Madsen Light Machine Gun
Principle of operation
The weapon is long-recoil operated and fires from the equivalent of an open bolt. The barrel and breech block frame coloured blue reciprocates inside the barrel jacket and receiver against the force of the return spring located inside the stock. The breech block (3) is a modified Martini type falling block which is pivoted towards the back of the breech block frame. The block has a raised position for ejection and a depressed position for loading through the side of the block in addition to the firing position shown. The block is tilted downwards as the barrel travels forward in order to load the new round and then moves upwards into battery just before firing. It moves further upwards to permit extraction as the barrel moves back under recoil. The position of the block is controlled by a small peg which engages in a switch plate in the right hand side of the receiver.
Starting from the position shown, the sequence of operation is as follows:
1. the hammer (4) is released and impacts the firing pin striker on the back of the breech block frame by the action of one of the springs in the stock.
2. the barrel and breech block move backwards under recoil against the resistance of the two springs in the stock. As the barrel moves backwards, the falling block moves upwards and extractor is tripped by a protrusion on the base of the receiver. The spent cartridge case is ejected against the curved undersurface of the block and deflected downwards through the trap door in the base of the receiver
3. As the barrel assembly reaches the end of its travel, the breech block falls. The barrel assembly and the hammer are detained by the sear unless the trigger is still pulled. In this case, the barrel assembly slides forwards under spring pressure and a new round rolls sideways into a groove in the left side of the block. The rammer(1) chambers the round as it turns around the circular feature (2) in the side of the receiver as the barrel moves forward under the action of the recoil spring. The block rises to the firing position and locks in position. The hammer is released after a short delay to hit the striker under the action of the second spring in the stock.
Here we see the switchplate which controls the position of the breechblock as the barrel assembly reciprocates in the jacket as follows.
(1) trigger pressed, (2) load, (3) breech block locked, (4) fire, (5) recoil, (6) eject, (A) dismantle
Although there is a three position fire selector, the weapon does not have a single round setting. On some models the three positions are labelled 'S', 'D' and 'F'. 'S' is Safe and 'F' is Fire (full auto). The 'D' (Decock?) position allows the trigger to release the barrel assembly to slide forwards, but not the hammer in order to clear the gun safely. The fire selector can not be moved unless the barrel/breech block assembly has been drawn back against the springs. This can be achieved by means of the large charging handle on the right hand side.
