When German forces swept through Europe, the US Army realized it needed better anti-tank weapons. One successful weapon combined two cutting-edge innovations:
An Ordnance Department civilian, Gregory J. Kessenich, tipped off the rocket section to the potential of a new type of explosives technology perfected by Swiss engineer Henri H. Mohaupt. In late 1940 Mohaupt had offered the U.S. Army a shaped-charge projectile. The hollow cone molded into the front of the explosive charge focused much of the blast into a hot jet that could burn a hole through armor. Unlike existing antitank rounds, which depended on speed and mass to create the energy to penetrate, Mohaupt’s shaped charge would work even when it made contact with the target at a relatively slow speed. Thus the warhead could be fired from smaller less powerful weapons, making it perfect for use by foot soldiers.
The Ordnance Department had acquired and tested Mohaupt’s 30-mm. shaped-charge rifle grenade and found it capable of penetrating 2 inches of hardened steel. Work frantically began on a 60-mm. design after the Army received a report from the British that the Germans were increasing the thickness of the armor plate on their panzers to 4 inches. Standardized as the M10 grenade, the 60-mm. version was up to the new challenge, but it had gained a major flaw. The charge required to launch this heavier projectile a sufficient distance produced a great deal more recoil. Because the butt of the M1 Garand rifle had to be placed on the ground to gain elevation and range, the wooden stock absorbed the shock and often broke in the process.
In a search for something capable of launching the M10, the Army turned to a concept dubbed the spigot mortar. This notional weapon was basically a solid rod with a trigger mechanism located at the base. The projectile consisted of the shaped-charge grenade attached to a length of hollow tube that fit down over the mortar’s rod. Pressing the trigger activated a firing pin located at the tip of the rod, which in turn ignited a propellant charge in the base of the grenade. The expanding gasses from the burning propellant thrust the projectile off the rod, with the tube imparting initial guidance. Similar to a traditional mortar, the recoil would be absorbed into the ground on which the weapon rested.
The advantages of the spigot mortar were several. It was small, light, easy to operate, simple to manufacture, and cheap. While the first three factors made it attractive to an infantryman, all of them were important to ordnance designers given that the Army wanted to field large numbers of the man-portable antitank system in a very short period of time. The only obvious drawback to the system was its relatively short range. The Ordnance Department asked several private firms to each develop a working spigot mortar capable of firing the 60-mm. shaped-charge grenade. The Army planned to test the prototypes in a competitive shoot off at Aberdeen in early summer 1942.
While others sought ways to effectively employ the 60-mm. grenade, Uhl focused on marrying the round to a rocket that would get it to the target. By February 1942 he had successfully assembled a prototype antitank rocket by adding propellant, a gas trap, an igniter, and stabilizing fins to an inert M10 grenade. Firing tests conducted at the end of the dock that projected into the Potomac revealed that the new design had the desired range and ballistic properties. The next step was to construct a portable launcher. The main component came from an unexpected source. While rummaging through the scrap pile behind his workshop, Uhl came upon a 5-foot length of metal pipe that proved just wide enough to accept a 60-mm. round. Upon inspecting Uhl’s discovery, Skinner remarked that he had a spare rifle stock at home that could be fitted to the underside of the tube. He also suggested Uhl add a pair of grips to make it even easier to handle. The pair decided to use a trigger-activated electric igniter that sent a charge through a wire to the base of the rocket. Once these features were added to the design, all that remained was to conduct a live-fire test to see if everything worked.
Uhl received the mission to fire the first rocket. Wearing a welder’s mask and gloves, he walked to the end of the pier. A small group of observers, including Skinner and Hickman, watched from the shore. After ensuring no watercraft were nearby, Uhl pointed the tube toward the middle of the river and pressed the trigger. When it fired, he heard only a whooshing noise and felt absolutely no recoil. He discovered that the rocket did not generate enough exhaust to justify wearing any protective equipment.
Based on this success, Uhl assembled enough inert rockets to conduct more extensive testing. Skinner decided that the combination of rocket and launcher should be tested at Aberdeen during the spigot mortar shoot off in May. On the morning of the scheduled test, Uhl and Skinner arrived at the range before anyone else. Spotting a tank in the impact area, Uhl walked over to talk to the driver who confirmed that his vehicle was indeed the target for the pending competition. The soldier also explained that he was to navigate a specific course, which he pointed out to Uhl, and that he was to do so at a speed of twenty-five miles per hour. Uhl paced off the distance back to the firing line. After scribbling some figures down on a matchbook, he concluded he had to aim one tank length in front of the vehicle and slightly above the top of the turret to obtain a hit on a moving target at that range.
The crews of the spigot mortars arrived and began assembling their weapons. Uhl and Skinner occupied a sixth firing point about fifty yards to one side. A group from Army Ground Forces headquarters, headed by a lieutenant general, appeared soon afterwards. The officers were accompanied by Brig. Gen. Gladeon M. Barnes, head of the Ordnance Department Research and Development Section. The test began with a signal from Barnes to the tank crew. As the vehicle moved back and forth, the spigot mortars took turns firing dummy rounds at the target. It quickly became apparent that the high trajectory of the projectiles — required for maximizing range, given the low propellant charge — made the weapon highly inaccurate, especially against a moving target. Each mortar missed when its turn came, producing audible groans from onlookers.
Just before the competition began, Uhl and Skinner had realized their rocket launcher lacked a sighting mechanism. Uhl extracted a wire coat hangar and pliers from the trunk of his automobile. The young lieutenant constructed a front sight, featuring an upright blade, and a circular rear sight, in which the firer centered the front blade. Using a telephone pole as a reference point, Skinner looked down the length of the empty firing tube to ensure it remained centered on the pole as Uhl bent two sections of a coat hanger around the tube. This final modification to the launcher was completed before the spigot mortars had finished firing.
After the fifth prototype missed, Uhl took aim at the moving tank and pulled the trigger. A rocket whooshed downrange to score a direct hit. The officers sitting on the bleachers cheered and threw their hats in the air. The Army Ground Forces three-star approached Skinner to ask if he could test fire the launcher. Uhl relinquished it to the general, explaining the trigger mechanism and sighting procedures as the senior officer prepared to fire at the tank. The general scored a direct hit. Barnes now took a turn and was also successful. Others test fired the weapon with only one rocket missing the target.
When all the projectiles were expended, Barnes stepped forward once more to closely examine the launch tube. He casually remarked to Skinner: “This sure looks just like Bob Burns’ bazooka.” Burns was a famous radio comedian whose publicity photos often depicted him playing a cobbled-together musical instrument he called “The Bazooka.” Although the Army would formally designate the weapon the 2.36-inch rocket launcher M1, the nickname coined by Barnes would stick.