The Wfr. Gr. 21's projectile had a velocity of per second (1,150 km/h, 716 mph) and a maximum range of . The rocket and tube weighed some in total. A time fuse detonated the warhead at a pre-set distance of to from launch point, resulting in a lethal blast area approximately wide. Single seat fighters carried a single tubular launcher under each wing, while the "Zerstörer" heavy twin engine fighters carried two under each wing. Operationally the weapon had several disadvantages; the launcher tubes produced significant air resistance, as well as reduced speed, maneuverability and general performance. Unlike the firmly attached underwing conformal gun pods carried by many Luftwaffe anti-bomber single-engined fighters, the BR 21's tube launchers were jettisonable, and once the rocket had been fired the fighter could revert to a 'clean' profile. The relatively low velocity of the rocket created a considerable problem in attempting to counter the resultant ballistic drop of such a slow-moving projectile, which required that the launcher tubes be mounted at a roughly 15° angle upwards from the line of flight, causing considerable drag on the airframe of the carrier aircraft. The low launch velocity and the high angle at which the rocket was launched meant that both accurate aiming and correct judgment of the target's distance were difficult. As a result, most of the rockets fired exploded either in front of or behind the bomber target. However, they did often achieve the effect of opening up the bomber formations enough for fighters to attack with conventional weapons. "Underwing mount (singly, one under each wing)"  "Underwing mount (two under each wing)"  "Under-fuselage mount (one each side, from bomb racks flanking nosegear well)"  "Outside the Luftwaffe"