Military Review

XM124 self-propelled gun (US)

In order to successfully complete the task and not be hit by the enemy, the artillery must be highly mobile. The obvious solution to this problem is to install the gun on a self-propelled chassis, but such a combat vehicle is complex and expensive. A simpler and cheaper option to increase mobility is to create a self-propelled gun. In the early sixties in the United States at the ground came the self-propelled howitzer XM124.

By the beginning of the sixties, the American command had time to learn about the Soviet projects in the field of self-propelled guns. Such weapons, capable of moving around the battlefield without a tractor and the assistance of the calculation, were intended for the amphibious units and seriously increased their combat potential. Albeit, with the most serious delay, the US Army became interested in this concept, as a result of which an order appeared to develop two new projects. With a successful completion, they could change the appearance of army artillery.

It should be noted that the US military did not want to directly copy foreign solutions. The Soviet SDO was a mobile anti-tank guns, and the US command considered it necessary to develop self-propelled howitzers. In this case, the development of two LMS with different calibers was ordered at once. The goal of the first project was the revision of the M114 howitzer of the 155 mm caliber, and the second was the mobile version of the M105A101 1-mm howitzer.

Howitzer M101A1 in the original configuration

Projects of a similar kind received corresponding designations. A more powerful self-propelled gun called XM123, and a system of smaller caliber - XM124. In both cases, the working names of the projects included the letter “X” indicating the status of the product, and in addition, they did not reflect the type of the base sample. In the future, new letters were added to the original notation, with the help of which the next modifications were highlighted.

The development of the DLS type XM124 was to be carried out by two organizations. Overall project management was carried out by the Rock Island Arsenal design department. He was responsible for the artillery part and the carriage. All new units had to create and deliver commercial company Sundstrand Aviation Corporation. At the same time, American Machine and Foundry, in collaboration with the Rock Island Arsenal, developed the XM123 howitzer. For obvious reasons, the creation of both howitzers did not trust one developer, and two private companies were involved in the SDS development program.

Two new models were created by different companies, but had to be built according to general principles. According to the technical task, the designers had to keep the maximum possible number of parts of the existing tool and gun carriage. It was necessary to create a set of components suitable for installation on a howitzer without significant modifications. The requirements also asked the approximate composition of the new units and their principles of action. It should be noted that the first versions of the two DLS did not suit the customer, as a result of which the projects were reworked. Modernization of two howitzers was also carried out using common ideas.

The project XM124 without major changes passed all the main units of the existing guns. Thus, the artillery unit was used in its original form, and the existing carriage with sliding beds was now completed with new devices. The wheel drive, which became the driving axle, was substantially redesigned with the introduction of new devices - including engines. According to the results of this refinement, the howitzer did not change its firing characteristics, but received mobility.

The M101A1 towed howitzer and its self-propelled modification were equipped with a 105 mm rifled barrel. The length of the barrel was 22 caliber. The barrel was not completed muzzle brake. In the breech, there was a chamber for a unitary shot and a semi-automatic horizontal wedge gate. The barrel was mounted on hydropneumatic recoil devices. Brake and nakatnik located under the barrel and above it. As part of the swinging part, a cradle was used with an elongated rear guide, necessary in connection with the rollback length of an 42 inch (slightly more than 1 m). On a cradle the manual drive of vertical laying was fixed.

The gun carriage was relatively simple. Its upper machine had a small size and was a U-shaped device with fixtures for the swinging part and for installation on the lower machine. There were also two side sectors for vertical guidance and one for horizontal.

The lower machine was built on the basis of a transverse beam with fastenings for all the necessary units, including the bed and the wheel travel. When creating the XM124 DLS, the design of the lower machine underwent some minor changes. First of all, engineers had to consider the possibility of installing new engines and gearboxes that provide wheel drive. All new devices are mounted on an existing beam.

The tool was completed with a pair of sliding beds of sufficient length and strength. Welded devices were hinged on the lower machine. To keep the gun in position in the back of the bed, openers were provided. As in the project XM123, one of the staninas was to be the basis for the installation of new units.

The M101A1 howitzer and its self-propelled variant received a composite-type shield shield. On the sides of the swinging part on the upper machine were fixed two plates of similar shapes and sizes. Two more protection elements were installed on the lower machine, directly above the wheels. They consisted of two parts: the top could be folded, improving visibility. Under the lower machine was another rectangular shield. In the fighting position, he went down and blocked the ground clearance, in the marching position - it was fixed horizontally, without interfering with the haulage.

The gun was equipped with sighting devices that ensured direct fire and from closed positions. Using hand drives, the gunner could move the barrel within the horizontal sector of width 46 ° and change the elevation from -5 ° to + 66 °.

XM124 self-propelled gun (US)
XM124 at the test site during sea trials

In the first version of the XM124 project, almost the same power plant was used as on the XM123 DLS. A tubular frame was placed on the left base of the gun, on which were all the necessary devices and the driver’s workplace. In addition, part of the new devices appeared on the front of the lower machine - near the wheel travel.

On the frame was placed a pair of gasoline air-cooled engines with an 20 horsepower. each. Probably, engines of Consolidated Diesel Corporation, similar to those used in the 155-mm DLS project, were used. In front of the engines there was a pair of hydraulic pumps, which created pressure in the mains and were responsible for the transmission of energy to the wheels. In the first versions of the XM123 and XM124 projects, a hydraulic transmission with a fairly simple design was used. Through the pipes, the liquid flowed to a pair of hydromotors installed on the carriage. Through compact gears they rotate the wheels. In fact, the implement had two separate hydraulic systems, one for each wheel. Hand-operated parking brakes are preserved on the wheels.

Right on the pump mounted seat for the driver. On the sides of it were two control levers. Each of them was responsible for the flow of fluid to its hydraulic motor. Their synchronous movement allowed to move forward or backward, while the differentiated movement ensured maneuvering. From the point of view of the controls, the XM124 DLS was a bit more convenient than the XM123, where all control was exercised by a single lever swinging in two planes.

Directly under the power unit on the bed, in front of the opener, a self-guiding wheel of small diameter was placed. When moving, it had to take on the weight of the beds and new units. The wheel rack had swiveling mounts, which made it possible to fold it when deployed to a position.

After the modernization, the overall dimensions of the gun remained the same. The length in the stowed position did not exceed 6 m, width - 2,2 m. The total height was slightly more than 1,7 m. In the basic version, the howitzer weighed 2,26 t; The new version of XM124 was noticeably heavier due to the special configuration. At the same time fire qualities should not be changed. The barrel length 22 caliber accelerated projectiles to speeds of the order of 470 m / s and provided firing at a distance of up to 11,3 km.

In the stowed position, the XM124 self-propelled howitzer rested on three wheels, two of which were driving. The ride was carried forward with the barrel, with the gun and the carriage limited visibility from the driver's seat. Upon arrival at the firing position, the calculation was to turn off the engines, activate the brakes of the main wheels, and then raise the beds and fold the rear wheel sideways. Further, the beds were divorced to the sides, the openers were sunk into the ground, and the howitzer could fire. Translation to the traveling position was carried out in reverse order.

Own power plant was designed to move between closely located firing positions. For long-haul transport, the XM124 needed a tractor. At the same time it was necessary to raise the rear wheel, which can interfere with normal hauling.

In the middle of 1962, the Rock Island arsenal and the company Sundstrand Aviation Corporation launched the first prototype of a promising weapon on the test site. In parallel, the 155-mm XM123 howitzer was tested on the same site. The system caliber 105 mm showed not too high, but acceptable mobility characteristics. Expected own speed was lower than with a towing vehicle. On the other hand, manually rolling the howitzer was even slower. However, the power plant and transmission needed improvement.

The fire tests of two LMS ended with similar results. In the combat position, the weight of the engines and hydraulic pump fell on the left frame, which disrupted the balancing of the gun. When fired, the howitzer was blown back and simultaneously turned in a horizontal plane. This fact seriously hampered the restoration of aiming after a shot and sharply reduced the practical rate of fire.

After testing, both guns went for revision. According to the results of the new design stage, the LMS XM124E1 and XM123A1 were derived at the polygon. In both cases, the new aggregates responsible for the movement underwent the most serious revision. From the base 105-mm howitzers removed one of the engines, as well as both pumps. Instead, they installed an electric generator and new traffic controls. The hydraulic motors on the bottom machine tool carriage were replaced by electric ones.

The only surviving sample of the XM124 DLS, allegedly related to the modification "E2"

A new version of the gun came to the test and showed its potential. The electric transmission was almost no different from the hydraulic one in its efficiency, although the new power plant had a noticeably lower weight. The rest of the two modifications of the CAO were similar. In this case, the refusal of the engine and pumps did not allow to get rid of the problem with the turn when shooting. The left frame still outweighed and led to undesirable movements.

There is information about the development of modifications XM124E2, but it raises serious questions and doubts. The gun of this type is in the exposition of the Rock Island Arsenal Museum. The information plate indicates that the presented product belongs to the E2 modification and is the third experienced instrument of the series. At the same time, in any other sources the LMS XM124E2 is mentioned only in the context of a museum exposition. In addition, the museum sample is equipped with a hydraulic transmission, which raises new questions.

It is quite possible that the very first modification of the XM124 self-propelled howitzer, assembled according to the initial project, stands on the museum site. As for the information plate, it may be erroneous. However, it cannot be excluded that the third modification of the LMS was nevertheless developed and had the maximum similarity with the basic one, but for some reason the full information about it did not become public.

According to different sources, in the early sixties, Rock Island Arsenal and Sundstrand Aviation Corporation built and tested up to three prototypes of two or three types. Serial howitzers, equipped with new devices, could independently move around the battlefield, but their mobility still left much to be desired. In addition, they had improper balancing, which led to an unacceptable displacement when shooting. In this form, the LMS XM124 and XM124E1 were not of interest to the army. By the middle of the decade, the customer ordered to stop work on unpromising projects.

One of the experienced XM124 later hit the Rock Island Arsenal Museum. The fate of others is unknown, but they could be returned to their original state or simply disassembled. The only known model of such weapons is now a mystery and leads to a certain confusion.

Projects of self-propelled guns XM123 and XM124 were based on common ideas and used similar units. As a result, real characteristics and capabilities, as well as drawbacks and problems, turned out to be the same. Both howitzers did not suit the army, and as a result they were abandoned. In addition, due to the failure of the first projects, work on all subjects of self-propelled guns stopped for several years. A new sample of this kind appeared only by the beginning of the seventies.

On the materials of the sites:
Photos used:
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  1. aristok
    aristok 30 September 2018 21: 07
    Maybe it made sense (and now too) to make a separate battlefield tractor?
    something like a small 6-wheeled all-terrain vehicle (dimension with an ATV).
    at the same time could solve other problems.
    And carry it over long distances with an ordinary tractor.
  2. hagrid
    hagrid 19 November 2018 02: 46
    today is November 19th! Happy holiday comrades !!!