Great guns: M7 'Priest' backs WWII armor
September 29, 2011
FORT SILL, Okla. -- The second part of the series 100 years of artillery looks at the M7 Priest, a self-propelled howitzer that saw extensive use during World War II as the primary artillery support for armored divisions.
The gun got its nickname from the British who said the .50 caliber machine gun ring mount looked like a European church pulpit.
Following World War I, U.S. artillery was seen to be unsatisfactory for modern warfare. Hence, the Army chief of staff set up the Westervelt Board in 1919 which studied existing artillery of British, French, Italian and German designs. The board came up with four important conclusions. Board members said field artillery needed to be:
- motor towed;
- able to elevate up to 75 degrees elevation to drop shells into enemy trenches or ammunition dumps on the reverse sides of slopes; and
- capable of 360 degrees traverse.
"A lot of this was generated by the idea that in the future, battles would move faster because of motor vehicles, and with greater traverse, artillery could keep up with the speed of the battle," said Dr. Boyd Dastrup, Fort Sill field artillery historian.
These modifications would improve significantly on existing artillery, such as the 75 mm French gun, that was horse drawn and required additional horses to haul ammunition and spare parts. Also, artillery had to be unlimbered, moved into place and aimed prior to firing.
He said in the early 1930s Army leadership and the Field Artillery School remained leery of motorized artillery.
"What the Army had then was senior field artillery officers who were born and raised in the horse-and-buggy era. They were familiar with that, and asking them to go from a horse as a piece of technology to motor vehicles was a huge leap forward," said Dastrup, who added people then viewed vehicles as smelly and unreliable.
He said towed artillery gained more acceptance initially, because artillery still arrived at a firing location pulled into place not unlike cannons drawn by horses. Still, towed artillery still necessitated unlimbering, aligning the gun to the target and firing. Also, ammunition wasn't hauled on the weapon.
Military budgets certainly factored in the development of vehicles. With the end of the war, defense spending diminished. Given this fiscal shift, one vehicle could replace a team of six horses to pull an artillery piece not to mention additional horses needed to haul ammunition and spare parts. Also, once artillery was in place, horses still needed to be fed, whereas vehicles could be shut off with no "feeding" required until it moved again.
As the world moved into WWII, self-propelled artillery began to gain acceptance. Speed was of the essence, and a self-propelled gun could be placed and engage the enemy much quicker. Conversely, if need be it could also disengage rapidly and retreat to safer terrain. Either way, self-propelled weapons systems could move more rapidly over rugged terrain and keep up with armor.
Development began on the M7 Priest in June, 1941 still six months prior to the United States officially entering the war. The first vehicle entered service in the spring of 1942 in the role of providing indirect fire artillery support to armored divisions.
It employed a crew of seven: a commander, driver, gunner and four Soldiers to handle ammunition. The 50,000-pound self-propelled howitzer could hit 26 mph on a road or 15 mph cross-country. Fuel efficiency was about 0.67 miles per gallon.
One significant improvement over towed artillery was the Priest's capability to haul its own ammo. Firing a 105 mm cannon with a range of more than 10,400 meters, the Priest could carry 69 shells.
Some Priests were converted either to carry a radio, which cut 24 rounds of ammunition, or troop carriers capable of hauling 20 Soldiers plus a commander and driver. The vehicle also had a .50 caliber machine gun.
Like the Priest on display at the Field Artillery Museum at Fort Sill most did not provide the crew any protection from the elements. Dastrup said some had a canvas cover that could be erected to give some relief from snow or rain.
Although the Priest was used for indirect fire, its maximum elevation to raise the gun barrel only reached 35 degrees. This required crews to position the weapon on inclines to achieve greater elevation to lob shells into enemy positions.
The Army normally used four self-propelled Priests per battery, with three firing batteries per battalion. Each gun fired a 100-pound shell either a high explosive steel shell, smoke or illumination rounds.
The fires direction center would then call for mass fires all aimed on a particular target. This was termed "area destruction," and the circular error of probability was quite large. Any shell that exploded within a given range was acceptable to ensure taking out a specific target.
About 4,200 Priests were built, and production ended in 1945. The weapons system continued to see action in the Korean War.
The series moves on to the turbulent 1960s catching a glimpse into the early years of escalated American involvement in the Vietnam War. Aerial rocket artillery, a precursor of the AH-64 Apache, was first tested in 1964 at Fort Sill and was frequently used throughout that war. Though effective, the technology was developed for a far different purpose.