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M4A1(T1) L/57: The Very First 76mm Sherman


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  1. 1. Would You Like This Tank?

    • Yes
      20
    • No
      4
    • Maybe / I Don't Know
      1
  2. 2. If Added, What BR Should It Be?

    • 4.0
      4
    • 4.3
      3
    • 4.7
      7
    • 5.0
      5
    • Other (Please Comment)
      0
    • I Don't Know / Don't Mind
      6
  3. 3. If Added, How Should It Be Available To Players?

    • Researchable
      9
    • Premium
      4
    • Event / Tournament
      4
    • Squadron Reward
      3
    • I Don't Know / Don't Mind
      3
    • Other (Please Comment)
      2
  4. 4. If Added, What Should It Be Called?

    • M4A1(T1)
      3
    • M4A1(T1) L/57
      3
    • M4A1(76) L/57
      8
    • M4A1 (L/57)
      1
    • Other (Please Comment)
      2
    • I Don't Know / I Don't Mind
      8


When the USA was first developing a 76mm Sherman, the gun and tank both went through several design changes in order to arrive at a workable design. Before the production 76mm Shermans, which used the turret from the cancelled T23/M27, there was the M4A1(76M1), which used a modified 75mm turret. Just as the 76mm Sherman underwent an evolution from the M4A1(76M1) to its final form, those early M4A1 models were the product of their own series of tests and design changes, leading all the way back to a single M4A1, armed with the original, long-barrelled T1 76mm gun. The final M1 76mm was a 52-calibre gun, but the version first fitted to a Sherman was a full 15 inches longer, and as a 57-calibre gun it had an accordingly higher velocity. This length didn't come without its costs, however, and the gun had to be shortened considerably and the M4A1 heavily modified before handling was considered adequate, the resulting tank being the M4A1(76M1). With only one L/57 M4A1(76) ever built, I'm suggesting this home-grown US Firefly as mainly a Premium or Event vehicle which should offer a new take on the classic Sherman formula. 

 

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History:


From the Sherman's very conception as a design specification, special care had been taken to insist on it being a somewhat modular tank, able to be refitted with a number of different guns while retaining a universal turret design. While in practice only the 105mm gun worked out this way, with the 76mm Sherman opting for a new turret and the 17-Pdr Firefly heavily modifying its own, the possibility of a 76mm gun in the original Sherman turret had been planned for back in the design stage. At that point the intended 76mm gun was the 3-Inch M7, which went on to arm the M10 tank destroyer and M6 heavy tank, but when it came to actually initiating a rearmament program for the Sherman, it was quickly realised that the 3-Inch gun would be too heavy for the tank they'd built, as well as making the turret overly cramped. No Sherman was ever fitted with the M7 gun, even experimentally, as the designers had quickly written it off in favour of making a new weapon using new metallurgical techniques which would allow them to make a lighter, stronger gun. The production M1 weighed 360kg less than the 900kg 3-Inch M7, without any loss in ballistic performance, and by reusing the basic breech design of the 75mm M3 it would also take up a similar amount of room in the turret.

 

Two prototypes of the new 76mm gun, designated T1, were built. They had a barrel length of 57 calibres, or 57 times the 76.2mm diameter of the bore, giving them a length of 4.34m -- as shown by one photo of the tank, in which a line had been painted to indicate the length of the old 75mm, the new gun was almost twice the length of the old. One of these T1 guns was tested as a static mount, but the other was placed into an M4A1 (S/N W-3060572) for testing in the context of a tank turret installation. The results fell well short of the Army's standards, revealing several flaws in the Sherman's design which meant it would never be able to swap to a larger gun the way the designers had hoped: the length of the gun unbalanced the whole turret, putting undue strain on the elevation mechanism and gun mount, as well as the turret ring itself. Because the gun barrel was heavier than the mount was designed for, the elevation gear had to work harder to raise the gun and the gyrostabiliser couldn't handle the forward weight, leaving the tank without any stabilisation whatsoever. The same weight imbalance issue plagued the turret itself: the rear turret bustle had been meant as a counterweight for the original short M3 75mm and M4 105mm, neither of which were as heavy as the T1, nor did they create as much leverage through their length; it simply couldn't balance out the T1's weight, leaving the turret front-heavy and putting unacceptable pressure on the turret ring. Rather than slide smoothly around, the front of the turret would grind against the turret ring, slowing traverse and reducing the angle of slope the tank could safely rotate its turret. 

 

With these less-than-encouraging results came the realisation that the process of rearming the Sherman would be more difficult than expected, sending the designers back to the drawing board to develop a series of alterations which would solve these problems. They created a new, heavier turret bustle and weighted the breech block, countering the gun's weight in both the turret and the gun mount, and since this was still not enough, they also cut 15 inches (38cm) off the end of the gun, reducing it to the 52 calibre (3.96m) length used on all production guns. The new model, designated M4A1(76M1), was much more promising and at one point was recommended for production in enough numbers to equip a company, presumably for field trials. While further redesigns to the 76mm Sherman would see even those improved prototypes left at the wayside, their construction marked the end of the L/57 gun, and for higher-velocity 76mm guns on the Sherman in general, since aside from muzzle breaks the same M1 design would be the weapon of choice for all US Shermans from then on. Abandoned at the very first stage of testing (with good reason), the T1 L/57 is still a fascinating weapon, showing that at one point the Sherman's new gun had the capacity to rival the British 17-Pounder for velocity and tank-killing prowess. Though naturally the US focus on tanks as infantry support meant that the gun was cut down to a more manageable size, rather than extra time and effort being spent making the tank fit the gun the way Britain later did with the 17-Pdr, it's an interesting 'what-if?' scenario to think about. Likewise, though the Sherman's difficulties with the 76mm T1 showed that it could never have handled the heavier 3-Inch M7, it does imply that the M10 could have been rearmed with an L/57 version of the Sherman's M1A1 and handled it just fine -- and, since the M10's anti-armour ability fell off towards the end of the war, might have allowed it to stay at the forefront of the US TD force, rather than be eclipsed by the M18 and M36. We'll never know, but the possibilities make this M4A1 a fascinating vehicle, not to mention its spot in history as the very first Sherman to wield a 76mm gun. 

 

Estimated Penetration Table:

 

m4a1t1.png.a307a2131d05644d69896d882fe34

 

The T1 L/57 gun has the same bore size (76.2mm) as the British 17-Pounder gun, but a proportionally longer barrel: the T1's 4.34m barrel makes it an L/57 gun, whereas the 4.19m 17-Pounder is an L/55, and the 3.96m production 76mm M1 is an L/52. Accounting for differences in ammunition and gun design, I'd expect the T1 L/57 to have similar velocity to its British counterpart -- while T1 is the longer gun, the 17-Pounder's anti-tank capabilities are legendary and its ammunition was specialised for the task, which I'd expect to even things out somewhat. Using the data we have on the US 76mm shells and a velocity of 885 m/s (rounded up from the 17-Pounder's 884 m/s), I've used War Thunder's own AP calculator to get a ball-park estimate for the T1's performance. As this is an early 76mm gun, I've only given it the ammunition that would have been available (i.e. the same ammo issued to the M4A1(76)W), so my table lacks late-war rounds like the M4A3(76)W HVSS's M93 HVAP. Note that the M10's 3-Inch M7 has exactly the same performance as the M1 76mm with these shells.

 

t1.thumb.png.8e60829692ee16a4509b6e0be31

 

These figures are a little worse than the 17-Pounder (no doubt down to differences in ammo design) but nevertheless a major improvement over the standard M1 76mm, with about 30mm more penetration with APCBC and ~25mm more with AP. This is a respectable amount of penetration, capable of dealing with most things frontally except King Tigers, which this tank shouldn't be facing. In a previous version of this post, I implied that lower AP and muzzle velocity than the 17-Pounder seemed unlikely, but I had forgotten about the British gun's considerably more powerful propellant. Best case scenario is that the two would have roughly the same velocity, since the T1 has a longer barrel and lighter rounds, whereas the 17-Pounder has the greater raw power, making my estimates above around the best it's likely to get, rather than the AP with 916 m/s velocity I was suggesting before. It's also entirely possible that even with the longer barrel and lighter shells, the T1 would be the lower velocity gun thanks to the disparity in propellant charges, so to replace my wildly optimistic second estimates I've calculated the AP it would get if its velocity was exactly halfway between the M1 76mm and the 17-Pounder (837.5 m/s) as a kind of worst-case-scenario estimate.

 

t1111.thumb.png.faac6c45ff5862855fbd3161

 

 

 

Specifications:

 

m4a1t111.png.624df3c12740d668c323a6742a2


Length: 6.27m
Width: 2.62m
Height: 2.74m
Weight: >30.6 tons (I'm unsure how much extra weight the gun adds)
Crew: 5 (Commander, Gunner, Loader, Driver, Hull Gunner)
Hull Armour: 19.5-50.8mm front, 38.1mm sides and rear
Turret Armour: 50.8-76.2mm front, 50.8mm sides and rear
Main Armament: 1x 76mm T1 L/57 cannon (71 rounds)
Armament Traversal: -12.5 to 25 degrees elevation, 360 degrees turret traverse (<24 deg/sec)
Secondary Armament: 1x 7.62mm Browning M1919 MG (hull-mounted)
Engine: Continental R975-C4 (400hp at 2400 rpm)
Max Speed: 23.75 mph (38 kph)

 

Its Place In War Thunder:

 

m4a1t11.png.bb71765765f0cc7c1012e47d9c20


In practice, the M4A1 (T1) L/57 is a standard 75mm M4A1 with no AA machine gun, more weight, slower elevation and traverse, no stabiliser -- and an even longer gun than the 17-Pounder, which has a 55-calibre, 4.19m barrel. It trades a bit of almost everything for a lot more punch than the 75mm and 76mm Shermans, firing the same 76mm ammunition at velocities somewhere in the realm of the 17-Pounder's 884 m/s. Depending on the actual velocity of the gun, the possibility is very real that it could penetrate the front of a King Tiger's turret, giving it equal power to the Firefly. Because this is a 75mm M4A1 converted into a 76mm tank, the hull is much weaker and retains the same weak spots that even 20mm-armed Tier Is can take advantage of, along with the awful engine and low top speed. Thanks to the conversion, the tank also has slower elevation and traverse speeds than the M4A1, so I can't imagine this being played as a normal medium tank. Instead, it would be the tank destroyer counterpart to normal Shermans, brought onto the field because its firepower is needed, rather than as a go-everywhere-do-anything 76mm Sherman. Tiger Is and Panthers will be no trouble to penetrate, nor will IS and KV tanks, but the same is true for the M4A1(T1) in return -- it has the armour of a 3.3, and the mobility too, so it's unlikely to be able to make a nuisance of itself the way the speedy M18 and so-weak-it's-tough VFW do. Obviously not a tank that would fit into the main tech tree, it does present a good option for a new Premium, Event reward, or even a Squadron Vehicle. The Sherman as a vehicle is pretty balanced in terms of armour, firepower and mobility, but if you ever wondered what it would have been like if firepower had been the focus at the expense of the other two, this is the tank for you.

 

I hope you like this tank, and I look forward to hearing your thoughts in the comments!

 

Sources:

Sherman, A History of the American Medium Tank, by R.P. Hunnicutt (scans of pages used in the spoiler below)

Spoiler

 

image.thumb.png.c8db4098171dd3e8266ec4f2

image.thumb.png.c4e5e1ce4ebc34198f04b6d5

image.thumb.png.6c755f0f72be6911a4528309

 

 

M4 (76mm) Sherman Medium Tank 1943-65, by Steven J. Zaloga (found online here; as before, pages used in the spoiler below)

Spoiler

 

image.thumb.png.0ca867036ea70e06081e4275

image.thumb.png.b442d5a3eb6f211de5aafc51

 

http://the.shadock.free.fr/sherman_minutia/manufacturer/m4a1psc/m4a1_psc.html

http://www.tanks-encyclopedia.com/ww2/US/M4_Sherman.php

https://en.wikipedia.org/wiki/M4_Sherman

https://en.wikipedia.org/wiki/76_mm_gun_M1

http://www.theshermantank.com/about/sherman-lee-and-variants-gun-data/3-inch-gun-m7-information-page/ (for information on the M10's gun)

https://en.wikipedia.org/wiki/Ordnance_QF_17-pounder (as above, but for the 17-Pounder)

https://en.wikipedia.org/wiki/Caliber_(artillery) 

Edited by Zombificus
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One major correction reason why 17pdr had its penetration was large propellant charge similar in size to that of US 90mm gun.

 

76mm L57 had on other hand just cut down barrel, chamber (being just new lighter design of 76mm m7)itself it's the same as later 76mm guns with equals the same ammunition.

At best your would had very minor velocoty increase in 76mm L57 compared to standard 76mm..

Edited by arczer25
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2 hours ago, arczer25 said:

One major correction reason why 17pdr had its penetration was large propellant charge similar in size to that of US 90mm gun.

 

76mm L57 had on other hand just cut down barrel, chamber (being just new lighter design of 76mm m7)itself it's the same as later 76mm guns with equals the same ammunition.

At best your would had very minor velocoty increase in 76mm L57 compared to standard 76mm..


I had forgotten about the propellant difference, but I disagree that the L/57 would only have a ‘very minor’ velocity increase compared to the M1. We’re talking nearly 40cm more barrel, which is hardly a small increase. Bear in mind that the 17-Pdr only gets ~90 m/s more velocity than the standard M1, which is 23cm shorter than it, even with a bigger propellant charge. The T1 is 15cm longer than the 17-Pdr, and a full 38cm more than the M1, which has got to have an impact on M/V, and the 17-Pounder also fires heavier shells, which take more force to accelerate. Between the longer barrel and lighter shells of T1, and the larger propellant charge of the 17-Pdr, the final velocities of the two guns should be relatively similar.
 

That said, my second estimates (which I did acknowledge as unscientific at the time, for other reasons) are obviously way out — it’s entirely possible, and I’d argue probable, that the T1 had similar velocity to the 17-Pdr, but given the factor of propellant the idea that it might have had a higher velocity, let alone one >900 m/s, is pretty comical. I’ll edit the suggestion to remove the 916 m/s estimates and any suggestions that T1 might have been higher velocity than the British gun, as well as calculate penetration with a lowball velocity estimate roughly halfway between the M1 and 17-Pdr, which will give a more conservative estimation that may be more to your liking. 

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1 hour ago, Zombificus said:


I had forgotten about the propellant difference, but I disagree that the L/57 would only have a ‘very minor’ velocity increase compared to the M1. We’re talking nearly 40cm more barrel, which is hardly a small increase. Bear in mind that the 17-Pdr only gets ~90 m/s more velocity than the standard M1, which is 23cm shorter than it, even with a bigger propellant charge. The T1 is 15cm longer than the 17-Pdr, and a full 38cm more than the M1, which has got to have an impact on M/V, and the 17-Pounder also fires heavier shells, which take more force to accelerate. Between the longer barrel and lighter shells of T1, and the larger propellant charge of the 17-Pdr, the final velocities of the two guns should be relatively similar.
 

That said, my second estimates (which I did acknowledge as unscientific at the time, for other reasons) are obviously way out — it’s entirely possible, and I’d argue probable, that the T1 had similar velocity to the 17-Pdr, but given the factor of propellant the idea that it might have had a higher velocity, let alone one >900 m/s, is pretty comical. I’ll edit the suggestion to remove the 916 m/s estimates and any suggestions that T1 might have been higher velocity than the British gun, as well as calculate penetration with a lowball velocity estimate roughly halfway between the M1 and 17-Pdr, which will give a more conservative estimation that may be more to your liking. 

Barrel length only affect effectiveness of propellant (you need set length for optimal burn, with can vary depending on propellant grain), it won't add massive amount on its own.

Unless propellant burn rate was chosen poorly and it fails to burn completely when projectile is in barrel.

As I sad 17pdr charge is as big as US 90mm..

fb

3 From left 76mm, next 4 17prd and 3 last 90mm

See how beffy 17pdr are?

 

About barrel length affecting velocity, you know 75mm kwk 40? Single cartridge used with two barrel lengths, one L43 second L48, difference between this two 5 calibers give pretty minor increase in velocity

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