Weapon Name- 90mm Chain Gun Mk. III
Round Type- 90×600 mm R
Over-all length- 4.73 m (15 ft 6 in)
Barrel length- 4.60 m (15 ft) L/53
Weight- 12,000 lb
Rate of Fire- 80 RPM
Feed Mechanism- Belt Fed
Round Capacity- 100+
Effective Range- 10 km
Range- 15 km
Accuracy- .3 MOA
Accessories- Picatinny Rails
Quick switch firing mechanism-
Scope/Sights- Scope
Muzzle Velocity- 1200 m/s (3,900 fps)
Firing System- Chain Gun
Miscellaneous/electronic information- The weapon is essentially a 90mm chaingun, which due to it's extreme power and versatility is capable of both anti-tank capabilities and anti-aircraft.
Basic Information
The 90 mm Gun M1/M2/M3 served as a primary heavy American anti-aircraft and anti-tank gun, playing a role similar to the renowned German 88 mm gun. It was 90 mm (3.5 in) in caliber, and had a 4.60 m (15 ft) barrel, 53 calibers in length. It was capable of firing a 90×600 mm R shell 17,823 m (58,474 ft) horizontally, or a maximum altitude of 10,380 m (34,060 ft). The 90 mm Gun was the US's primary anti-aircraft gun from just prior to the opening of World War II into the 1950s, when most anti-aircraft artillery was replaced by guided missile systems. As a tank gun, it was the main weapon of the M36 tank destroyer and M26 Pershing tank, as well as a number of post-war tanks. It was briefly deployed 1943-46 as a coast defense weapon with the United States Army Coast Artillery Corps. With the newer modernized rounds, it is capable of reaching an altitude of approximately 50,000 feet with a 1,200 m/s round, and fullfils a modern niche role being more than effective enough to penetrate the armor of a standard T-72 or T-55 (the most common tanks in the world), while still also having anti-aircraft capabilities. In particular the air bursting abilities which have been developed in recent years allow it to explode in mid-air, and thus allow it to effectively engage light vehicles and infantry despite it's low rate of fire.
In WWII, The M3 was also adapted as the main gun for various armored vehicles, starting with the experimental T7 which was accepted as the 90 mm M3. The test firing of the M3 took place on an M10 tank destroyer in early 1943. The M3 gun was used on the M36 tank destroyer, and the T26 (later, M26) Pershing tank.The M3 fired a M82 APC shot with a muzzle velocity of 2,650 feet per second (800 m/s). However, both the muzzle velocity of the standard M3 gun and the quality of the steel used in the M82 APC shot were inferior to the KwK 43 L/71 88 mm main gun firing its standard APCBC shot used by German forces, with the result that the former's penetration fell far short of the standard projectile fired by the KwK 43 German 88 mm used on the Tiger II/King Tiger tank. As a result, U.S. ordnance provided some T26/M26 tank crews with the 90 mm HVAP (high-velocity, armor-piercing) tungsten penetrator sub-caliber projectile with a muzzle velocity of 3,350 feet per second, or the T33 AP with a re-heat-treated projectile with ballistic windshield and a muzzle velocity of 2,800 feet per second. The HVAP could compete with the KwK 43's penetration performance when firing std. APCBC, but tungsten ammunition was always in short supply, and the T33 which only just made it in service a month before the end of the war still fell far short of the KwK 43's performance.
Because the standard fifteen-and-a-half foot long M3 90 mm main tank gun proved incapable of penetrating the heaviest frontal armor of the heaviest German tanks such as the Tiger II/King Tiger tanks and their seldom-seen Jagdtiger tank destroyer variant, a number of improved versions of the M3 were developed, including the T14 which included a standard muzzle brake and the T15 series. The 21-foot long T15E1 90 mm main gun fired AP T43 shot with an initial muzzle velocity of about 975 m (3,199 ft) per second, later increased to 1,143 m (3,750 ft) per second. Two M26A1E2 "Super Pershing" tanks were equipped with T15-series 90 mm main guns in March 1945. One of these tanks, equipped with a 90 mm caliber T15E1 high-velocity gun firing an AP shot at 1,143 m (3,750 ft) per second made it to the European Theater of Operations and was assigned to the 3rd Armored Division for the testing purposes. Firing HVAP this gun could penetrate 8.5 in (220 mm) of rolled homogeneous armor (RHA) at a range of 1,000 yd (914 m).
With this new and improved round, it was capable of reaching approximately 50,000 feet, and penetrating some of the most powerful armor during the war. As a result of it's incredible power and range, it was able to be used as both an anti-tank and anti-aircraft weaponry, by the explosive rounds shelling the aircraft and peppering them with shrapnel. A somewhat more modernized round can produce approximately 1,200 m/s with a similar round, firing a 10.6 kilogram projectile, that has at least 12 pounds of explosive filler. Driving bands are used to help reduce the friction of the round on the rifling and to help increase the longevity of the rifle, and the rounds are furthermore coated in molybdenum disulfide to help reduce the friction of the barrel. The barrel itself is a cobalt chrome polygonal flow formed barrel with a gain twist, that helps to reduce chamber pressures by reducing the amount of torque initially experienced in the barrel. All of this combined helps to substantially reduce the wear on the barrel and stresses experienced by the gun, which allows the barrel to last substantially longer than it would otherwise. The weapon has approximately a 2,000 round life, which is relatively short for it's rate of fire, but still very effective.
The rounds are approximately 50.4 pounds fully loaded, and the standard carry load is around 300 rounds for most vehicles, however it can carry more. The round fullfills a niche role in that it can no longer penetrate the armor of the best tanks, but is far more powerful than is needed to destroy most light tanks. Given the proliferation of medium battle tanks in the world however such as the T-72 and T-55, and it's ability to function as an anti-aircraft weapon, it in conjunction with other weapons can reliably fill a role that many weapons cannot. The weapon almost always has a muzzle break and a hydraulic recoil buffer to help reduce the recoil of the weapon, which allows it to be substantially smaller than it would otherwise need to be. The chain gun mechanism is based on the 57mm bofors, but is substantially smaller due to it's lower rate of fire.
