Developed alongside the storied M110 Self-Propelled Howitzer was the M107. Both vehicles utilized the same five road-wheeled chassis and general arrangement of components. Differences lay in the choice ofarmament - the M107 fielding the 175mm long-barreled howitzer and the M110 given a short-barreled 203mm type. The vehicles shared a Detroit Diesel Model 8V71T 8-cylinder turbocharged diesel and all aspects of its running gear were equal. The engine drove the drive sprocket at the front of the vehicle and was, itself, mounted forwards (front-right) to allow the gun and applicable mounting hardware to be mounted over the rear. The powerpack was mated to an Allison XTG041102A cross-drive transmission system and suspension of a torsion bar design. Like the M110, the M107 required a five man standard crew with the gunnery section operating in the open-air portion of the upper hull. The driver resided in the hull at front-left.
The M107 joined the M110 as all-new self-propelled artillery developments intended to supersede aged, outmoded and retired vehicles of similar mission scope. The U.S. Army laid down the requirement a replacement and these would have to be further air-transportable across the several Army transports then in use. Pacific Car and Foundry returned with the two SPA designs in pilot vehicle form - the M107 and M110. Utilizing the same chassis allowed the vehicles to be interchangeable with parts, proving logistically sound. Repairs and availability of spare parts would also be helped.
Pacific Car delivered its first M107s during 1962. The 31-ton system mounted the M113 gun of 175mm caliber. The mounting hardware allowed for an elevation range of +65 to -5 degrees with traversal from the rotating platform reaching 30-degrees to left and right from center. Maximum range was 25 miles thanks to the long barrel in use. While a crew of five was standard, a support staff of eight followed in an M548 carrier vehicle along with the 175mm ammunition. When the M107 was readied to fire, a spade was lowered at the rear of the hull to brace the system for the recoil effect.
Dimensions included a length of 21 feet, 2 inches, a height of 11 feet, 5 inches and a width of 10 feet, 4 inches. Road speeds reached 50 miles per hour on roads and the vehicle ranged out to 450 miles on internal fuel.
The M107 was adopted in time to see combat service with American forces during the Vietnam War (1955-1975). The long-barrel gun tube gave good service when attempting to hit enemy forces at range and without visual sighting being attained. The barrel caused excessive overhang over the front hull of the vehicle which proved problematic in transporting actions. To help facilitate this, the gun was retracted some rearwards to lessen the overhang but it was still an issue. Regardless, its capabilities were such that the M107 fired a 175lb projectile against target areas miles away, providing a distinct reach for any commander requiring suppression or disruption of enemy forces at range. Compared to the M110, which was in production and service at the same time, the M107 outranged it but lacked its 203mm firepower and overall accuracy. The M110 eventually supplanted the M107 with both the U.S. Army and USMC during the late 1970s. Due to the same automotive components shared between the two designs, many viable M107s were simply converted to M110s instead of scrapped.
Additional M107 manufacturing was undertaken by FMC Corporation and Bowen-McLaughlin-York. Operators beyond the United States became West Germany, Greece, Iran, Israel, Italy, South Korea, Turkey, Spain, the United Kingdom, and North Vietnam/Vietnam. The NVA captured existing examples during its conquest of the South. These are still held in reserve status by its modern army force. The Israelis used the M107 (as the "Romach") during its Yom Kippur War (1973) against Egyptian and Syrian forces. Greek forms have been converted to the M110A2 standard as have Spanish Army versions.