Official Caption: Ready for Firing – The 30-foot tube of the 175mm gun points the direction. Its 150-pound projectile will travel up to 20 miles. Date: 1969.
That year, the Marine Corps retired the aging M53 gun and converted all the 155mm Fires batteries to 175mm Gun Batteries after the 12th Marines had enjoyed the support of Army 175s in Vietnam in 1967-68.
The M107 175 mm self-propelled gun was a 28-ton beast that could move over roads at up to 50mph (in theory) and was able to hurtle 147-pound shells to 25 miles, far outclassing 155mm and 105mm pieces and rivaling the impractically large 203mm guns and naval gunfire support from 6- and 8-inch guns on cruisers and 5-inch guns from destroyers/frigates.
The guns could lay lots of warheads on foreheads so to speak. In 1968’s six-day Operation Thor, Marine artillery averaged 4,000 rounds per day into the target area from 155, 175, and 203mm guns, in addition to 3,300 daily naval gunfire support shells and 2,400 tons of ordnance dropped by aircraft every 24 hours.
Post-Vietnam, the Army updated their remaining M107s to 8-inch guns for use in Europe for another decade along the Fulda Gap, dubbing the new vehicle M110A2s, while the Marines went back to lighter, towed 155mm guns.
Other than use by the IDF against various neighbors and by the Iranians against the Iraqis in the 1980s, the only combat saw by the M107 was by the Army and Marines in Vietnam– where several captured in 1975 are still in arsenal storage.