fort Knox and proved to be very maneuverable. In May 1943 a "limited procurement" order of 250 vehicles was commended, subject to detail improvements. These vehicles were built by Detroit Arsenal between November 1943 and December 1944, differing from the pilot models in having an all-round vision cupola for the commander, a rotating hatch for the loader, an improved gun mount (the T80), and an improved 76mm gun, the M1A1. Though used in limited numbers in America, the T23 was never standardized and never generally issued or used in combat.

Main reason for this was that Army Ground Forces were already quite satisfied with the M4 medium tank while the Armored Force Board considered some T23 features unsatisfactory, in particular poor weight distribution, excessive ground pressure, and a mode of transmission which was untried in the long term and possible suspect. They requested ten T23s for further trials in an attempt to overcome these shortcomings. First of these ordered was designated T23E3 and was to have torsion bar suspension and 19in tracks, while the second, T23E4 was to have HVSS and wide tracks. This later vehicles was subsequently cancelled, however,

The T23E3, completed by Chrysler at Detroit Arsenal in August 1944, had a turret taken from a production T23 and torsion bar suspension taken from the T25E1. All other features were the same as the T23 but the turret basket was eliminated to give increased ammunition stowage and the electric transmission was fully waterproofed, a retrospective modification also featured in late production T23s. On the basis of experience with the T20E3, which by this time had been completed with torsion bar suspension, the Ordnance Department requested in July 1943 that the T23E3 be standardized as the Medium Tank M27 and the T20E3 be standardized as the M27B1 both for immediate production in view of the fact that the M4 medium tanks would be seriously obsolescent by 1944. This was rejected by Army Service Forces and no further progress was made with standardizing the T23 series.

In the event, however, this led to numerous improvements being made in the M4 series for introduction from late 1943 onwards and many of the features tried or developed in the T20-T23 tanks were incorporated into M4 vehicles, in particular the complete T23 type turret and 76mm gun, HVSS, and the simplified 47 degree hull front. Thus, while the T20-T23 series vehicles did not see general service or combat, they played a most important part in US tnk development in the late war period leading to improvements in the M4 design and, as developed into the T25 and T26, leading to the evolution of the M26 heavy tank.

- – -

Concurrently with the design of the T25, designs were drawn up for a more heavily armoured version, designated T26. This would have had electric transmission, as in the T25. Development studies showed that both the T25 and T26 with this transmission would be excessively heavy, the T26 weighing more than 45 (short) tons. In view of this, the T25 was redesigned with Torque-matic transmission (Hydra-matic transmission with a torque converter) and the same changes were, of course, incorporated in the T26 design. Only the T26 pilot model was therefore built and the 10 scheduled production vehicles for test purposes were all completed as T26E1s by Grand Blanc Arsenal in March-June 1944. The T26E1 was similar in most characteristics to the T25E1 but had wider tracks (24in), increased overall width (11ft 2in), a shorter hull (22ft 4.75in), increased armour maximum (100mm) and a corresponding increased weight (86,500lb). Other details were the same as those of the T25E1.

Meanwhile in September 1943, the Ordnance Department had urged immediate production of 500 T25E1s and 500 T26E1s for delivery in 1944, but this was opposed by both the Armored Force Board, who would have preferred the 90mm gun mounted in the M4 medium tank, and by the commander of Army Ground Forces who did not consider a 90mm gun desirable in a tank since it would encourage tank units to stalk enemy tanks, a role assigned to tank destroyers in the then-current armour doctrine of the US Army. Army Ground Forces, instead, requested in April (Blutarski – 1944?) 7,000 T25E1s with 75mm guns and 1,000 T26E1s with a 76mm gun. This clearly impractical request – which would have involved further development work and, in any case, duplicated existing types with smaller calibre guns – was not resolved until June 1944 when all the T26E1 development vehicles had been completed. On June 1st, a statement came from European Theater of Operations that they required no new vehicles with 75mm or 76mm guns in 1945; instead they wanted tanks with 90mm and 105mm (Blutarski – guns or howitzers?) weapons in the ratio 1:4. Their request was upheld by the Army Staff and the T26E1 underwent its trials programme as planned. At the end of June 1944 the T26E1 was reclassified Heavy Tank T26E1 and its development history as prototype for the M26 Pershing is accordingly continued in the American heavy tank section of this book.

- – -

In June 1944 as related previously (see T26 medium tank series), the T26E1 was redesignated Heavy Tank T26E1. Extensive trials were carried out with the ten T26E1 pilot models by the Ordnance Department and numerous detail modifications were made for incorporation in production vehicles. These included improvements to the transmission and the engine cooling, revised electrical system removal of the turret cage to increase ammunition stowage, better engine access, and larger air cleaners. In August 1944, the Ordnance recommended that the T26E1 be standardized and placed into production. Opposition from the user arms was still strong, however, and Army Ground Forces still disagreed and stated that the vehicle could not be standardized until the Armored Force Board had also tested and approved the production modifications. Earlier, in July, Army Ground Forces had tried another delaying move by requesting that the T26E1 be redesigned with the 76mm gun, a retrograde idea ignored by the Ordnance Department. It was not until December 1944 that the T26E1 was approved for "limited procurement" and production vehicles, with the various modifications earlier suggested, were designated T26E3 to distinguish them from the pilot models.

Production of the first 20 T26E3s had begun in November and the Ordnance Department proposed early in December that these be shipped straight to Europe for combat testing. Once again Army Ground Forces was opposed to the idea and asked that they first go to the Armored Force for testing and "certification of battleworthiness". This would have wasted yet another month. However, within a week of this exchange, two German panzer armies savagely hammered the US 1st Army in the lightning Ardennes Offensive, Decmber 16, 1944. Among other things, this reverse spotlighted the inadequacies of the M4 medium with its relatively light armour and 76mm gun; undoubtedly this was a factor which caused the American General Staff to intervene in the T26 affair on December 22 (Blutarski – just as they had been earlier forced to do in connection with the T71/M36), and order immediate shipment of T26E3s to Europe without further testing.

The first 20 T26E3s were shipped to Europe in January 1945 and at the beginning of February these were issued for service to the 3rd and 9th Armored Divisions. The Ardennes Offensive had indeed vindicated the Ordnance Department's persistent attempts to get a tank with a 90mm gun into service. In January 1945 Army Ground Forces had no hesitation in agreeing that the T26E3 be considered battleworthy, and the cry for more vehicles came from ETO where tank crews were favorably impressed with the new tank which was nearly a match for the Tiger in a straight shooting match, and very much more mobile. Full production of the T26E3 was ordered in January 1945 and it was built by Grand Blanc Arsenal (November 1944 – June 1945: 1,190) and later Detroit Arsenal (March – June 1945: 246). In March 1945 the T26E3 was standardized as the Heavy Tank M26 and it was named "General Pershing", usually shortened to "Pershing". Later in 1945, the M26 saw action in the Pacific, being used in the taking of Okinawa.

B

The Chieftain on youtube on the same subject: YouTube link

Chris

Hi Chris,
Hope you are keeping well. It has been a long time.

Re Mr Moran – I'm not really a fan. IMO, he tends to be a bit "selective" in his interpretations of the historical record.

B

CAn we have a example of his " Selective" interpretations.

Sure, Wackamole9.

Listen to the Youtube link, then read the above extract from Chamberlain and Ellis, then read further in "Beachhead to Battlefront" history of the US Ordnance Department here – link

B

Listen to the Youtube link, then read the above extract from Chamberlain and Ellis…

I have done so. Seems to me to be rather more expansive vs. more selective than the written extract. But in any case I don't see anything that could cause me to disparage the account offered by the Chieftain.

As to the Ordnance Department account … haven't gone through it, but from what I have heard (2nd hand) from others who have interest in researching the archives for primary correspondence and reports, I might take the Ordnance accounting with a grain of salt. Seems it was, as one might say, "selective in its interpretations, with a bend towards making Ordnance look good.

Not that the Chieftain seems to bend towards making Ordnance look bad. Not at all. But he doesn't have a dog in the fight, other than generally being as interested in the user's (ie: the tanker's) perspective as he is in the historian's, designer's, logistician's, general's, or politician's perspectives.

-Mark
(aka: Mk 1)

Thought this was about the M4 rifle, and not the tank.

WWII should have been the giveaway, but went unnoticed.

Too many weapons systems with the same designation.

IMO, he tends to be a bit "selective" in his interpretations of the historical record.

Well he does have a lot of archival documentation supporting his interpretations.

"British and American Tanks of World War II" is rather dated having been first published in 1969. A lot of new information has been found since then and a fair amount of myths revealed since then.

I think the big difference between the "Official account" and Moran's work is that he used the actual documents, memos and reports from the archives.

Official accounts have a tendency to gloss over some of the lesser moments of certain people and highlight the good ones. Put the official "German accounts of the War" the US commissioned from former chief of staff Franz Halder and what surfaced from the archives that reappeared after the Cold War doesn't quite mesh up.

But the broad lines of the development do match.

- Ordnance didn't sit on its laurels, instead of declaring the M4 to be "perfect" in every way, like every other claim on the Histery Channel, they continued to improve and work out new things.
- They were clearly steaming ahead with the development of new guns, larger tank designs and other features. Yes some were dead-ends, but the broad range offset the mistakes.
- There were clear problems with introducing a new tank design especially a heavy one, correctly voiced by the engineers and logistics.
- The M7 Medium turned out to be a serious debacle, part of why people were not itching to push a new design when existing tanks worked well within expectations and were continuously being improved.
- When everything finally clicked, the M26 was introduced in a matter of months, by which time it was a sufficiently-tested design and work was already under way to fix inherent problems like the underpowered engine and beefing up the transmission, though the work was put on the back burner when the war ended only to resume in 1948.

And the predictions of the Corps of Engineers did turn out to be true. The Pershings at Remagen couldn't cross the bridge. They couldn't even start to ship them until sufficiently strong cranes had been built in US ports and in Antwerp to actually them onto and off ships.

Thought this was about the M4 rifle, and not the tank.

Too many weapons systems with the same designation.

At least it was not about M3, which has many more designations – at least in the WWII context.

a 32 (short) ton vehicle with automatic 75mm gun, 4in of front armor and a top speed of 25mph

That sounds like an incremental and surprisingly unambitious spec. They could have largely achieved it simply by up-armouring the glacis of the M4, surely.

Hi 4th Cuirassier – According to the authors, design development on the T series medium tank projects did translate over to the Sherman in various respects – the adoption of the 47deg glacis angle was one mentioned in particular. If I am reading "the tea leaves" correctly, I suspect that original 100mm glacis thickness fell victim to overall vehicle weight considerations – except, of course, for the field-modified ETO Jumbos whose builders were not obliged to report to bureaucratic overseers.

B

Automatic loader for a 75 mm tank gun sounds a bit ambitious in early 40's, though. To my knowledge, there had not been many automatically fed tank guns by then – the only one that I can think at the moment was the 20 mm gun in Panzer II.

"When everything finally clicked, the M26 was introduced in a matter of months, by which time it was a sufficiently-tested design".

….. Not according to AGF; they were still fighting against deployment as late as December 1944 – when Army General Staff AGAIN was forced to intervene with AGF, break the bureaucratic obstructionism and get immediate delivery of T26E3's to the ETO (Note that the T26E3 was not officially "standardized" as the M26 until March 1945).

Cautions about over-reliance upon "Official History" are absolutely well taken. It is necessary to read broadly, critically and "between the lines" to gain any reasonably accurate picture of what really happens within any complex bureaucracy. I have some modest experience in that arena and my appraisal of the US wartime tank development program is that it was dominated by a three year bureaucratic turf war waged among multiple US Army stateside fiefdoms at the expense of the overseas fighting man.

- – -

"British and American Tanks of World War II" is rather dated having been first published in 1969."

The age of the document is not important; what is important is its accuracy and correctness. In that respect, what Chamberlain and Ellis have presented is consistent with other later scholarship I have consulted.

FWIW.

B

Hi Griefbringer,
I agree with your comment about the auto-loading 75mm project – very ambitious.

I also wonder at the motivation behind it. At 42 rounds per minute maximum rate of fire, a tank could theoretically fire off its entire ammunition load in less than two minutes (not that anyone would ever have occasion to do such a thing). Why so fast. Even with auto-loading, it is desirable to make sure of one's aim. Would not a more modest rate of fire (say one round every 3 to 5 seconds) have been sufficient?

B

I will start reading the books you mentioned. I'am always fascinated by the war within the war within the war. Many of the "bean counters" decisions in the later war in the US had truly horrible consequence for the frontline troops.

Weight is a major issue, it's not something you can handwave away when it comes to wear and tear of the suspension.

Take something that everybody sees as an obvious advantage : broad tracks on tanks. The broader the better, case closed, but adding even a few inches to your tracks quickly brings up the weight and before you know it you put one or two tons of extra strain on the transmission. And repairing and replacing a heavier track means the crew may need a lot more time to do so and will be exhausted.

Same for extra armour, until you reach critical weights where you need extra heavy cranes to load it into ships, you make it harder to move tanks by rail, since not all flatcars can handle that extra weight. Ditto for bridges (regular bridges and engineer built ones)

Even a "Medium" tank of "modest" weight like the M26 could run into problems. US army tried to move a battalion of them by rail in 1947, took them weeks to gather all the required flatcars.

I'm convinced that if they had actually fast-tracked the M26 like so many still claim till now, today we would be talking about the "Wannabe-Panther" M26, which was unreliable, too heavy which forced commanders to send M5 Lights into battle and got them massacred because the engineers were too stupid to build better bridges, and it would be referred to as that piece of underpowered, mechanically unreliable junk that was effortlessly defeated by Panthers and Tigers because the US army was too dumb to fast-track the T29 Super Heavy tank in the first place !!! And then cue some conspiracy theory that the M26 was personally sabotaged by Patton because he couldn't live with the idea of the M26 replacing his beloved, perfect M4 Medium or somesuch, which if they had not introduced the M26 would have certainly lost the war …

I agree with your comment about the auto-loading 75mm project – very ambitious.

I also wonder at the motivation behind it. At 42 rounds per minute maximum rate of fire, a tank could theoretically fire off its entire ammunition load in less than two minutes (not that anyone would ever have occasion to do such a thing). Why so fast. Even with auto-loading, it is desirable to make sure of one's aim. Would not a more modest rate of fire (say one round every 3 to 5 seconds) have been sufficient?

I would assume that for an automatic loader to appear as worthwhile in practice, it would need to be faster and more reliable than a human loader. Also, depending on how it was powered, making it slower might not have been any easier.

Of course removing the loader means that less space is required in the turret for the crew, but on the other hand the loading mechanism would likely take quite some space – and as much ammunition as possible would need to be stored in the turret to take advantage of it.

Naturally there is an associated manpower saving – dropping one crew member per medium tank equals to around 60 men per US armored division. However, that also means fewer crew members to take care of the tank maintenance and other tasks outside combat.

Hi Patrick,
Agree re the consequences of weight. But (IMO) it all becomes a complex balancing act as to whether the benefit derived is worth the penalty paid. Things such as ground pressure and suspension behavior can be quite subjective.

With respect to the logistical implications of heavyweight vehicles: where there is a will, there is a way. The Germans managed to transport 60+ ton Tiger tanks to Tunisia by sea and everywhere in Europe by rail with relatively minor inconvenience (had to change tracks). BTW, I did some investigation into the oceanic transport of the 46 ton T26E3 to the ETO and my belief is that they were most likely conveyed by LSTs. These were oceangoing vessels with ramps, so derrick lift capacity was not an issue. According to my 1949 US Army logistical manual, an LST could carry ten M26s.

Interesting side-note re the T26/M26 -
The T26 started as a Medium Tank development project, but the T26E3/M26 was later re-classified as a Heavy Tank. Given that the T26 program was actually defined as an up-armored version of the T25, this makes some sort of bureaucratic sense.

Re your closing remark – I would agree that the M26 could be fairly described as a US analog to the Panther. They in fact shared certain characteristics – similar weight, powerful gun, heavy frontal armor, more sophisticated suspension, delicate mechanicals, pushed to the warfront to meet a need (IMO, AGF's demand to re-test the M26 for "battle-worthiness" after it had already been put through its paces at APG by BuOrd was far more a case of last-ditch bureaucratic obstructionism than anything else).

A last remark on the subject of vehicle weight – The US Army already had a heavy vehicle in its inventory in 1944: the M40 155mm SP gun (40.5 tons) was used in large numbers in the ETO.

FWIW.

B

The Germans relied far more on rail than any other nation with the possible exception of the Soviet Union and had planned accordingly. Given that fuel went to the combat vehicles and the industry first and trucks last, trains powered by plentiful German coal were a great way of solving transport and logistics issues to a degree. The problems usually happened as soon as the tanks had to leave the railhead and move on their own power to the staging areas or even to the battlefield itself. Further problems happened when the planned conversion of the Soviet rail network did not go as planned and German locomotives broke down at an alarming rate under the adverse conditions.

The lack of proper towing vehicles or even transports was a huge disadvantage for the Germans. They never had the equivalent of the Dragon Wagon, often having to use some kind of heavy Famo halftrack and trailer combination or tow broken tanks by using several connected halftracks.

The Tigers of 501st Heavy Battalion were loaded onto trains to Italy and then shipped by ferry via Sicilly, there are photos in Tigers in Combat I showing it was a very tight squeeze. The first three Tigers arriving in November 1942 and by January 1943 they had 13, supplemented by Panzer III and IV. It's only a short distance from Messina to Bizerte. Therefore they didn't require cranes or other equipment. A Tiger captured by the US in North Africa was shipped in 1943 to New York, requiring it to remove the turret and tracks if I recall correctly.

We find that the Germans had prioritized a land-based logistics system and that they didn't have the kind of capacity to move heavy tanks other than short distances over rivers or the relative calm waters of the Mediterranean by ferries that looked quite overburdened by the size and weight of the tanks.

The US used a similar approach, building pontoon ferries to move M26 tanks across the Rhine, partially to avoid the risk of the M26 crashing through pontoon bridges and holding up the advance.

I have a book about the history of the port of Antwerp where it is stated that several high tonnage cranes were installed in Antwerp to help unload tanks and other equipment such as locomotives after the war, one of them still being in service by the 1980's.

If I remember right, with the slope, the M4 had almost the same armor thickness as the vertical slab of armor the Tiger used. Just the German guns of the period would penetrate that amount of armor, as opposed to the 75mm of the US gun.

At least it was not about M3, which has many more designations – at least in the WWII context.

Agreed!

One can only wonder and the confusion when cryptic communications were needed for radio messages in combat zones.

Guy at the sharp end: "We need support at our position."
REMF: "Acknowledged. Sending some M3s."
Guy at sharp end: scratches his head and ponders meaning…
Could be:
-Medium tanks.
-Light tanks.
-Tank destroyers.
-Half-tracks.
-Submachine guns.
-Replacement 75mm guns for Medium tanks.
-Can openers.

Yeah. Maybe not the best method.

-Mark
(aka: Mk 1)

Mark, don't forget M3 scout car, M3 howitzer and M3 carbine…

@ doug

That's true, although as gamers, I wonder if we sometimes miss the value of sheer cubic inches, and maybe overvalue slope.

A glacis 50mm thick sloped at 60 degrees from the vertical presents a thickness of twice that amount to an incoming round, provided a/ the tank is on level ground and b/ that the incoming round is travelling parallel to the ground and coming in head-on. If either of those is not so, then the sloping armour's actual presented thickness falls, whereas that of vertical armour increases.

In the case, for example, of an anti-tank gun firing at a tank as it descends a slope, the slope of the slope (IYSWIM) will act to lessen the slope of its armour. If it has vertical armour, the slope of the slope will increase the thickness presented.

I would posit that rounds fired from the normal against targets on level ground were the exception, not the rule. This supposition is supported by most armies' tendency to estimate AP performance by measuring what depth of plate the round could defeat at a 30-degrees incidence angle.

The Germans, in designing a box-shaped tank in 1941 that was still tactically competitive against slopey-shaped tanks in 1945, may not have been wholly stupid. The Tiger's armour advantage may been that you almost never got to fire upon it at right angles owing to the typical tactical situation, so its nominal four inches may have amounted to five or six.

Once you got to the point where weapons like the 17-pounder were commonplace, it made no difference whether you had four, five or six inches of armour, the round was going to go through just the same. Hence the post-war move to sloped armour. I do suspect, though, that the usual view – the Panther's sloped glacis offered better protection than the Tiger's thicker but upright glacis – may be an oversimplification.

+1 > 4thC.

May I add that obliquity in the horizontal plane was (IMO) probably even more important.

B

Here is a calculator to figure it out:
link

Wolfhag

A last remark on the subject of vehicle weight – The US Army already had a heavy vehicle in its inventory in 1944: the M40 155mm SP gun (40.5 tons) was used in large numbers in the ETO.

Hate to be a stickler for details here, but … I believe that the number of 155mm SP gun M40s sent to ETO was ONE. And that was sent in 1945, not 1944. Most likely (not entirely sure) when it was still type-identified as the T83 prototype, because it was only accepted for service as the M40 in March of 1945, so having M40s in inventory in 1944, even if they were not shipped to ETO, would seem a peculiar event worthy of further explanation.

All in all, not entirely dissimilar from the path of the T26E3 being sent to ETO prior to acceptance as the M26. Except that the T26s were sent in "some numbers" (I would hesitate to say "large numbers") before type acceptance. Whereas, to my understanding, only ONE T83 / M40 was sent to ETO during WW2. More, of course, wound up in Europe AFTER WW2, but that hardly qualifies for our discussion, as it was no longer ETO after the war, and besides we are not discussing post-war vehicles (unless we also want to consider M47 tanks in ETO, etc).

If this was in fact just a mis-identification of vehicle type (hey, can happen to any of us), then the only equivalent type of US Army vehicle I could think of for comparison from the US Army arsenal would be the 155mm GMC M12. These were type accepted in 1942, and saw service in ETO in 1944. But alas, they were only about 27 tons, so not greatly different in weight than an M4 tank (although built on the M3 Medium chassis, as the M4 chassis was not yet available when designing a new SP artillery platform for type-acceptance in time for service in ETO).

Even so I would hesitate to use the term "large numbers", as only something like 100 M12s were ever built, and while I'm not entirely sure, I believe only a portion of the those built (produced in 1942 and 1943) were shipped to ETO. So if we are not comfortable saying Shermans with 76mm guns were available in "large numbers" by July 1944, or HVAP ammunition was available in "large numbers", I would hesitate to say the M12 qualifies as sent in "large numbers".

It's also possible I have the numbers wrong. I have no objection to being corrected where I do. Good and useful numbers always help my understanding of the history of this period, even when they cause me to adjust my pre-conceived notions.

-Mark
(aka: Mk 1)

Hi Mark,
I checked some other references regardingthe M40 and you are spot on: only a very small handful of M40s made it to the ETO before the end of the war.

I was misled by a remark in an old reference book of mine ("Tank Data – Aberdeen Proving Ground Series", volume 1). The summary remark on the M40 entry (p.228) stated –

"This was the U.S. 155-mm "Long Tom" mounted on the tank chassis. It saw service in ETO in great numbers."

- which was obviously incorrect. Perhaps the author(s) meant to refer to the Korean War. Thanks for pointing that out.

B

Postscript – Apparently the Sherman Jumbo, at least according to this website – link
- weighed in at 42 short tons. Interesting.

Not to quibble but Hunnicutt's book has the M4A3E2 at 84,000 combat loaded (so 42 short tons) but unstowed weight, likely used for shipping, was 77,500 so closer to 38.5 short tons. Still a big boy!

It seems that, at some point in 1943/44, AGF must have made its peace with armored vehicles in the 40 ton range – Pershing, Jumbo, M40 and another heavy SP artillery vehicle.

B

+1 > 4thC
Also vertical plate rested in a more efficient use of space on the inside meaning a "smaller" tank. Compare Sherman to the Cromwell.
Once the velocity and impact of shells reached the point that they would no longer be deflected by the slope it comes down to metal quality and mm at point of impact