Range was controlled by first adjusting the number of propellant charges. These could be attached to the fins of the round. The two large cylinders above the mortar tube accumulate gas vented from the breech during firing. This gas is then released to the exterior of the block through a flexible tube that would have been connected to a fitting on the short pipe that extends out from below the mortar tube.
The top hand wheel controls how much gas is vented from the breach. The lower hand wheel controls horizontal traverse of the entire mounting, thus controlling the direction of fire. The total traverse possible is 45 degrees.
The shells fired by the mortar were the FA 81mm model 1932. It weighs 3,3 kg and carried an explosive load of 350 to 400 gram. The maximum range was 2400m. It was fin-stabilized (six blades). The grenades had a deadly blast radius of around 10 meters.
The weight of the shell with its rocket RYG 24/31 amounts to 3.300 kg with a payload of explosive of 0.350 to 0.400 kg (maximum range: 2400m). In March 1936, trails are carried out with new tail design, in order to increase the range. This shell is the 81 FA model RF 1936, with a maximum range of 3,600 m. There were three types of ordnance: smoke, HE (high explosive) and AP (anti-personel).
42 Mortars were eventually installed in 21 turrets, and 86 were mounted in casemates for flanking or frontal fire.
During 1939-1940, a large number of accidents occurred in turret-mounted 81mm mortars (Metrich, Immerhof, etc.). The problem usually was a burst barrel pipe and early firings due to overheating of the cylinder head caused by too high a rate of fire.
|1)||Azimuth control wheel||2)||Gas release wheel|
|3)||Scope||4)||Gas release pipe|
|7)||Counterweight for shutter||8)||Breech block|