76 mm Gun M1

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Summary

The 76 mm gun M1 is a high-velocity cannon made to give the US armored forces an extra punch against enemy tanks. Although taking the same projectiless as the 3-inch Gun M7 (but different casings), it was lighter and had a simplified beech. The 76 mm Gun M1 supplemented the 75 mm Gun M3 on the Sherman design as its main armament during latter half of World War II, giving the Allied tank units better firepower against the more heavily armored German tanks that the 75 mm are unable to deal with effectively. It was succeeded as a tank armament by the 90 mm Gun M3.

Variants

  • T1 - Experimental model, 57 caliber long
  • M1 - Standardized T1, Refers to both 57 and 52 caliber version.
  • M1A1 - Gun barrel has some changes to external contour. Recoil surface extended to allow trunnions to be moved forward to balance weapon, also has a breech counterweight installed to compensate the long barrel of the gun. 52 caliber long
  • M1A1C - The M1A1 with a threaded end for muzzle brake attachment to solve the dust issue when firing.
  • M1A2 - Improved barrel and breech, rifling twist now made one turn in 32 calibers compared to previous 40 calibers, all had muzzle brakes.

Game usage

The 76 mm gives the medium tank line-up a very noticeable upgrade in firepower. It gives an average of 100 mm of penetration in standard combat ranges. While still weaker in comparison to other guns like the 17-pounder, the 76 mm enjoys the luxury of an explosive filler in the M62 shell that can cause beyond-armor damages at standard enemy tanks. The gun's worst enemy at this stage is large interior volume as the explosive filler is not that great and great internal space like on a Tiger I could make the resulting shrapnel and explosive force effect only a certain sector of the tank.

Guns of comparable performance

Users

M1

M1A1

M1A2

Ammunition

Historical

Available rounds for the gun:

  • M79 Shot - Standard AP shell
  • M42A1 Shell - Standard HE shell
  • M62 Shell - APCBC round with explosive filler
  • M93 Shot - APCR round
  • M88 Shell - Smoke round
  • M85 Shot - Target practice round

Game Statistics

Ammunition Penetration in mm @ 90° Type of
warhead
Velocity
in m/s
Projectile
Mass in kg
Fuse delay in m: Fuse sensitivity in mm: Explosive Mass in
TNT equivalent
in g:
Normalization At 30° from horizontal: Ricochet:
10m 100m 500m 1000m 1500m 2000m 0% 50% 100%
M62 Shell 127 125 116 106 97 89 APCBC 792 7 1.2 20 63.7 +4° 42° 27° 19°
M42A1 Shell 7 7 7 7 7 7 HE 800 5.8 0.1 0.5 390 11° 10°
M79 Shot 155 154 131 107 88 72 AP 792 6.8 N/A N/A N/A -1° 43° 30° 25°
*M93 Shot 221 215 203 181 154 124 APCR 1036 4.3 N/A N/A N/A +1.5° 24° 20° 18°

* - Not available on the T20, M4A1 (76), M4A2 (76), and the ★M4A2 (76) W Shermans

Ammunition Type of
warhead
Velocity
in m/s
Projectile
Mass in kg
Screen radius
in m
Screen time
in s
Screen hold time
in s:
Explosive Mass in
TNT equivalent
in g:
M88 Smoke 274 3.4 13 5 20 50

History of creation and combat usage

Development

During the inter-war period, the Americans had access to the 3-inch Gun M1918 anti-aircraft gun in their inventory that fired a high-velocity 76.2 mm shell. In September 1940, it was decided to adapt the gun into a anti-tank role. Though the adaption was a success with a towed variant and mounted on the M10 tank destroyer, it was too heavy and cumbersome for a medium tank mount. Sometime in 1942, the development of a new gun to replace the 75 mm on the M4 Sherman's mount began as the 76 mm Gun T1. It should be noted that despite the name, it has the same exact bore as 3-inch (76.2 mm) and is only named such to avoid ammo compatibility error between the 3-inch and the 76 mm. The developed 76 mm used a barrel lighter than the 3-inch, had the breech ring assembly of the 75 mm, and could be mounted in the Sherman's M34 mount. The gun used a shell that used the same projectiles as that of the 3-inch, but a different propellant case design with enough powder to fire a round at 2,600 ft/sec muzzle velocity, identical to the 3-inch gun.[1][2][3]

Two 76 mm T1 guns were made and shipped to Aberdeen Proving Grounds. Tests started in 01 August 1942, with one gun put on a fixed mount while the other was installed in a turret of the M4A1 in place of the 75 mm. Initial tests showed that the gun, 57 caliber in length, was too unbalanced. 15 inches were shaved off from the gun barrel and turned the barrel length to 52 caliber to the detriment of the anti-armour performance, additionally with weight added to the breech ring as a counter weight.[3] On August 17, Aberdeen stated the 76 mm was satisfactory inside the M4 Sherman turret. Classified as Substitute Standard,the 76 mm T1 was approved as the 76 mm Gun M1 and was recommended that the production orders for Shermans be modified for 1,000 Shermans with the 76 mm gun. However, General Jacob Devers from Armored Force did not approve of this plan as the new tanks had not been tested by his board. This led to another trial period, with the 76 mm tried in the newer M34A1 gun mount using the telescopic sight from combat experience in North Africa.[3] The same imbalance issue as previous tests arose, but this was solved by adding an 800 pound counterweight was simply added to the rear of the turret to counterbalance the barrel. Production of the tank started with 12 tanks from the Pressed Steel Car Company for evaluation by Aberdeen, Armored Board, and Tank Destroyer Board. These tanks arrived in 2 February 1943 and tests lasted April 5. The conclusion was that the Armored Board found the constrained space in the turret caused by the larger gun unsatisfactory and the tank was a rushed "quick-fix" design and rejected the tank. This cancelled the type classification and brought the 76 mm tank procurement to a halt.[1]

Ordnance continued to tinker about with their designs and on 3 May 1943, recommended the production of two pilots of an improved 76 mm gun mount for the Sherman. These vehicles were designated as the M4E6 and were fitted with turrets from the T23 of the T20 tank series.[1] Meanwhile, the 76 mm gun was also improved into the M1A1 variant with a changes to the tube contour and a lengthened recoil surface to allow the trunnions to be moved forwards for better balancing of the weapon.[2] The two M4E6 were built by Chrysler, with one sent for evaluations at Aberdeen in July 1943 before being sent to Fort Knox for Armored Board to take a look.[1] The tests proved satisfactory and on 17 August 1943, Armored Board recommended the M4E6 be put into full production for 1,000 units, with even the possibility of completely replacing the 75 mm production with the 76 mm. The latter however was contested by General Alvan Gillem, who took over Devers role in May 1943, by stating the 76 mm's flaw of a lower HE charge compared to the 75 mm (76 mm's 12.37lbs HE shell carries only 0.86lbs explosives whereas the 75 mm's 14.6lbs shell carries 1.47lbs explosives) and its tendency to create dust clouds with its muzzle blast, all for only 1 more inch of armor penetration compared to the 75 mm.[3]

Still, 76 mm production was still in consideration and further improvements were made to the gun. The issue with the muzzle blast was solved with the new long primer ammunition that reduced the smoke left from the burning powder and the installment of a muzzle brake on the gun that diverted the muzzle blast sideways so it does not disturb the dust. The improvement of the muzzle brake led to the request that all 76 mm guns be fitted with a muzzle brake. 76 mm Gun M1 retooled with a threaded end for the muzzle brake were designated the M1A1C, though production of muzzle brakes for these threads did not begin until July 1944, so the threads were covered by a thread protector until muzzle brakes were available. The next model of the 76 mm, the 76 mm Gun M1A2, featured more improvements. The rifling on the gun was tighter with a one turn per 32 caliber rather than the one turn per 40 caliber on previous models, which helped improve ballistics at longer ranges. Every M1A2 design also had a muzzle brake attached.[1][3]

Combat usage

The first batch of 130 M4A1 (76) Shermans were sent to Britain on 10 April 1944, but despite their presence and even reports at the Italian Theater facing some of Germany's newer vehicles like the Panther that the 76 mm was necessary, they were not sent to Normandy on the onset of D-Day. Major General Hugh Gaffey of the 2nd Armored Division advocated for this decision as there were only so few of them available, they were not properly trained on by the troops, and logistic situation would be a mess to supply the ammunition. As such, it was proposed by General W.B. Palmer that the 76 mm be delayed for tank battalions and only specified for such battalions rather than intermingling the 76 mm and 75 mm in mixed units. Either way, not one 76 mm Sherman landed in France in June 1944. Even attempts to interest Third Army on 12 June 1944 fell short as a report went "All of the commanders were relunctant to see it take the place of the 75 mm tank gun in any quantity". The reason for this desire to keep around with the 75 is the belief that the 75 mm could still do the job defeating enemy armour as the newer tanks like the Tiger I have been around since Tunisia and there was no large alarm of a inferiority of their armament. Even the Panther were not taken seriously, not necessarily because it could be handled by the 75 mm, but because it was believed that Panther was a specialized heavy tank allocated in small numbers. It was not until Normandy that the U.S. fighting forces would experience first hand how numerous the Panthers were.[3]

By Normandy in June 1944, criticism from tankers on the ineffectiveness of the 75 mm on the new Panthers came to light. On July 2, Eisenhower relayed the complaints to Ordnance and in July 12, a board was created to determine what weapons were available that could defeat the Panther. The board determined after tests at Isigny that none of the U.S. standard weapons could defeat the Panther from the front, and the 3-inch on the M10 could only do so on the gun mantlet from 200 yards out.[4] Suddenly, the 76 mm Shermans sitting idly at Britain became very sought out and General Bradley of 1st US Army ordered as many of the 76 mm Shermans be sent into France for Operation Cobra. 102 M4A1 (76) tanks arrived to France and became a key part of the operation, marking their debut of combat on 25 July 1944 on the second day. The success of the operation helped vindicate the relevance of the 76 mm Sherman and new 76 mm tank models on the M4 and the M4A3 soon arrived in September 1944. However, the 76 mm Shermans, now combat tested, ended up in another pitfall when they still proved ineffective against the Panther's front. Eisenhower famously remarked on the predicament by saying "You mean our 76 won't knock these Panthers out? Why, I thought it was going to be the wonder gun of the war. Why is it that I'm the last to hear about this stuff? Ordnance told me this 76 would take care of anything the Germans had. Now I find you can't knock out a damn thing with it."[3]

In August 1944, an improved ammunition for the 76 mm started to come in, the T4 (M93) HVAP ammo. With its tungsten ammunition, it could penetrate the Panther by the mantlet up to 1,000 yards out. Though 20,000 were ordered, the supply never kept up with demand and only 2,000 of the HVAP ammo arrived by air. The urge to arm tank destroyers like the M18 Hellcat and M10 with the HVAP left very little for the tanks, with only 1 round available per tank in September. Even by February 1945, the average load of HVAP per tank was five, meaning an acquiring rate of one HVAP per month a tank. A total of 18,000 HVAP came to Europe by March 1945, with 42% of the total being for the 76 mm and the rest for the 3-inch gun. Still, with the ammunition, it didn't do much to prevent the losses experienced in the Ardennes Offensive in December 1944.[3]

The Battle of the Bulge turned a few heads for the 76 mm. Before that, German armour were only experienced in little amounts, with only minor counter-offensives at areas like the Battle of Arracourt. There were divided feelings about the 76 mm due to its decreased HE performance compared to the 75 mm and that the 75 mm has specialized ammo like the white phosphorus round that the 76 did not have. Thus, proposals to completely replace the 75 with the 76 were met with objections. But after the Battle of the Bulge, the criticism changed to the inadequacy of the 75 mm against the German tanks like the Panther and the heavier Tiger II. 12th US Army Group on 29 January 1945 even requested that all US tanks that arrive in Europe be the 76 mm version, refusing anymore 75 mm Shermans.[3]

The 76 mm faced more than a fair share of criticism throughout its life. Promised to give a bigger punch than the 75 mm, it fell short with changing times against improving German armor as it was design created with a mindset of German armour in 1942. Still, as a tank gun, the 76 mm did its job as best it could against the opposition, and was still overall a better gun in several respects that after the war, the 76 mm were retained on the M4A3E8 Sherman. In the 1950s in the Korean War, the 76 mm still proved adequate against the Soviet T-34-85 and no complaints were made on the Sherman's role as an infantry support during the latter stages of the war.[5] Though, as the armament of the evolving U.S. tank force, the 76 mm Gun M1 was succeeded by the much bigger and better 90 mm Gun M3 that would be the armament of the M26 Pershing and its successors.

Images

Additional information (links)

References

  1. 1.0 1.1 1.2 1.3 1.4 Hunnicutt 1978
  2. 2.0 2.1 Hunnicutt 1971
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Zaloga 2003
  4. Moran 2012
  5. Zaloga 2010

Sources

  • Hunnicutt, R.P. Sherman: A History of the American Medium Tank U.S.A.: Feist Publications, 1978
  • Hunnicutt, R.P. Pershing: A History of the Medium Tank T20 Series U.S.A.: Feist Publications, 1971
  • Moran, Nicholas. "The Chieftain's Hatch: US Guns, German Armour, Pt 1." World of Tanks. N.p., 04 Jan. 2012. Web. 25 March 2017. Website
  • Zaloga, Steven. M4 (76mm) Sherman Medium Tank 1943-65 Great Britain: Osprey Publishing Ltd., 2003
  • Zaloga Steven. T-34-85 vs M26 Pershing: Korea 1950 Great Britain: Osprey Publishing Ltd., 2010