Recoilless rifles, commonly referred to as RRs or RCLs, are tube-fired guns that unleashed a heavy shell with supremely high power. These guns, arrived late to the World War II scene, first utilized in ground combat around February of 1945, just three months before the German army surrendered to the Soviets in Berlin and six months before the U.S. dropped atomic bombs on Hiroshima and Nagasaki. Although the RCL was a late arrival for WWII, it became a bastion for the American soldiers during the Korean War.
The Facts
The RCLs were much lighter than prior tube-fired guns, allowing for more maneuverability and mounting options, but a shorter useful range. The first of these guns was the M20 75mm, which was used as an alternative to the 3.5” bazooka as an anti-tank/anti-personnel weapon. The M20 initially had 1,000 feet per second muzzle velocity. These guns were vented at the rear with propellant gas that eliminated much of the recoil and used a pre-engraved shell, which encouraged the round to spin as it was forced through the barrel. Later models of 75mm would have velocities of over 2,000 fps. Around 1950, the M20 was traded out for the M27 105mm RCL that was heavier and more powerful.
M20 75mm RCL vs. M27 105mm RCL
● 114 lbs / 365 lbs.
● Projectile Weight: 20-22 lbs / 50 lbs.
● Rate of Fire: 8 rpm /10 rpm (rounds per minute)
● Range: 3.9 mi (6,864 yds.) / 4.8 mi. (8,500 yds.)
Mounting Options & Challenges
The M18 57mm RCL that preceded the M20s and M27s were powerful shoulder-mounted guns; however, the increase in weight and power, especially for the latter RCL, required mounting via .30 cal. machine gun tripod or a Jeep.
The length of the recoilless rifle was a particular challenge for Jeep mounts. The nearly-7-foot-long RCL took up over 60% of a Jeep’s standard length (roughly 11 ft. for the Willys MB). As a result, various Jeep alterations were designed to accommodate the RCLs inconvenient length and the terrible rear blast, the area of which extended 100 ft. to the rear and 20 ft. to the sides of the vehicle. Windshields, in general, were a hindrance to recoilless rifles and were sometimes left off Jeeps entirely, making inclement weather, mud, and dust difficult to cope with. Some other modifications included:
● The forward-mounted RCL designed by Lieutenant Fred Dawson, platoon leader in Company H, 18th Infantry Division, around 1951
● Dual-mounted guns on both rear corners
● Exclusion of windshield
● Modified windshield with an offset slot for the barrel
For over a decade, recoilless rifles were mainstays in U.S. military endeavors until the introduction of wire-guided missiles in the 60s and 70s during the Vietnam War. Although the remaining RCLs were not used in a military context, they were not necessarily phased out of use until the stockpiles of rounds were used up in the 1990s by the National Forest Service and the National Park Service, which used RCLs as controlled avalanche starters.
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