Production cost and time are drastically lower than for standard cannon or other small-arm weapon systems firing a projectile of the same size and weight.

Large anti-tank cannon firing high velocity projectiles were the best option, but costly to produce and required a well trained crew.

[2] In 1944, the German firm Rheinmetall–Borsig came up with a completely new concept for propelling a projectile from a cannon, which, while not recoilless, greatly diminished recoil and drastically reduced the manufacturing cost.

Unlike high-velocity armour piercing ammunition, which has a heavy steel case, the shaped charge had only thin metal wall, reducing the weight of the shell body and increasing the explosive payload.

A round steel plate with eight holes in it was fitted at the mouth of a cut-down cannon shell casing which contained two propellant bags.

[3][4][5][6] The only major drawback was its maximum range of 750 meters (in direct fire against tanks), but this was offset by an armor penetration of 140 mm and no telltale back-blast.

The first example of a type of high-low system developed after World War II was the British Limbo antisubmarine weapon, which launched depth charge-like projectiles.

[12] Later, the U.S. Army developed a higher-velocity 40 mm round using their high-low propulsion system for use by heavier machine gun-type grenade launchers found on vehicles and helicopters.

[13] Shortly after the Vietnam War ended, the Soviet Union introduced a 40 mm grenade launcher that used the high-low principle, but with a twist on the original design.

While little documentation exists, in the 1950s the Soviet Army developed a 73 mm cannon for wheeled armored reconnaissance vehicles that fired a munition very similar in operation to the original World War II German concept.

However, it was never introduced into service, and instead the Soviets developed a 2A28 Grom low velocity 73 mm cannon that fired a rocket projectile which was ejected by a small charge in the normal fashion.

Unlike other high-low systems, gases are allowed to escape to the rear of the launch tube, causing a fully recoilless effect.