The ‘Slammer’ Turned Aircraft Rockets Into Ground-Based Artillery
U.S. Army project aimed to give paratroopers extra firepower
by JOSEPH TREVITHICK
As conflicts in the Middle East and North Africa rage on, pictures pop up on social media of all sorts of unusual, locally-built military vehicles, often based on civilian trucks. Usually lacking the pilots to fly captured fighter-bombers or gunship helicopters, militants and rebels have strapped aircraft rocket pods onto pickups, jeeps or trailers.
While these home-brew weapons are the product of necessity, during the Cold War the U.S. Army built and tested prototypes of a similar weapon. The ground combat branch thought the repurposed rockets could give paratroopers and other light troops some extra firepower.
“Even though multiple rocket launchers, with their unguided, free-flight rockets have been described by some as primitive, they can do wonders,” Army Capt. Charles Brenner wrote in defense of the Slammer in the September-October 1985 edition of Field Artillery Journal. “In fact, the U.S. needs such weaponry now!”
The Army’s leadership agreed with Brenner’s argument, but not necessarily in the way he might have hoped.
At the end of World War II, the Army had fully embraced the idea of rocket artillery. The ground combat branch’s weaponeers devised launchers for jeeps, cargo trucks and tanks.
But with atomic war on the horizon, the service and its cousins increasingly felt conventional weapons would not be enough to hold back Soviet troops on the battlefield. American troops steadily got nuclear-tipped rockets, missiles and more.
By 1960, Army engineers had craft just one new rocket launcher for soldiers on the ground. However, the ground combat branch only expected the M-91 to hurl 115-millimeter projectiles filled with poison chemicals — first Sarin and later the more potent VX nerve gas.
While Viet Cong guerrillas and North Vietnamese troops regularly lobbed Soviet and Chinese rockets at their opponents, American troops had no large rocket weapons to speak of during the Vietnam War. After that conflict ended, the Army finally decided to invest in a new artillery launcher.
Still, the ground combat branch envisioned a large weapon firing big projectiles to smash Soviet tanks and armored vehicles. The proposed tracked vehicle would be too big for U.S. Air Force cargo planes to drop with paratroopers or for other lightly-equipped troops to bring into battle.
Enter the “Slammer.”
In 1975, soldiers from the 4th Battalion, 77th Field Artillery Regiment, part of the 101st Airborne Division, built the first prototype launcher. The year before, the Army had transformed the 101st into an air assault unit specializing in helicopter assaults rather than air drops.
Though no longer planning to jump out of airplanes, the troops understood the need for weapons that packed a punch, but were easy to move. Also known as the XM-477 after the battalion, the first iteration of the Slammer combined six M-200 aircraft rocket pods with an old trailer.
Designed for the Army’s gunship choppers, each pod held a total of 19 2.75-inch rockets. When fully loaded, the whole rig could fire more than 100 of these small, unguided projectiles.
Soldiers would aim the cart with a sight taken off an 81-millimeter mortar. The artillery troops modified the rocket firing gear from an AH-1 Cobra attack helicopter into a handheld trigger powered by two 12-volt batteries. It took only 30 seconds to launch a full salvo.
In the first test in October 1975, “the Slammer provided target coverage of an area approximately 150 by 250 meters,” Capt. R. F. Parker, Jr. of the 101st explained in an article in Field Artillery Journal nearly two years later. “This system is easily transportable, is highly mobile, and can fire further rocket loads from subsequent locations.”
On top of that, by using the aircraft rockets, troops already had a wide array of projectiles to choose from, Parker added. The U.S. Navy and Air Force both turned the 2.75-inch projectiles — originally designed in the 1940s to shoot down enemy bombers — into ground-attack weapons.
By the 1960s, the sailing branch had built an improved, common rocket motor. Armorers could then screw in different warheads to make up complete rounds.
Troops with a Slammer could lob rockets full of high explosives, white phosphorus, flares and more at their enemies. Any new aircraft versions — including warheads full of small darts called flechettes or even tiny grenades — could be quickly adapted for use on the ground.
The 101st built at least six different iterations of the Slammer for tests. One variant featured two M-200s on the back of an M-151 jeep. The troops also suggested putting the full, six-pod arrangement on the back of a larger six-wheeled cargo truck.
In November 1976, the division brought the trailer-mounted launchers out for a large war game with other Army units and members of the Air Force and U.S. Marine Corps. The system worked, but the Army wasn’t particularly enthusiastic.
“Slammer performed adequately as an area fire weapon, placing a high volume of fire on the target with acceptable accuracy,” was the milquetoast description that Army Majors Thomas Gaither and Bobby Getz gave as part of a larger report on the practice session for Field Artillery Journal the following year. The officers didn’t say whether anyone was overly impressed or interested in the system.
By the time Brenner made his case nearly a decade later, the Slammer was already fading from memory. The Army had focused its energy on the large, tank-busting launcher, eventually dubbed the M-270 Multiple Launch Rocket System.
Able to lob a dozen 227-millimeter rockets packed with hundreds of small bomblets at enemy troops more than 40 miles away, the M-270 was decidedly more powerful than the Slammer. By 1992, the same launcher could fire two GPS-guided missiles at targets more than four times further.
Six years later, the ground combat branch began testing a precision guided version of the smaller projectiles. But the heavy launcher remained a problem for many units, especially those operating in remote areas.
In 1998, the Army began testing a smaller and lighter six-tube version on a standard truck chassis. In service for more than a decade, the ground combat branch and the Marine Corps sent these wheeled launchers to fight in Afghanistan and Iraq.
In 2015, American troops started pounding Islamic State terrorists in Iraq and with these deadly weapons. Though these new launchers are still much larger than the Slammer, the Army has left the idea reusing aircraft rockets as artillery on the ground to militants.