During the Second World War, there was a steady trend towards an increase in the caliber of anti-tank artillery. So, the American army entered the war with 37 mm cannons, and ended it with 76 and 90 mm guns. The increase in caliber inevitably entailed an increase in the mass of the gun. For the infantry divisions, this was not critical (only more powerful tractors had to be introduced), but in the airborne units, the situation was different.
The lessons of the Arnhem operation, during which the British paratroopers had to fight German tanks, were taken into account by the American command. Since 1945, the US airborne divisions have received a 90-mm T8 anti-tank gun, which is a barrel of a 90-mm M1 anti-aircraft gun, combined with recoil devices of a 105-mm M2A1 howitzer and a lightweight gun carriage. The result was a gun weighing 3540 kg, suitable for parachute landing from C-82 "Pekit" aircraft, but problems began on the ground: the crew could not move such a heavy system across the battlefield. A tractor was required, which means that the number of flights of military transport aircraft required for the transfer of an anti-tank battery (battalion) doubled.
The solution could be the creation of a compact self-propelled anti-tank gun mount. For the first time, such an idea was expressed in October 1948 at a conference in Fort Monroe, dedicated to the prospects for the development of anti-tank weapons, and in April of the following year, the customer presented the tactical and technical requirements. Chief among them was the mass, which should not have exceeded 16,000 pounds (7260 kg) - the carrying capacity of the Paekit and the heavy landing glider, which was being developed at that time (but never put into service).
The development of the airborne tank destroyer was entrusted to the Cadillac Motor Car company, which was part of the General Motors concern. The chassis design was based on the solutions tested on the M76 Otter amphibious tracked transporter. Due to the limited dimensions of the aircraft's cargo compartment, the self-propelled gun could not be equipped with a wheelhouse, not to mention the roof - we had to confine ourselves to a small gun shield. The latter was intended to protect the crew from powder gases when fired, but not to protect against bullets or shrapnel.
The prototype, indexed T101, was ready in 1953. Two years later, the vehicle successfully passed military trials at Fort Knox, and was accepted into service under the designation M56 Gun Self-Propelled Anti-Tank - "M56 self-propelled anti-tank gun." The widely used name "Scorpion" was approved in 1957, the unofficial name "Spat" (from the abbreviation SPAT - Self-Propelled Anti-Tank) was less common. Serial production of the M56 lasted from December 1957 to June 1958, its volume was 160 units.
Design
The M56 self-propelled gun is an unarmored small tracked combat vehicle adapted for parachute landing from the C-123 Provider and C-119 Flying Boxcar aircraft (and, of course, from heavier military transport aircraft) and transportation by helicopters on an external sling. The body of the vehicle is welded aluminum, the crew consists of four people.
Engine-transmission compartment with a six-cylinder opposed four-stroke air-cooled carburetor engine "Continental" AOI-402-5 with a capacity of 165 hp. with. and a manual transmission "Allison" CD-150-4 (two gears forward and one reverse) is located in the front of the M56 body. The rest of the space is occupied by the fighting compartment, combined with the control compartment. In the center of it, a 90-mm M54 cannon is mounted on an M88 pedestal gun carriage. To the left of the gun is the driver's workplace (for him, the gun shield has a glazed window with a windscreen wiper), to the right is the gunner's seat. The commander is located behind the driver, the loader is behind the gunner. In the rear of the vehicle there is an ammunition rack for 29 unitary rounds. For the convenience of the loader, there is a folding step behind the ammunition rack.
The chassis of the self-propelled gun consists (in relation to one side) of four large-diameter road wheels with torsion bar suspension, equipped with pneumatic tires. Tires have special tabs that allow, in the event of a breakdown, to drive up to 24 km (15 miles) at a speed of up to 24 km / h. The drive wheel is front. Caterpillars are rubber-metal, 510 mm wide. Each track consists of two belts made of rubberized fabric and reinforced with steel cables. The belts are interconnected by stamped steel crossbars with rubber cushions. The ground pressure of the "Scorpion" is only 0.29 kg / cm2 (for comparison: for the M47 and M48 tanks this figure is 1.03 and 0.79 kg / cm2, respectively), which ensures good cross-country ability of the vehicle.
Installed on the "Scorpion" 90-mm gun M54 (barrel length - 50 calibers) was developed on the basis of the M36 gun used on M47 tanks. Compared to the prototype, it is lighter by 95 kg. The range of guidance angles in the vertical plane is from −10 ° to + 15 °, in the horizontal plane - 30 ° to the right and to the left. The barrel of the gun is a monoblock with a screw-on breech and a single-section muzzle brake. The shutter is wedge, semi-automatic, vertical. On top of the breech of the gun, two cylinders of hydraulic recoil devices are mounted. Gun guidance mechanisms have manual drives, manual loading. The gun is equipped with a telescopic sight М186 with variable magnification (4-8x).
The range of used ammunition is wide enough and includes all types of unitary rounds for tank guns M36 and M41; the use of 90-mm shells of anti-tank guns of the German company "Rheinmetall" is also allowed. For the solution of the main task - the fight against tanks - can be used: armor-piercing tracer projectile M82 with an armor-piercing tip and an explosive charge; armor-piercing tracer shells M318 (T33E7), M318A1 and M318A1C without explosive charge; subcaliber armor-piercing tracer shells M304, M332 and M332A1; cumulative non-rotating (feathered) shells M348 (T108E40), M348A1 (T108E46) and M431 (T300E5). In addition, the self-propelled guns can fire the M71 high-explosive fragmentation projectile, the M91 fragmentation-tracer, the M336 canister, the M377 fragmentation (with arrow-shaped striking elements) and the M313 smoke.
The vehicle is equipped with an AN / VRC-10 VHF radio station, which is maintained by the commander. The means of night observation are represented only by a helmet-mounted night vision device of the driver.
On the basis of the M56, two experienced self-propelled guns were created. In 1958, an anti-tank self-propelled gun was tested at Fort Benning, on which instead of a 90-mm gun, a 106, 7-mm M40 recoilless recoilless mechanism was installed - a regular jeep could easily cope with the transportation of such weapons, so it was not accepted into service. Another self-propelled gun, also not included in the series, was armed with a 106, 7-mm M30 mortar. On paper, there were also options for re-equipping the M56 with SS-10 and Entak anti-tank guided missiles.
Service and combat use
According to initial plans, each of the three American airborne divisions (11th, 82nd and 101st) was to receive a battalion of "Scorpions" (53 vehicles in each). But the adoption of the M56 into service coincided with the reorganization of the infantry and airborne divisions - transferring them from the usual "ternary" to "pentomic" structure. Now the division included not three regiments, but five battle groups - in fact, reinforced infantry (airborne) battalions. As a result, the "Scorpions" entered service with anti-tank platoons that were part of the command company of the airborne combat groups (VDBG). Such a platoon included control (platoon commander (lieutenant), his deputy (sergeant) and a radio operator with a jeep equipped with an AN / VRC-18 radio station) and 3 firing sections (each with 8 people and 2 self-propelled M56 self-propelled guns). Thus, the platoon consisted of 27 personnel, 6 Scorpions and 1 jeep.
In the first half of 1958, Scorpion platoons were formed in fifteen airborne combat groups - five in each division. However, already in July 1958, the 11th Airborne Division was disbanded - two of the Airborne Forces from its composition, along with the regular M56, were transferred to the 24th Infantry Division, but in January 1959 they were transferred to the subordination of the 82nd Airborne Division. The latter transferred two of its VDBG to the 8th Infantry Division. Finally, in June 1960, one battle group from the 82nd Airborne Division was transferred to the 25th Infantry Division, and one of the Airborne Forces, disbanded in 1958, was restored to supplement the 82nd Division. A number of Scorpions, which turned out to be redundant for the airborne battle groups, entered the infantry battle groups of the 1st Infantry Division in Germany, and the 1st Cavalry and 7th Infantry Divisions in the Republic of Korea.
In 1961, the "pentomical" structure was declared untenable and unsuitable for warfare in non-nuclear conflicts, and the US Army began another reorganization. In accordance with it, the airborne division included three brigade headquarters and nine airborne battalions, as well as support units, including a tank battalion. It was assumed that he would receive new M551 Sheridan airborne tanks, but as a temporary measure (before the Sheridans entered service) tank battalions of the 82nd and 101st Airborne Forces were transferred in 1964 to 47 Scorpions - vehicles, not not only tanks, but also not having any armor. No funds were allocated for the maintenance of the crews of these vehicles, so until the receipt of the Sheridans, these battalions remained “virtual”.
Company D of the 16th Tank Regiment (D-16), which was formed in 1963 as part of the 173rd Separate Airborne Brigade (VDBr) deployed on the island of Okinawa, became the only armored unit that operated and fought on the Scorpions. The company consisted of four platoons of four M56, a control section (four M113 armored personnel carriers) and a mortar section (three 106, 7-mm self-propelled mortars M106 on the M113 chassis).
In May 1965, the 173rd Airborne Brigade was transferred to Vietnam. During the war in the jungle, the strengths and weaknesses of the M56 were clearly manifested. On the one hand, the self-propelled gun's good maneuverability made it possible to move around "tank-inaccessible" terrain, on the other hand, there were few suitable targets for the 90-mm gun. The main task of the "Scorpions" was the direct support of the airborne battalions and companies operating on foot, and here the most serious drawback of the M56 was extremely acute - the complete lack of booking. The drop that overflowed the patience of the paratroopers was the events of March 4, 1968, when in one battle the company lost 8 people. After that, the "tankers" from the D-16 changed their M56 to more versatile and much better protected M113 armored personnel carriers.
After the American army was removed from service, some of the M56 self-propelled guns went to warehouses, some were transferred to the allies. Spain received five vehicles in 1965 - until 1970 they served in the anti-tank platoon of the Marine Corps regiment. Neighboring Morocco in 1966-1967 handed over 87 "Scorpions". According to the Janes World Armies directory, in 2010 the Moroccan army had 28 M56 self-propelled guns in storage.
In 1960, two prototypes of the T101, modified to the M56 serial standard, were transferred to the Federal Republic of Germany. The Germans were not tempted by the unarmored vehicle and did not accept it into service. After short trials, both examples were converted into training vehicles for the training of driver mechanics, removing the cannons and installing glazed cabins.
A number of decommissioned M56s were acquired by the American fleet. The vehicles were converted into QM-56 radio-controlled targets and in 1966-1970 were used at Fallon, Warren Grove and Cherry Point training grounds for combat training of attack aircraft pilots and fighter-bombers.
Overall score
The M56 self-propelled gun had good mobility and powerful weapons for its time. The cumulative shells of its 90-mm cannon could confidently hit any Soviet tanks of the first half of the 1960s. At the same time, the cannon was too powerful for a seven-ton chassis, the front rollers of which were lifted off the ground when fired. In addition, the absence of any booking allowed the use of self-propelled guns against tanks only in defense (from ambushes), making the "Scorpion" unsuitable for supporting the landing force in offensive operations.
Compared to its Soviet counterpart, the ASU-57 airborne self-propelled gun, the M56 is more than twice as heavy (7.44 tons versus 3.35 tons). In addition, the ASU-57 is more compact than its counterpart (its height is only 1.46 m versus 2 m) and, unlike the Scorpion, it has front and side armoring - however, its thickness (4-6 mm) is short distance did not even provide protection against conventional 7.62 mm bullets. As for the weapons, the superiority of the M56 was overwhelming: the muzzle energy of its 90-mm M54 cannon was 4.57 MJ, and the 57-mm Ch-51 cannon installed on the ASU-57 was only 1.46 MJ. In terms of mobility parameters (speed and power reserve), both self-propelled guns were approximately equal.
