Saturday, 26 May 2018

Pershing With A Long Hand

The opinion that America could win the war with tanks it already had in production was common at the start of 1944. This attitude backfired in the summer of 1944, when it turned out that even the M4A1(76)W with the 76 mm M1 gun was only a partial solution to fighting German tanks. American tanks were taking heavy losses from German Panthers on the battlefield. Another big surprise was the appearance of a new German tank in July of 1944, the Pz.Kpfw. Tiger Ausf. B, also known as the Tiger II. It turned out that no American tank gun was capable of penetrating it from the front. A search for a worthy opponent for these armoured monsters resulted in the creation of the T26E4 Super Pershing and some other variants of the Pershing with long-barreled cannons.

Tank destroyer, American style

The German Tiger II that was rammed by Lieutenant Gorman's crew near Caen was a nasty surprise for the Americans. It was not known how many tanks of this type the Germans had, but it was clear that American tanks and tank destroyers didn't have any reliable weapon against the Tiger II. Even the Heavy Tank T26 and the Gun Motor Carriage T71 (standardized as the Gun Motor Carriage M36 in July of 1944) were not enough. Their 90 mm M3 gun was close to the ballistics of the German 8.8 cm Flak 18 and was not capable of penetrating the front of this tank.

90 mm T15 gun, a concept inspired by the Germans. The requirements make it clear that this is the American analogue of the Pak 43/KwK 43.

The American answer to this new threat did not take long. General Electric proposed a modernization to their Heavy Tank T1E1 (although these tanks were never standardized, they were referred to as M6E2 in the letters). The proposal was to install a 105 mm T5E1 gun into a modified Heavy Tank T26 turret. A draft of such a modernization existed earlier. A plan to install a turret from a T26 tank (which was considered medium at the time) onto a Heavy Tank T1 was made in January of 1944. The project was worked on in the early spring of 1944, but the work was cancelled on March 7th. Nevertheless, this was the starting point for the creation of the Heavy Tank M6A2E1.

Initially, it was proposed that 15 tanks of this type would be built. On August 18th this tank was cancelled, since the M6A2E1 turned out to be too heavy and clumsy. Nevertheless, the project became a sort of mobile laboratory for the development of the gun and turret for another project, the Heavy Tank T29. The American Ordnance Department wanted a larger Heavy Tank T26.

This tank and the Heavy Tank T30 that appeared later (the difference was in its gun, the 155 mm T7) had another issue. It would take time to build and design them. It's not surprising that Ordnance decided to start a third project. This was a specialized tank destroyer built out of the Heavy Tank T26.

A T26E1 tank converted to use the 90 mm T15E1 gun, Aberdeen Proving Grounds, 1945.

One advantage was that the Heavy Tank T26 chassis existed in metal. However, it was not possible to install a 105 mm gun in this turret. Another route was chosen. The Watervliet Arsenal in New York received an order to build a longer version of the 90 mm T14 tank gun. The new gun received the index T15. In addition to the barrel, which was lengthened to 74 calibers, the gun received a bigger shell casing. This allowed increased the muzzle velocity of the T33 armour piercing shell to 975 m/s and the T30E16 subcaliber shot to 1143 m/s. The result was an analogue of the German 8.8 cm KwK 43 L/71. After trials of the T15 on a towed carriage, the Watervliet Arsenal received an order for the construction of two prototypes of an improved version, indexed T15E1.

The gun received a counterweight and a spring balancing mechanism to deal with the added weight.

The T15E1 gun showed excellent results. The front armour of a Panther tank was penetrated at 2377 meters. This was about the same as the effectiveness of the Soviet D-25T 122 mm tank gun and significantly better than the 100 mm D-10T.

However, there were issues after the gun was installed. The first Heavy Tank T26E1 prototype, which was at the Aberdeen Proving Grounds, was chosen for trials. The gun was installed in January of 1945, and it took some effort. The longer barrel resulted in a significant shift to the center of mass. To compensate, a large counterweight was added to the back of the turret. The gun mount was not design for such a long and heavy barrel, so a balancing mechanism was added to the top. The tank, converted by the Wellman Engineering Company, entered trials on January 12th, 1945.

The same tank in late March of 1945. The sides were not yet added to the gun mantlet.

These measures balanced the turret and somewhat increased the mass of the tank. Trials showed another problem. As mentioned above, the new gun had a longer shell casing. As a result, loading the tank became a chore. Fitting the 127 cm long shells into racks was also an issue.

The problem was resolved by loading the propellant separately. The converted gun was indexed T15E2. This gun was installed on a second prototype.

The same tank from the front. Additional armour improved protection, but drastically reduced mobility.

Trials held on March 1st, 1945, led to the Ordnance Committee to approve the tank for service under the index Heavy Tank T26E4 (OCM 26831). With all the changes, the mass of the tank increased to 42.9 tons. To compare, the mass of the T26E3 was 41.5 tons. The length of the tank increased from 8509 to 10312 mm.

A decision was made to send the T26E4 straight to the front lines after the limited standardization. There was not a lot of time to test the new tank, since it was clear that the war would end in a few months. The tank ended up in Europe by March 15th. It was sent to the 3rd Armored Division, which received the Heavy Tank T26E3 shortly prior.

Design of the spaced armour in the front of the hull.

The new tank was accompanied by Captain Elmer Gray from the Tank-Automotive Center. His new ward cost the captain a few gray hairs even before it entered battle. The tank arrived at the division with a few parts missing. The M71E4 telescopic sight was lost on the way, and thus an M71C sight from the T26E3 was taken. After some investigation, it turned out the sight was never lost, it was not there at all, and the tank was sent with an M71C sight. A firing table had to be hurriedly computed.

Another issue was that the ammunition for this tank was mistakenly sent to the 635th battalion with the experimental T8 gun. This was unfortunate, as the T8 used regular rounds used by the 90 mm M1 AA gun and M3 tank gun. The anti-tank gunners had no need for this ammunition, and it took time and effort to return it.

The gun mantlet after improvements.

While all of this was being ironed out, the experimental T26E4 ended up in the hands of the 3rd Maintenance Battalion. Further events are known thanks to the memoirs of Belton Cooper, who served in this unit. A separate chapter is dedicated to the path of the experimental tank. Cooper is credited with the creation of the name "Super Pershing". Cooper's description of the metamorphosis the tank undertook in March of 1945 is interesting.

[The original article had an excerpt from Death Traps here, which will not be reproduced for copyright reasons]

However, Cooper neglected to mention that he did not design the spaced armour. L.R. Price from the Aberdeen Proving Grounds, who was also responsible for the gun mount, directed the work. The result of Price's influence was that the applique armour was a little different from the type usually used by the 3rd Armored Division. The division did use doubled up applique armour, but this type of spaced armour was not used. The influence of a proving grounds specialist can also be seen in the counterweights installed on the gun mantlet.

The back of the turret.

The addition of the applique armour had a noticeable effect on the tank's characteristics. In addition to sagging torsion bars and a significant drop in speed the engine began to overheat. This is not surprising, as the tank's mass grew to 50 tons. The tankers were lucky that the road wheels did not start breaking up at such a weight. The load on the aiming mechanisms increased, and the issue with large rounds did not disappear. However, the tank had one advantage: firepower. A shot fired from 2400 meters during trials penetrated the 80 mm thick front plate of a Panzer IV/70, passed through the whole fighting compartment, punched through the rear armour, and buried itself in the ground.

The finale of the Super Pershing's fighting career. 3rd Armored Division tank park, summer of 1945.

The debut of the T26E4 happened in April of 1945. Cooper witnessed this event.

[The original article had an excerpt from Death Traps here, which will not be reproduced for copyright reasons]

A battle between a Tiger II and the T26E4 is sometimes mentioned, but there is no official confirmation of this fact. The real combat career of the Super Pershing matches Cooper's description. The applique armour was a mistake. Work to protect the tank took up extra time, which, from the looks of it, is what separated the American tank destroyer from its enemies.

Limited standard, limited use

While the first T26E4 was busy on the front lines, work on the second continued. It was built with the discovered drawbacks in mind. For one, it used the altered T15E2 gun with separate propellant. Second, the tank received a new and improved balancing mechanism. The springs were covered up. The chassis of the tank was also newer. A production Heavy Tank T26E3 (serial number 97, registration number 30119907) was used.

The second T26E4 pilot at the Aberdeen Proving Grounds, summer of 1945.

The conversion of the second T26E4, also counted as the first production tank, was completed by Wellman Engineering Company in June of 1945. By that point, the war in Europe was over, and the need for a tank destroyer has passed. Plans drafted in February of 1945 called for 1000 of these vehicles. They would fight alongside T26E3 tanks and perform the same role as the British Sherman Vc. Since the war was over, the order was reduced to 25 in the summer of 1945. The order was not fully cancelled since the Heavy Tank T29/T30 program was slipping, and the T26E4 had the most promising armament of all American tanks at the moment.

The altered balancing mechanism is visible from above.

The tank that arrived at the Aberdeen Proving Grounds in July of 1945 had not only a new gun, but a new balancing mechanism. The tank finally received an M71E4 sight. The hydraulic traverse mechanism was also changed to compensate for the heavier turret. The ammunition rack was also altered. The tank could now hold 54 rounds.

The same tank from the rear.

Trials performed in the summer of 1945 showed that the changes made to the design had a positive impact on crew performance. Nevertheless, some issues remained. Even moving to separate propellant did not spare the crew of troubles. The casing was still too long to work with. In addition, even the new balancing mechanism was not good enough. This protrusion could easily be damaged in battle. The testers' desires were collected and added to a report. Wellman Engineering Company got to work. As a result, the production T26E4 looked somewhat different than the second pilot.

Production T26E4, Aberdeen Proving Grounds, January 1946.

Another T26E4, this time a production sample, arrived at the Aberdeen Proving Grounds in January of 1946. This tank was also not new, it was converted from T26E3 serial number 83, registration number 30119394. This time, the tank looked more like an ordinary T26E3, since the balancing mechanism was changed again. The hydropneumatic system was installed inside the turret. The counterweight was also changed. Its mass increased to 1334 kg. The tank went into production in this state.

The new counterweight.

The final mass of the tank destroyer grew even higher, reaching 44.07 tons. The length of the tank changed after the alterations, to 10465 mm. Theoretically, the maximum gun elevation would be the same as on the T26E3, but it turned out to be a little less during trials: 18.25 degrees instead of 20. This change was deemed acceptable.

This tank was later trialled at Fort Knox.

Army trials at Fort Knox followed these tests. T26E4, registration number 30128151, serial number 1405, was sent to perform them. The objective of the test was to determine the vehicle's characteristics, crew comfort, and the tank's behaviour in conditions as close as possible to combat. On May 9th, 1946, while trials were still ongoing, the Heavy Tank M26 was reclassified as a medium tank.

The altered counteweight is clearly visible.

The aiming mechanisms of the altered T26E4 remained the same as on the M26. The increased weight of the turret had an effect, especially on horizontal aiming. The turret could rotate at a speed of 2.6 RPM instead of the usual 3.3. This had an impact on mobility of fire. The increased load on manual aiming was also problematic. The hydropneumatic balancing mechanism was different than the one used on the M26, which made it harder to service in the field.

Stowage containers with the lids open.

The T15E2 gun, or rather its ammunition, was also heavily criticized. The separate propellant required new ammunition racks, which made the radio harder to access. The opinion regarding convenience was the same as at the Aberdeen Proving Grounds. The long casing was a noticeable drawback. The separate propellant reduced the rate of fire as is, and this additional difficulty soured the impression even further. In addition, damage to the barrel and muzzle brake was noted during firing of AP shells. The commission considered the poor design of the shell as the cause.

A demonstration of how difficult it was to load the gun, even with separate propellant.

The impressions during mobility trials were also mixed. The barrel overhang reduced the tank's ability to cross obstacles. Vertical obstacles were especially serious, as it there was a serious risk to hit the ground and damage the gun. The aiming mechanism was considered insufficiently robust, and changes had to be made. Service time after 800 km of travel also increased.

The tank's gun often clipped the ground while crossing obstacles.

Specialists at Fort Knox concluded that the tank had a whole gamut of drawbacks. The rate of fire, mobility of fire, and obstacle crossing abilities were reduced compared to the M26. The verdict was largely the same as the one that the T26E4 earned on the battlefield. It's not surprising that the tank did not remain in service for long.

The situation with the gun in travel position was not much better.

Only one T26E4 survives to this day. It can be seen at Cantigny Park, Wheaton, Illinois. The other tanks ended their life as shooting range targets. However, the history of long-barreled M26 tanks does not end here. While the first T26E4 was still undergoing trials, work on its replacement was already underway.

Third time's the charm

Moving to separate propellant was a half-measure. The fact that it only partially solved the issue while adding a whole load of problems was clear. It's not surprising that work on a new tank gun began in June of 1945 in parallel with work on the T26E4. The gun was indexed T54, and Watervliet was charged with its development.

90 mm T54 tank gun, designed for the M26E1 tank.

Externally, the T54 gun was very similar to the T15E2. The biggest difference was the use of a single-chamber muzzle brake. This is not surprising, as the objective was to build a gun with identical characteristics to the T15E2. The breech and ammunition were altered more seriously. The issue of a long casing was solved the easy way. Instead of increasing its length, its diameter was increased. In his time, Gladeon Barnes did the same thing then designing a 37 mm shell casing for the M3 gun. Of course, there is no such thing as miracles, and a larger casing meant there was room for fewer shells in the racks. The Americans considered this issue less pressing. It was better to have fewer shells, but to keep the rate of fire at an acceptable level and rid the loader of headaches.

Comparing the sizes of 37, 75, 76, and 90 mm rounds. The furthest round to the right is used in the T54 gun.

A prototype of the T54 gun was ready by February of 1946. Success in trials gave the green light to convert two tanks. Martens Ferry Division, a subsidiary of the Blaw-Knox Company, was given the task. The vehicle, indexed M26E1, was based on the T26E4, among others. The turret was similar to the T26E4, but there were many changes in addition to the new gun. The recoil mechanism was changed, the .30 cal Browning M1919 was replaced with a more powerful .50 cal Browning M2HB. Instead of the M71E4 telescopic sight, the gunner received a different one, the M83C. Since the T54 used different rounds, the racks were redesigned. Instead of 70 rounds in the M26, the T54-armed tank had only 41, 5 of which were carried in the turret.

M26E1 tank, Aberdeen Proving Grounds, March 1947.

Two prototypes of the Medium Tank M26E1 were ready in early 1947. The first tank was sent to the Detroit Arsenal, the second to the Aberdeen Proving Grounds. Trials began in February of 1947 and showed significantly improved characteristics. The shorter casing made the round easier to load. The gun also showed improved precision. It took three tries, but the Americans received a gun that was precise, had high penetration, and was comfortable to use.

The same tank from the right. The significant overhang is noticeable.

Trials were finished by early 1949. By that point it was clear that the budget cuts after the end of WWII meant there was no chance for this gun to enter mass production. The military only had enough money to produce the M46 Patton, effectively the same M26, but with a new engine and a modernized M3 gun.

View from above, turret in travel position.

There were other reasons why the M26E1 did not enter production. In addition to a smaller ammunition capacity, the M26E1 had a number of issues similar to those discovered with the T26E4 during trials at Fort Knox. The excessively long barrel limited mobility. The installation of a large counterweight and a long gun increased the mass of the tank by several tons. Finally, the pressure on the aiming mechanisms increased. The result was not worth the effort.

The only country that managed to create a successful analogue to the German 8.8 cm KwK 43 L/71 was Great Britain. The 84 mm Ordnance QF 20-pounder turned out to be better than the American and German guns. The gun was shorter (66.7 calibers), and its design was more compact. In addition, the gun was installed on the Centurion tank, which had a large turret ring (1880 mm).

The turret of the M26E1 was very similar to the one used on the T26E4.

There was another reason why American long 90 mm guns were effectively useless. However, it's unlikely that the Americans knew about this at the time. The Soviet Union, America's greatest enemy after the end of WWII, had been designing tanks that were protected from the 8.8 cm KwK 43 since 1943. These included, for example, the T-54 and IS-3. Considering the similar characteristics of the KwK 43 and T15/T54, it's likely that the American guns would have proven ineffective. Thankfully, this theory was never put into practice.

A draft of a Heavy Tank T29 turret on the chassis of a Medium Tank T25E1.

To end off, let us mention a vehicle that the Americans did not build at all. The idea of installing the turret from the Heavy Tank T29 on a Medium Tank T25E1 chassis was worked on in 1948. Theoretically, this was possible, although the turret ring diameter would have to be increased. The advantage of this design was that the turret would not have to be redesigned.

The issue was that the turret of the Heavy Tank T29 was significantly heavier than that of the Medium Tank T25E1. Issues with an excessively long barrel did not go away. It's not surprising that the project was cancelled at the draft stage.

8 comments:

  1. Reading this, I was reminded of similar Soviet efforts--say, to mount the D-25T on a KV chassis as a cheap stop-gap for the IS series. Just too many problems to make it worth solving. Trying to up the armor to King Tiger standards just made the problems worse.

    Mounting this gun on a M-26 repeated the same mistake the Germans made with the Panther and the Tiger II--of making essentially tanks that were one-trick ponies, 'heavy' tanks that might excel fighting defensively against armor but which were far less impressive in other roles. People tend to forget that tanks shoot most of their ammo at non-armored targets. If you just wanted to bring the T15E1 to the war on a dedicated heavy tank destroyer platform, to increase US anti-tank capabilities against heavy armor, why wasn't an attempt made to mount this weapon on an M-36 TD instead?

    ReplyDelete
    Replies
    1. The M36 turret wasnt really any larger. In fact the ammo rack being in the bustle would have made loading even more difficult (remember that on the M26 turret the casings were already too long) and complicated things by a lot. Add to that the Sherman chassis underneath needing to carry the weight of the gun, counterweights and also somehow finding ways to stuff ammo in there as well.

      Personally I would have thought a Waffenträger-esque solution being the best idea, of just mounting the gun on a very low hull with a gun shield, which would take us pretty much to a M56 Scorpion.

      Delete
    2. Interestingly enough, some 90-mm ammo destined for the "Super-Pershings" ended up being sent to the 635th TD battalion by mistake, much to their confusion ('why are you sending us these oversized shells that won't fit into our 90-mms')?

      Reading more about the M36, I see they had to redesign the M10's turret to accommodate the 90-mm M3 gun. So I suppose you may be right, if the M-36's redesigned turret was barely adequate for the M3, a further redesign to handle the T15E1 gun probably wasn't doable. I agree with you in concept, but I was searching around where a fit for this gun could be accommodated on an existing weapons system w/o having to redesign a whole new weapon (which likely would not be ready by war's end).

      Delete
    3. You are a 100% correct about these being one trick ponies and only had a tiny chance of coming in contact with a Tiger 2. Nor was it needed. By this time in the war the US had complete air superiority and any Nazi supper tank could be blasted on it's side by a 500 pound bomb. The time and effort would of been better spent giving all American tanks spaced armor for defense against Panzerfaust.

      Delete
    4. Hardly any German tanks were knocked out by aircraft. The USAAF and RAF own BDAs conform this. Aircraft in WW2 did not have accurate enough bombs or powerful enough cannon to knock out very many tanks.

      What they were extremely good at was destroying the logistics train on which the armor depended.

      Delete
    5. I wonder if the US brass weren't just somewhat overreacting in the wake of the only too recent and quite embarassing misjudgement over the Panther? Damn thing turned out to be a LOT more common than projected so it wouldn't be strange if they wanted to avoid repeating the error.

      Plus more practically the Tiger II might have been representative of the next stage in the upward spiral of protection and firepower; even if that specific vehicle should turn out to be too rare to be of consequence (as happened) there was a lengthy list of good reasons to see if their fancy new tank could be "souped up" to deal with those kinds of specs.

      Delete
    6. @Stewart Millen: In regards to coming up with a existing weapon system to carry the 90mm T15E1 gun, personally I think the best option (pre-Pershing) would be a Sherman with a casemate, as odd as it sounds (Think of the T25 AT in WoT). Its the only solution that I could come up with that would give the necessary space to load the ammunition without hammering out an entirely new tank.

      Delete
  2. Fair point. But not having fuel or a busted track the result is the same with the American Army coming down the road. A lot of German solders had doubts about dying for the Third Reich at this point of the war.

    ReplyDelete