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75 mm gun M2–M6
75 mm gun M2–M6
75 mm gun M2–M6
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An M3 is lifted out of a Sherman tank at 5th Indian Division's tank workshop near Taungtha, Burma, 29 March 1945
A restored Mitchell aircraft showing a 75 mm M5 gun below the four machine guns

The 75 mm gun, models M2 to M6, was the standard American medium caliber gun fitted to mobile platforms during World War II. They were primarily mounted on tanks, such as the M3 Lee and M4 Sherman, but one variant was also used as an air-to-ground gun on the B-25 Mitchell medium bomber aircraft. There were five main variants used during the war: M2, M3, M4, M5 and M6.

They were considered the standard American tank guns. The M2 and M3 were used on the M3 medium tank, the M3 was used on the M4 Sherman tank, and the M6 was used on the M24 Chaffee light tank. The M3 was also used on M7 medium tank.

The M5 variant was fitted on some North American B-25 Mitchell medium bomber aircraft.[1]

History

[edit]
M2 75 mm gun as mounted in medium tank M3

The 75 mm tank gun has its origins in the January 1937 specification for a light anti-aircraft gun T6 which would have supplemented heavy 3-inch guns and used the same range of 75x350R ammunition as the 75 mm field gun M1897. After the gun, which featured a 31-caliber barrel and a sliding block breech, failed the trials, it was reused in mid-1940 to develop the T7 tank gun.[2]

British tanks in the early years of World War II relied on high-velocity ordnance derived from anti-tank guns, such as the 40 mm calibre Ordnance QF 2 pounder and, later, 57 mm calibre Ordnance QF 6 pounder, for their primary armament. According to the Royal Armoured Corps doctrine, they were not supposed to fire HE shells, which turned out to be a great disadvantage. Post-war, the UK's Tank Museum credited the US 75mm gun as "America's most important contribution to tank warfare" because of its ability to combine good (for the time) AP and HE performance. They believed that the American observers working with the British before Dunkirk had appreciated the effectiveness of such a dual purpose weapon, and so it was made a prime requirement for US tank production.[3]

After experiencing the effectiveness of the American 75 mm tank guns in the infantry support role, the British opted to adopt the American caliber and ammunition by the expedient of boring-out the 6 pounder tank gun to make the Ordnance QF 75 mm. By 1944, this had become the standard British tank gun, equipping the Cromwell tank and Churchill tank for the campaigns in northwest Europe.

Ammunition

[edit]

The primary round was the 6.76 kg (14.9 lb) M48 high explosive round, which travelled at 594 m/s (1950 ft/s) using the supercharge from the longer barreled M3 and contained 1.5 pounds (680 g) of TNT filling (2845 kilojoules of explosive energy) and a choice of two fuzes, the super quick (SQ) and the delay (PD), which had delays of 0.05 and 0.15 seconds respectively. SQ was the standard setting, with PD used against structures, gun positions or lightly protected vehicles. The field gun origins of the ordnance and ammunition ensured that the M2/3/6 series HE round was highly effective for its caliber. The M48 was available in two versions, standard and supercharge, which had an increased propellent charge for greater muzzle velocity (1,885 ft/s (575 m/s) vs. 1,470 ft/s (450 m/s)) and range (2,300 yards greater) using the M2 gun. The M3 gun with a longer barrel had an muzzle velocity of 594m/s (1950 ft/s) Vs 463m/s (1520ft/s)

Other rounds fired by the 75mm tank guns included the T30 canister shot for use against troops in the open at short range. This, which was essentially a giant shotgun shell full of large numbers of steel balls, was used primarily in the Pacific. There was also the M89 base-ejecting hexachloroethane (HC) smoke round and the M64 white phosphorus (WP or "Willy Pete") round, which proved highly effective in the bocage fighting around Normandy.[citation needed] Finally, there were two different armor-piercing rounds.

The first armor-piercing round was the 6.32 kg (13.9 lb) M72 AP-T, a plain uncapped armor-piercing round whose performance dropped off as range increased due to poor aerodynamics. The M72 was replaced by the 6.63 kg (14.62 lb) M61 armor-piercing ballistic capped high explosive with tracer (APCBC-HE-T) shell. The blunt armor-piercing cap, made of a softer metal, helped to prevent shell shatter at higher velocities and against sloped and face-hardened armor. The aerodynamic ballistic cap acted as a windscreen and improved ballistic performance, maintained velocity, and hence increased penetration at longer ranges. Once the projectile had penetrated the target, a small explosive charge contained in a cavity at the base of the shell would detonate, shattering the shell and increasing damage inside the enemy vehicle. The tracer helped in the aiming of a second shot. In practice, the majority of M61 rounds were shipped without the explosive filler.[citation needed]

The M61A1 used an improved method of attaching the ballistic cap to the shell. The M61 had a muzzle velocity of 617 m/s (2024.28 ft/s) and was able to penetrate 81 millimetres (3.2 in) of rolled homogeneous armor plate at 0° from vertical at 500 yards range, and the 50 mm front plating of the Panzer III and IV Ausf. F2 current in early 1942 at 1,500 m.[4] However, in March 1942, the Germans introduced the Ausf. G version of the Panzer IV, armed with the KwK 40 gun, and with frontal hull armour of 80 mm. This was somewhat compensated by the M4 Sherman's improved armor over the earlier M3 Lee making up for the 75mm M3's diminishing battlefield dominance; the German weapons testing agency Wa Pruef 1 estimated that the M4's standard 56º-angled glacis was impenetrable to the KwK 40 from 100 m when standing at a 30-degree side angle, while the 75 mm M3 could penetrate the Ausf G's hull in the same situation.[4]

Variants

[edit]
An M3 Grant with a 75 mm gun
An M4 Sherman with a 75 mm gun M3
An M24 Chaffee with a 75 mm gun M6

T6

Experimental anti-aircraft gun based on the M1897 field gun.[citation needed] The barrel was shortened from 36 to 31 calibers, and the Nordenfelt screw breech replaced with the sliding block breech.

T7 / M2

Adaptation of the T6 for tank gun role. Used on the early M3 Lee.

  • Barrel length: 31 calibers
  • Muzzle velocity: 588 m/s (1,929 ft/s) with M72 AP shell
  • Maximum Rate of Fire (ROF): 20 rounds per minute[5]

T8 / M3

Longer derivative of the M2. Equipped American and British vehicles such as the M4 Sherman, the later models of the M3 Lee and the Churchill III/IV NA75 (scavenged from Sherman tanks in the North African theatre). The US Army also experimented with mounting the M3 on various wheeled carriages for use as anti-tank gun, but the program was cancelled due to a lack of requirement.[6]

  • Barrel length: 40 calibers (3 m)
  • Muzzle velocity: 619 m/s (2,031 ft/s) with M72 AP shell
  • Maximum Rate of Fire (ROF): 20 rounds per minute[5]

M4

The 75 mm aircraft gun M4 is a modification of the M3 gun found in medium tanks. It differs from the M3 gun, only in having a seat for the spline machined in the tube. It was mounted on the M6 mount.

T13E1 / M5

A lightweight version of the M3 with a lighter thin-walled barrel and a different recoil mechanism of the concentric hydrospring type (similar to the modern M256 smoothbore gun) that was used in the Douglas A-26 Invader and the North American B-25H Mitchell bombers. It uses the same ammunition and has the same ballistics as the M3.

M6

A version derived from the T13E1 for the M24 Chaffee.

  • Barrel length: 39 calibres (2,92 m)
  • Muzzle velocity: 619 m/s (2,031 ft/s) with M72 AP shell
  • Maximum Rate of Fire (ROF): 20 rounds per minute[5]

Penetration comparison

[edit]
Penetration of armor in mm at 30 degrees from vertical[7]
Gun type Ammunition Target 500 yards 1,000 yards 1,500 yards 2,000 yards
75mm L/31 (M2) APC M61 RHA 60 55 51 46
75mm L/31 (M2) AP M72 RHA 60 53 46 38
75mm L/31 (M2) APC M61 FHA 69 60 55 48
75mm L/31 (M2) AP M72 FHA 58 46 33 25
75mm L/40 (M3/M6) APC M61 RHA 66 60 55 50
75mm L/40 (M3/M6) AP M72 RHA 76 63 51 43
75mm L/40 (M3/M6) HVAP T45 RHA 117 97 79 64
75mm L/40 (M3/M6) APC M61 FHA 74 67 60 54
75mm L/40 (M3/M6) AP M72 FHA 66 53 41 33
Estimated penetration figures (90 degrees)[8][9]
Gun type Ammunition Target Muzzle velocity Penetration (mm)
100 m 250 m 500 m 750 m 1000 m 1250 m 1500 m 1750 m 2000 m 2500 m 3000 m
75mm L/31 (M2) APC M61 FHA 563 m/s (1,850 ft/s) 92 89 84 79 75 71 67 63 59 53 47
75mm L/31 (M2) APC M61 RHA 563 m/s (1,850 ft/s) 78 76 72 68 65 61 58 55 52 47 42
75mm L/31 (M2) AP M72 FHA 563 m/s (1,850 ft/s) 82 76 67 59 52 45 40 35 31 24 19
75mm L/31 (M2) AP M72 RHA 563 m/s (1,850 ft/s) 95 90 81 73 66 60 54 49 45 36 30
75mm L/40 (M3/M6) APC M61 FHA 618 m/s (2,030 ft/s) 102 99 95 90 86 82 79 75 72 65 60
75mm L/40 (M3/M6) APC M61 RHA 618 m/s (2,030 ft/s) 88 85 81 77 73 69 65 62 59 53 47
75mm L/40 (M3/M6) AP M72 FHA 618 m/s (2,030 ft/s) 91 85 75 66 58 51 45 40 35 27 21
75mm L/40 (M3/M6) AP M72 RHA 618 m/s (2,030 ft/s) 109 102 92 84 76 68 62 56 51 41 34

See also

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Weapons of comparable role, performance and era

[edit]

References

[edit]

Sources

[edit]
  • Zaloga, Steven J., Brian Delf – US Anti-tank Artillery 1941–45 (2005) Osprey Publishing (New Vanguard 107), ISBN 1-84176-690-9.
  • Hunnicutt, R P (1978). Sherman, A History of the American Medium Tank. Presidio Press. ISBN 1626548617.
  • TM 9-2800 Standard Artillery and Fire Control Material (dated February 1944)
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

75 mm gun M2–M6

View on Grokipedia
from Grokipedia
The 75 mm gun M2–M6 was a series of rifled, semi-automatic guns developed by the Ordnance Department during , adapted from the French Canon de 75 mm modèle 1897 for use as primary armament on American armored vehicles. These medium-caliber weapons featured a drop-block breech mechanism, vertical sliding , and hydro-pneumatic system, with overall lengths ranging from 91.75 inches (M2) to 118.38 inches (M3), enabling muzzle velocities up to 2,030 feet per second for armor-piercing rounds and maximum ranges exceeding 14,000 yards. They were designed for support, balancing high-explosive capability against anti-tank penetration, and achieved a practical of 6–20 rounds per minute depending on conditions. Development of the M2–M6 series began in the late as the U.S. Army sought to modernize its tank armament beyond the inadequate 37 mm M5/M6 guns, which struggled against emerging German and Japanese armor. The model, standardized in 1941, was a direct adaptation of the M1897's tube and chamber, shortened for mounting in the of the interim M3 (), prioritizing rapid production to address urgent needs for a high-explosive weapon capable of 1,850 feet per second with armor-piercing shells. Subsequent variants improved performance: the M3, introduced in 1942, extended the barrel to 39.3 calibers for better velocity (up to 2,030 feet per second) and penetration, fitting the fully rotating turret of the ; the M5 was a lightweight aircraft version for ground-attack roles; and the M6, finalized in 1944, optimized for light tanks like the with a 39-caliber barrel and enhanced stabilization. These evolutions reflected iterative testing at , focusing on reliability in mobile warfare without requiring entirely new designs. In combat, the M2–M6 guns armed over 50,000 Sherman tanks and thousands of light vehicles, proving decisive in Allied offensives from to the Pacific theater due to their versatility with ammunition types—including the 14.96-pound M61 armor-piercing capped () shell for penetrating up to 61 mm (2.4 inches) of armor at 500 yards and 30° obliquity, the 14.70-pound M48 high-explosive (HE) shell for infantry suppression, and chemical or smoke variants for tactical flexibility. Early M2-equipped M3 Lees provided crucial in the 1942–1943 campaigns but were limited by hull mounting and low velocity; the M3's adoption in Shermans enabled superior turret traverse (up to 360 degrees) and stabilization for firing on the move, contributing to tactical successes like the and , though later models faced challenges against heavier German Panthers and Tigers, prompting shifts to 76 mm guns. The M6's deployment on the M24 from 1944 onward restored effectiveness with a maximum range of 14,000 yards and up to 20 rounds per minute. Post-war, surplus M3 guns influenced allied designs and remained in limited service until the .

Development and History

Origins and Early Development

The development of the 75 mm gun series began in the late 1930s amid growing concerns over air and armored threats. In January 1937, the U.S. Army Ordnance Department issued a specification for a light anti-aircraft gun designated T6, aimed at providing mobile defense to supplement the existing heavy 3-inch anti-aircraft guns. This prototype was heavily influenced by the French 75 mm Mle 1897 field gun, a World War I-era design that the U.S. had produced in large numbers and modified for its own use. The T6 incorporated a semi-automatic vertical sliding breech mechanism to enable a sustained rate of fire suitable for engaging low-flying aircraft. Initial testing of the T6 at Aberdeen Proving Ground highlighted issues with recoil stability and overall performance in anti-aircraft roles, leading to its reevaluation as European conflicts demonstrated the rising importance of anti-tank capabilities. By mid-1940, with reports of German armored successes influencing U.S. priorities, the Ordnance Department repurposed the T6 design for ground combat, redesignating it as the T7 anti-tank gun. Key modifications included adjustments to the barrel profile and recoil system to enhance armor-piercing effectiveness while maintaining compatibility with the Mle 1897's ammunition, allowing for both armor-piercing and high-explosive rounds. The push toward a dual-purpose role accelerated in 1940, driven by British requirements for a versatile weapon that could support with high-explosive fire while countering tanks. This led to further refinements in the T7's breech and sighting systems during trials, emphasizing rapid loading and accuracy for both anti-tank and missions. The T7 was standardized as the 75 mm Gun in September 1940, paving the way for its integration into early medium tanks like the , with production beginning that month. These early iterations established the foundational design for subsequent M3 through M6 variants, balancing mobility, , and adaptability.

Adoption and Production

The U.S. Army formally adopted the 75 mm gun M2 in as a for anti-tank roles, with its integration into armored vehicles accelerating amid urgent demands for equipping the . This adoption was driven by the need for a versatile capable of firing both armor-piercing and high-explosive rounds, addressing limitations in earlier 37 mm armaments. The M2's design, derived from interwar modifications to the French 75 mm M1897 field gun, allowed rapid scaling for tank mounting in the M3 Lee/Grant series, with the first armed tanks entering production by early 1941 to meet wartime mobilization goals. British requirements played a pivotal role in prioritizing the 75 mm caliber for subsequent U.S. tank designs, particularly the , as Allied agreements emphasized vehicles with effective infantry support capabilities beyond the British 2-pounder gun's anti-tank focus. In response, U.S. production lines adapted the M3 variant of the gun for the Sherman turret starting in 1942, enabling British forces to receive 75 mm-armed Shermans that enhanced their operations in and . The British further adapted the design into their Ordnance QF 75 mm gun, re-chambering it for British cases while retaining U.S. projectiles to fit Sherman tanks, which facilitated widespread Allied use and simplified supply chains. Manufacturing of the M2–M6 series was centered at Watervliet Arsenal, the U.S. Army's primary cannon facility, with output ramping up significantly from late 1940 onward to support tank destroyer vehicles, self-propelled artillery, and aircraft mounts alongside ground applications. By 1945, total production across variants exceeded 60,000 units, reflecting the gun's role as a cornerstone of American medium artillery during the war. Additional contractors contributed to component fabrication, but Watervliet handled final assembly to ensure uniformity. Logistical integration benefited from ammunition compatibility with existing 75 mm stocks, as the M2–M6 series shared chamber dimensions and projectile types with the M1897 field gun and M3 howitzer, enabling reuse of interwar inventories for fixed complete rounds like armor-piercing M61 and high-explosive M48. This standardization mitigated supply strains early in the war, though challenges arose from initial shortages of modern fuzes and penetrators, requiring adaptations such as sourcing French components for British-operated units. Overall, these factors ensured the gun's seamless incorporation into U.S. and Allied forces, supporting operations from 1942 through the European and Pacific theaters.

Design

Technical Specifications

The 75 mm gun M2–M6 series was chambered in 75 mm (2.95 in) , providing a balance of firepower and compatibility with existing stockpiles. The baseline design incorporated a barrel length of 28.5–40 s, with bore lengths ranging from approximately 2.13 m for early models to 2.81 m in later iterations, optimizing velocity while fitting within turret constraints. Barrel assembly weights ranged from 410 lb (M6 complete) to 893 lb (M3 complete), with tube weights around 611 lb for the M2, facilitating mounting on mobile platforms. The breech employed a semi-automatic vertical sliding block mechanism, which allowed for rapid reloading by automatically ejecting spent casings and positioning the block for the next round. This design supported a maximum of 20 rounds per minute, limited primarily by crew efficiency and ammunition supply. Muzzle velocities for standard armor-piercing rounds reached 588 m/s (1,930 ft/s) in shorter-barrel variants and up to 619 m/s (2,030 ft/s) in longer ones, influencing overall ballistic performance. The system featured a hydrospring , combining hydraulic with spring return to manage the gun's impulse and return it to battery quickly, typically absorbing 11.5 inches (292 mm) of travel. Variant-specific adjustments to barrel length and weight are addressed in the Variants section.
SpecificationBaseline ValueNotes
75 mm (2.95 in)Standard across series
Barrel Length (calibers)28.5–40Bore length 2.13–2.81 m; varies by model (e.g., M2: 28.5 cal, M3/M6: 37.5 cal)
Weight (barrel assembly)410–893 lb (186–405 kg)Complete gun weights; e.g., M2: 783 lb; M3: 893 lb; M6: 410 lb
Breech MechanismSemi-automatic vertical sliding blockHorizontal sliding wedge in later mounts
20 rounds/minMaximum
(AP round)588–619 m/s (1,930–2,030 ft/s)Dependent on barrel length and charge
SystemHydrospring recuperator~11.5 in (292 mm) travel; hydraulic and spring elements
N/ARoutine maintenance includes inspection for throat erosion and rifling degradation, daily cleaning, , and bore gauging

Construction and Features

The 75 mm guns through M6 were constructed with a monobloc barrel, a choice that provided structural integrity under high pressures while simplifying and for mobile applications. The vertical sliding , often described as a drop-type mechanism, was selected for its reliability in and mounts, allowing semiautomatic operation that automatically opened upon firing to eject the spent case, thereby supporting sustained rates of fire in combat scenarios. Key operational features included telescopic sights integrated with periscope types M1 or M3, enabling the gunner to acquire targets from within the protected turret environment while providing reticles for range estimation and lead adjustments. These sights were battery-operated for low-light visibility, emphasizing the guns' adaptability for both daylight and nocturnal engagements. The design also incorporated a key in the breech ring to prevent rotation between the gun tube and mount, ensuring precise alignment and operational stability during traversal. Innovations across the series addressed mounting constraints and performance needs; early models like the featured a shorter barrel to fit within the limited space of initial turrets, such as those on the M3 medium , while subsequent variants like the M3 and M6 extended the barrel length to improve projectile velocity without altering the core chamber dimensions. This modularity maintained compatibility with existing U.S. 75 mm fixed ammunition stocks, allowing seamless integration of high-explosive and armor-piercing rounds for versatile battlefield roles. Safety and reliability were prioritized through bore-safe fuze mechanisms that prevented premature detonation if a round hung up in the chamber, complemented by an oil lock system in the cylinders to buffer excessive movement and reduce exposure to malfunctions. Regular lubrication and inspection protocols further mitigated misfires by ensuring smooth extractor function and breech operation.

Variants

Ground Mount Variants

The 75 mm gun M2 was the initial ground-mounted variant, featuring a relatively short 28.5-caliber barrel with a bore length of 84 inches, designed for installation in the hull of the and Grant medium tanks. This mounting allowed for limited traverse of 15 degrees left and right, prioritizing ease of production and integration into the tank's design during early wartime needs. Optimized for close-support roles, the M2 emphasized high-explosive projectiles to engage and soft targets effectively, with a weight of 783 pounds and a semi-automatic vertical sliding-wedge in Mount M1. The M3 variant addressed limitations of the M2 by extending the barrel to 37.5 calibers (110.63 inches bore length), increasing while maintaining compatibility with existing for balanced anti-tank and high-explosive capabilities. Mounted in the fully traversable turret of the series using Mount M34 or M34A1, it weighed 893 pounds and featured a horizontal sliding-wedge breechblock, enabling a maximum up to 20 rounds per minute. This configuration made the M3 the standard armament for the Sherman, supporting versatile combat roles in operations. The M6 variant retained the 37.5-caliber barrel length of the M3 (110.63 inches) but utilized a lighter tube construction weighing only 410 pounds, along with a modified horizontal sliding-wedge in Mount M64 and a shallower breech recess for reduced travel. Fitted into the turret of the , it shared the M3's to provide potent firepower without compromising the vehicle's emphasis on speed and mobility. This setup allowed the Chaffee to carry 48 rounds while maintaining a low and agile performance in forward areas.

Aircraft Mount Variants

The aircraft mount variants of the 75 mm gun series were specialized adaptations designed to address the unique constraints of fixed-wing installations, such as reduced weight for improved performance and simplified mechanisms to ensure compatibility with structures and levels. These variants prioritized manual loading and forward-firing configurations for and anti-tank missions, with modifications including thinner barrels and adjusted breech systems compared to ground-based models. The M4 variant represented an early lightweight iteration, a modification of the M3 gun adapted for use, featuring a vertical sliding and a tube screwed into the breech ring. It featured a machined seat on the gun tube for a muzzle cover spline ring and a modified breech operating shaft for easier installation and removal. Weighing approximately 893 pounds in full assembly, the M4 included two cylinders—one above and one below the tube—for controlled 21-inch , filled with lubricating oil to dampen forces during flight. This variant was mounted in the nose of the North American B-25G Mitchell medium bomber, enabling low-level attacks with its 37.5-caliber bore length and of around 1,970 feet per second. It was also adapted for use in the ground-attack . The M5 variant further refined the design for broader bomber applications, with enhancements to the recoil system and overall integration for twin-engine platforms like the B-25 Mitchell. It was installed in the medium bomber, either as a single nose-mounted gun in the B-25G model or in refined single configurations in the B-25H for strafing and anti-tank roles, often paired with multiple .50-caliber machine guns for combined fire. The M5 maintained a focus on reduced weight—targeting under 400 pounds for the core gun assembly—and a simplified drop-block breech for airframe compatibility, allowing pilots to aim via integrated sights while compensating for recoil-induced airspeed loss of about 20 knots per shot. Production of these aircraft-specific guns was limited to roughly 500 units, constrained by the specialized needs of A-20 and B-25 modifications and the shift toward machine-gun-heavy strafers later in the war.

Ammunition and Ballistics

Projectile Types

The 75 mm gun M2–M6 fired fixed ammunition consisting of projectiles assembled to brass cartridge cases measuring 75×350 mm R, with the propelling charge contained within the case and consisting of single-perforated smokeless powder granules weighing approximately 2.1 pounds for the full charge in the M3 variant. These rounds were designed for versatility in armored vehicle and aircraft applications, supporting roles from anti-tank engagements to infantry suppression and obscuration. Armor-piercing projectiles were the primary anti-tank option, exemplified by the M72 AP-T round, which featured a 6.32 kg solid body with an integrated base-detonating tracer for flight observation and targeting adjustment. The M61 APCBC-HE-T variant improved upon this with a soft armor-piercing cap and ballistic cap for better performance against angled armor and reduced likelihood, while incorporating a small high-explosive burster and tracer. High-explosive projectiles provided general support against unarmored targets, with the M48 HE shell weighing 6.67 kg and filled with 0.68 kg of TNT for fragmentation and blast effects upon point-detonating activation. Other specialized types expanded tactical options, including the T30 canister round, which functioned as an anti-personnel munition by dispersing steel pellets over a wide area at short ranges to neutralize exposed . The M66 was a round using a with base-detonating (M62) for armor penetration, primarily developed for the 75 mm pack but tested and used in limited numbers with guns. Smoke rounds encompassed the M64 WP, a 6.3 kg filled with for generating dense screening and secondary incendiary effects, as well as base-ejection variants like the M89 for sustained, low-velocity deployment without expulsion of the casing.

Ballistic Data

The 75 mm gun M2–M6 exhibited varying ballistic performance across its variants, primarily influenced by barrel length and configuration. For the M3 barrel, the of the M61 APCBC projectile reached 619 m/s, providing effective flat-trajectory fire for anti-armor roles. Similarly, the M48 HE shell achieved a of 604 m/s when fired under standard conditions with supercharge, balancing explosive payload delivery with manageable recoil. Maximum range for these projectiles extended to 13,000–14,000 yards under optimal conditions, limited by the gun's capabilities up to 90 degrees in certain ground and mounts, allowing for both direct and applications. Effective engagement ranges typically fell within 13,000 yards for high-angle trajectories, emphasizing the gun's versatility in mobile platforms. The gun's propellant system utilized single-base powder, with incremental charges (normal and super) permitting velocity adjustments to suit mission requirements—normal charges for high-explosive rounds to reduce barrel wear, and super charges for armor-piercing projectiles to enhance penetration potential.

Performance and Comparison

Penetration Capabilities

The penetration capabilities of the 75 mm gun M2–M6 were primarily determined by the variant's barrel length and , with the M3 and M6 models providing superior performance over the shorter-barreled M2 due to higher projectile speeds. The standard armor-piercing round, the M61 APCBC, offered balanced penetration and post-penetration effects, while factors such as impact angle and target material significantly influenced outcomes. Data below reflects 50% penetration probability against homogeneous armor plate.
Range (yards)M2 (L/31 barrel, APCBC M61, 30° obliquity, mm RHA)M3/M6 (L/40 barrel, APCBC M61, 30° obliquity, mm RHA)
06471
2505869
5005364
1,0004861
1,5004156
2,000N/A50
Penetration decreased notably at oblique angles due to the increased line-of-sight thickness of the armor, with 30-degree obliquity typically reducing effective penetration by 20-30% compared to perpendicular impacts. Against face-hardened armor, results were slightly lower for the M61 round, achieving approximately 69 mm at 500 yards for the M3/M6 variant. The gun excelled against side armor, such as the Panzer IV's 30 mm plates or the Panther's 40-50 mm side sections, allowing reliable defeats at combat ranges up to 1,000 yards when striking at favorable angles. Despite these strengths, limitations emerged against heavily armored late-war targets; the M3/M6's maximum penetration of approximately 90 mm at point-blank perpendicular impact proved inadequate for the Tiger I's frontal armor (100 mm thick, sloped at 9 degrees for an effective thickness of approximately 101 mm) beyond 500 yards under typical engagement conditions.

Comparative Analysis

The 75 mm M3 gun, while sharing the same caliber as the German , exhibited distinct performance characteristics due to differences in design priorities. The M3 achieved a of approximately 619 m/s for its armor-piercing rounds, significantly lower than the KwK 40's 790 m/s, which prioritized anti-tank penetration at longer ranges. This lower velocity on the M3 allowed for a slightly more effective high-explosive (HE) shell, with greater filler capacity (around 0.70 kg) compared to the KwK 40's HE round (approximately 0.68 kg), enhancing its utility against infantry and soft targets despite the German gun's superior anti-armor role. In comparison to the British Ordnance QF 75 mm tank gun, the American M3 series represented a direct adaptation for applications, derived from similar pre-war concepts but optimized for lighter weight in vehicle mounts. Penetration performance was broadly comparable between the two, with both achieving similar armor defeat at typical combat ranges using equivalent , though the M3's design emphasized reliability in high-volume production for Allied forces. Against the Soviet 76 mm ZiS-3 divisional gun, the 75 mm M3 demonstrated inferior anti-tank capabilities, as the ZiS-3's slightly larger caliber and comparable (680 m/s) enabled greater armor penetration—up to 53 mm at 2,000 meters versus the M3's roughly 40 mm at similar ranges. However, the M3 offered advantages in HE performance for close infantry support, though the ZiS-3 countered with a heavier HE shell (filler weight of 0.71 kg in the OF-350 projectile) that provided superior blast effects against personnel and fortifications, aligning with Soviet doctrinal emphasis on versatile field artillery roles. By 1943, the role of the 75 mm M2–M6 series had evolved from a primary anti- in early medium tanks like the to a general-purpose gun in the , balancing armor defeat with enhanced HE capabilities to support operations against increasingly diverse threats. This shift reflected broader U.S. tactical adaptations, prioritizing support and multi-role flexibility over specialized long-range tank killing, as evidenced by its retention despite the introduction of higher-velocity alternatives.

Operational History

Use in Armored Vehicles

The 75 mm gun M2–M6 was primarily mounted in the M4 Sherman medium tank, where it served as the standard armament for the vast majority of production models, comprising approximately 78% of the total 49,234 Shermans built during World War II. This integration allowed the Sherman to function effectively in combined arms operations, leveraging the gun's high-explosive (HE) rounds to provide direct fire support to infantry units, suppressing enemy positions and fortifications while maintaining armored mobility. The M3 variant of the gun, adapted for tank use with a longer barrel for improved velocity, was fitted into the M34 gun mount, enabling a full 360-degree traverse and elevation from -10 to +25 degrees, which supported versatile engagement of both ground and low-flying aerial targets. In tank destroyer roles, the 75 mm M3 gun was installed on the (GMC), an expedient vehicle produced in limited numbers for early wartime needs, featuring an open-top pedestal mount that maximized gun elevation up to +30 degrees for defensive ambushes against approaching armor. This design prioritized rapid deployment and high-angle fire over crew protection, aligning with initial U.S. concepts tested in , where the M3 GMC equipped battalions before being phased out in favor of more advanced platforms. The open-top configuration facilitated quick reloading and observation but exposed crews to small-arms fire and shrapnel, influencing later doctrinal shifts toward enclosed turrets. U.S. armored doctrine emphasized mobility and indirect engagement over head-on duels, positioning the 75 mm-armed Sherman as a fast-moving support weapon capable of outmaneuvering and flanking medium German tanks like the and IV, which it could reliably penetrate at combat ranges under 1,000 yards using armor-piercing rounds. Against heavier Panthers and Tigers, the gun's effectiveness diminished, requiring reliance on numerical superiority, coordinated , and air support to achieve breakthroughs, as outlined in 1943-1944 field manuals that stressed massed tank assaults in combined-arms teams. Following 1943 combat experiences in and , field modifications to 75 mm-equipped vehicles included upgrades to the M34 gun mount for improved telescopic sights, such as the addition of direct-vision periscopes and optics to enhance accuracy during rapid advances, and enhanced turret ventilation systems to mitigate gun fumes and crew fatigue in prolonged engagements. These adaptations, often performed by ordnance units in theater, addressed early limitations in fire control and habitability without requiring full factory overhauls, allowing continued service of existing stocks amid production demands for newer 76 mm variants.

Use in Aircraft

The 75 mm M4 cannon was installed in the nose of the B-25G Mitchell medium bomber starting in , replacing the bombardier and copilot positions to accommodate the weapon's length and management requirements, with the barrel extending through a ventral for firing. This adaptation was driven by the need for enhanced ground attack capabilities in low-level missions, where the cannon provided support against enemy positions. The installation demanded significant modifications, including reinforced structure to handle the gun's 2,000-foot-per-second and resulting backward force, which could reduce the aircraft's speed by up to 20 knots during firing. In the B-25H variant, the lighter T13E1 (M5) 75 mm cannon succeeded the M4, maintaining the nose-mounted configuration but with reduced weight to mitigate ongoing structural stresses, while augmenting the armament with additional .50-caliber machine guns for coordinated fire. These aircraft were employed primarily for in the Pacific and Mediterranean theaters, targeting soft ground installations, troop concentrations, and light armor such as transport vehicles and unarmored ships. In the Mediterranean, B-25 squadrons of the Twelfth Air Force, including those equipped with 75 mm cannons, conducted skip-bombing runs and against Axis supply lines, contributing to the sinking of over 200 vessels and disrupting rail networks during operations like Strangle and , with the cannon proving effective against lightly defended coastal targets. Pacific deployments, including U.S. Marine Corps PBJ-1G variants, focused on low-altitude strikes against Japanese airfields and barges, where hits from the 75 mm shells could disintegrate soft targets like parked aircraft or wooden vessels. Operational challenges included severe recoil that stressed the , often causing rivets to pop and requiring frequent , as well as accuracy degradation from compass deviations of up to 15 degrees and the difficulty of aiming at high speeds exceeding 250 mph. The manual loading process limited firing to short bursts of 3-4 rounds per 30-second attack run, with pilots typically expending only 7-9 shells per to conserve and avoid excessive vibration. These limitations confined the cannon's role to specialized ground support rather than sustained engagements, and many units in the Pacific eventually replaced it with multiple machine guns for higher-volume fire. Ammunition loads varied by mission but generally carried 11-21 rounds per gun, prioritizing high-explosive (HE) shells weighing approximately 15 pounds for area suppression against soft targets, supplemented by armor-piercing (AP) rounds for anti-vehicle strikes on light armor. The HE projectiles delivered an approximately 1.5-pound TNT payload, effective at ranges up to 2 miles for shattering unarmored structures, while AP variants penetrated thin plating on trucks or small boats.

Notable Combat Engagements

The 75 mm M3 gun mounted on tanks proved effective during in the of 1942–43, where it engaged Axis light and medium tanks like the at ranges up to 2,000 yards using M61 APCBC shells. These guns enabled Allied forces to destroy enemy armor in key actions, such as the Second Battle of El Alamein, contributing to the Axis retreat across . However, Shermans were highly vulnerable to German 88 mm guns in ambushes, as demonstrated on February 14, 1943, when the U.S. 1st Armored Division lost 37 of 44 tanks to concealed 88 mm fire and early encounters. In the Normandy Invasion of 1944, M4 Sherman tanks armed with the 75 mm M3 gun played a crucial role in bocage fighting, using their penetration capabilities to decisively counter German ambushes in hedgerow terrain. Equipped with improvised "Rhino" hedge-cutters, these Shermans breached dense hedgerows to expose and destroy concealed Panzer IVs and anti-tank positions at point-blank range, as seen in the 747th Tank Battalion's advance near St. André-de-l'Épine on August 5, 1944, where they executed a 3,000-yard push without losses. The gun's high-explosive shells effectively suppressed infantry and fortifications hidden behind the bocage, turning potential kill zones into Allied breakthroughs. During the Pacific Theater in 1944–45, B-25 Mitchell bombers fitted with the 75 mm M5 gun provided vital air support against Japanese fortifications in the , particularly in operations like . These nose-mounted cannons, combined with forward-firing .50 caliber machine guns, targeted bunkers and strongpoints during low-level strikes, aiding ground forces in recapturing areas like by demolishing entrenched positions. The 75 mm's ability to fire armor-piercing rounds at up to two miles enhanced the B-25's role in suppressing Japanese defenses, though its use waned due to operational challenges. By late war, the 75 mm gun's limitations became evident in the Offensive () of December 1944, where Sherman tanks struggled against King Tiger heavy tanks whose thick frontal armor often deflected 75 mm shells. In engagements along narrow roads, the few deployed Tiger IIs withstood multiple hits from 75 mm guns, forcing U.S. crews to rely on flanking maneuvers or superior numbers, which shook morale and highlighted the weapon's obsolescence against upgraded German armor. This vulnerability accelerated the shift to 76 mm gun upgrades on Shermans, improving penetration and restoring offensive capability in subsequent operations.

References

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