The solution was to replace the underwing gun pods, and the excessively drag-producing large-calibre underwing rocket launch tubes, with a small-diameter solid-fuel rocket-engine-propelled projectile, mounting a warhead similar to that of the cannon shell. Although each "round" was heavier than the corresponding gun-fired shell, the absence of a gun reduced the overall weight considerably. The weight difference was so great that even a much larger and longer-ranged rocket was still lighter than the guns it could replace.
The anti-aircraft version of the R4M used a large warhead of 55 mm with 520 g. (17.6 ounces) of the strongly
brisant Hexogen explosive charge, nearly guaranteeing a fighter kill with one hit, from the "shattering" force of its explosive warhead — this was the same explosive used in the shells fired by both the MK 103 (30 x 184mm cartridge) and MK 108 (30 x 90mm cartridge) autocannons. Each R4M weighed 3.2 kg and was provided with enough fuel to be fired from 1000 m, just outside the range of the bomber's defensive guns. The main body of the rocket consisted of a simple steel tube with eight base-hinged flip-out fins on the tail for stabilisation, deployed immediately after launch. A battery typically consisted of two groups of 12 rockets and when all 24 were salvoed in an attack, they would fill an area about 15 by 30 m at 1000 m, a density that made it almost certain that the target would be hit. The R4Ms were usually fired in four salvos of six missiles at intervals of 70 milliseconds from a range of 600 m, and would supersonically streak towards their target at a sixty percent higher velocity than the
Wfr. Gr. 21's rockets would (the BR 21's projectile traveled at some 715 mph post-launch), as the R4M typically had a flight speed of roughly 1,890 km/h (1,175 mph). Two warheads were available for the R4M, the common
PB-3 with a 0.4 kg charge for
anti-aircraft use and the larger shaped charge, similar in construction to the
Panzerschreck, the
Panzerblitz II/III (PB-2/3), for
anti-tank use. The
Panzerblitz III, mounting a gigantic 210 mm
hollow charge warhead (the same calibre as the BR 21), can be seen as the ultimate development of the basic
Orkan rocket. It was intended to be carried (six or eight rockets per plane) by the
tank-busting B model of the
Henschel Hs 132 jet
dive-bomber - however, neither the missile nor the warplane it was exclusively intended for got beyond the prototype stage before the end of the war.
Only a small number of aircraft were fitted with the R4M, mostly
Messerschmitt Me 262s and the ground attack version of the
Fw 190s, which mounted them on small wooden racks under the wings.
The Luftwaffe found the R4M missiles to have a similar trajectory to the 30 mm
MK 108 cannon's rounds in flight, so the standard Revi 16
B gunsight could be utilized