20x81 MG/FF cartridges

[pzgr40]

Cutaway models of 20x81 MG/FF cartridges. The Oerlikon MG/FF automatic cannon was designed in 1936 by the Ikaria Werke in Berlin, and was derived from the Becker 20mm gun from the First World War. The cannon was designed with the purpose that it could be placed in small spaces, such as airplane wings. The term MG/FF stands for 'Machine Gewehr / Flugel Fest' which means fixed wing mounting machine gun.
From 1941 onward, the 20x81 MG/FF was slowly phased out and replaced by the Mauser 20x81 MG 151/20, which had a higher rate of fire as well as a higher muzzle velocity.
The MG/FF gun was 1.37 meters long and weighed 26.3 kg. One of the disadvantages of using the M shell (Minengeschoss) was that it was lighter than the high-explosive, incendiary and armor-piercing shells, and since the MG/FF was a blowback weapon, this caused weapon failures in combined belts. For this reason, an MG/FF was modified for shooting M-shells with a lighter recoil spring. This weapon was referred to as the 20mm MG/FF/M. However, heavier grenades were not allowed to be fired from this weapon as this would damage the weapon.

The 20x81 MF/FF (/M) automatic cannon was used in the following aircraft; the Me-109E3 to F1 models (wings), the Fw-190A1 to A5 models, the Me-110 C to F models as well as upward firing cannons (schrage musik) built into the fuselage of the Me-110 night fighter. The cannon was built into bombers as a crew served aircraft defence weapon in the He-111 and the Do-17.

A disadvantage of the wing-mounted guns of the Me-109 was the limited ammunition capacity, the cartridges were supplied from a drum magazine with 60 cartridges, which with a firing rate of 530 rounds per minute meant that there was only 9 seconds of firing time. The Fw-A5 used a 90 round drum magazine, which provided a marginal improvement to 13 seconds of firing time. Since the 20mm MG-151/20 had a belt feed with 125 rounds, the 20mm MG/FF was slowly replaced by the 20mm MG-151/20.

Cutaway model 01
2cm Brandsprenggranatpatrone Leuchtspur FFM mit zerleger, 2cm High explosive incendiary shell FFM with tracer self destruct.

Projecile weight: 115 grams.
Filling: 2.3 grams of Nitropenta (pink) and 2.1 grams of Elektronthermit incendiary mixture (gray).
Fuze: AZ 1501 (nose fuze), under which a Duplex detonator is screwed.
Tracer length: approximately 1200 meters, self-destruct after 1200 meters.
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brass.
Powder charge: 13.2 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: Splinter- and incendiary effect.

Projectile color: yellow with a red band above the driving band (day tracer) or a dark red band (dim tracer/glimspur), and a green band just below the nose fuze, indicating that the projectile has a self-destruct mechanism.
The difference between Leuchtspur (tracer) and Glimmspur (dim tracer) is that tracers are used during daytime, and dim tracers at night. Dim tracers are less bright and this prevented the pilot whose eyes were used to the dark from being temporary blinded by tracers. When used during the daytime, dim tracers are barely to not visible at all.

The brass AZ 1501 is the first type of nose fuze used on the high-explosive grenade. The firing pin is blocked by a safety slide with a chamfered edge, held in the safe position by a vertical pin that is fixed in the upward position under the chamfered edge by a pellet of black powder. Sideways there are two primers placed above two firing pins which are kept away from the firing pins by a spring. When the shot is fired, the primers move backwards - due to the inertia effect - into the firing pins and ignite. The black powder pellet below the vertical pin is ignited through drilled channels and then burns away. The safety slide is thrown outwards by the centrifugal force and pushes the vertical pin down through with the chamfered edge. The firing pin is now free to move in the duplex detonator upon impact with the target. After 1942, the AZ 1501 is no longer mentioned in the German pamphlets.
If no target is hit, the brass container with the self-destruct charge (black) placed in the incendiary charge (gray) will ignite after the tracer has burned out and grenade will self destruct.

Cutaway model 02
2cm Brandsprenggranatpatrone Leuchtspur FFM mit zerleger, 2cm High explosive incendiary shell FFM with tracer self destruct.

Shell weight: 115 grams.
Filling: 2.3 grams of Nitropenta (pink) and 2.1 grams of Elektronthermit incendiary mixture (gray).
Fuze: AZ 1504 (nose fuze), under which a Duplex detonator is screwed.
Tracer length: approximately 1200 meters, self-destruct after 1200 meters.
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material : brass.
Powder charge: 13.2 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: splinter and incendiary effect.
Projectile color: yellow with a red band above the driving band (day tracer) or a dark red band (night tracer/glimspur) and a green band just below the nose fuze indicating that the grenade has a self-destruct mechanism.

The aluminum AZ 1504 is the successor to the AZ 1501. The fuze body (3) is fully aluminum made. A steel firing pin (5) is positioned sideways, out of alignment with the duplex detonator and cannot strike it when safe, because a steel ball (10) rests above the hole above the duplex detonator. The firing pin (5) is placed in a kind of 'yoke-shaped' magnesium safety slide (4) with a recess for the steel ball in the base. From the bottom of the lower part of the fuze body, a hole has been drilled in the longitudinal direction that extends outwards at an angle of two degrees - viewed upwards-. Two radially placed steel pins (6) are placed under the safety slide that prevent the ball from moving upwards when safe. These two pins are held in the inner position by a band spring (7). After the shell is fired, the two pins (6) move outward due to the centrifugal force, and the steel ball (10) starts to climb up against the sloping side of the hole through the centrifugal force after acceleration decreases until it enters the recess in the bottom of the safety slide (4). As a result, the safety slide suddenly becomes heavier on this side and is thrown outwards, the firing pin being slided above the duplex capsule. Upon impact, the striking pin (2) pushes the firing pin (5) in the duplex detonator, causing the shell to explode.
If no target is hit, the brass container with the self-destruct charge (black) placed in the incendiary charge (gray) will be ignited by the tracer after the tracer burns out and destroy the shell.

Cutaway model 03
2cm Brandsprenggranatpatrone Leuchtspur FFM ohne zerleger, 2cm High explosive incendiary shell FFM without tracer self destruct.

Projectile weight: 115 grams.
Filling: 2.3 grams of Nitropenta (pink) and 2.1 grams of Elektronthermit incendiary mixture (gray).
Fuze: AZ 1504 (nose fuze), under which a Duplex detonator is screwed.
Tracer length: approximately 1200 meters
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brass.
Powder charge: 13.2 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: splinter and incendiary effect.
Projectile color: yellow with a red band above the driving band (tracer) or a dark red band (dim tracer).

Cutaway model 04
2cm sprengranatpatrone Ub FFM ohne zerleger, 2cm practice high explosive shell FFM without self destruct.

Projecile weight: 115 grams.
Filling: none.
Fuze : none.
Tracer length : none
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brass.
Powder charge: 13.3 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: none.
Projectile color: gray.

Cutaway model 05
2cm Sprenggranatpatrone L’spur Ub FFM mit zerleger, 2cm practice high explosive shell FFM with tracer self destruct.

Projectile weight: 115 grams.
Filling: Nitropenta with black powder ignition charge by means of a tracer self-destructor. Above the Nitropenta charge a Bakelite filler piece is placed.
Fuze: dummy nose fuze.
Tracer length: 650 meters.
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brass.
Powder charge: 13.3 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: none, intended for exercises with a limited shooting range.
Projectile color: gray with red band just above the guide band and a green band just below the dummy fuze fuze.

Cutaway model 06
Sprenggranatpatrone L’spur Ub FFM ohne zerleger, 2cm practice high explosive shell FFM without tracer self destruct.

Projectile weight: 115 grams.
Filling: none.
Fuze: dummy nose fuze.
Tracer length: 650 meters.
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 13.3 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: none, intended for practice firing.
Projectile color: gray with a red band just above the driving band.

 

[pzgr40]

Cutaway model 07
2cm brandgranatpatrone Glimspur FFM ohne zerleger, 2cm Incendiary FFM without self destruct.

Projectile weight: 115 grams.
Filling : 6.1 grams electron thermite.
Fuze : AZ 1528 or AZ 1528 A.
Tracer length: 1100 meters.
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 13.3 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: Incendiary.
Projectile color: Blue, with dark red band (dim tracer) above driving band.

The projectile body is the same as the Explosive incendiary shell without self destuct mechanism, only now completely filled with a pressed-in Elektronthermit mixture. The aluminum AZ 1528 fuze has no safety mechanism, but only a pressed-in detonator 1452 in the nose. On impact with the target, the detonator 1452 ignites the incendiary charge and blows the aluminum AZ 1528 fuze body off the shell body, after which the shell burns empty, spewing a meter-long fire jet forward for a few seconds.

Cutaway model 08
2cm panzersprengranatpatrone FFM ohne zerleger, 2cm armour piercing high explosve shell FFM without self destruct.

Projectile weight: 115 grams.
Filling: 4 grams Nitropenta
Fuze: base fuze BDZ 1512 or 1513.
Tracer length: none.
Vo: 585 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 13.3 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: Armor piercing High explosive
Projectile color: black, with yellow band 2cm below the nose.

The nose of the shell body is hardened to just below the ogive.

The Bdz.1513 is an aluminum base fuze which is activated by inertia upon impact. The firing cap housing is placed in an aluminum tube with two opposite radial holes drilled in the lower part. The firing cap housing has a semi-circular groove machined in at the lower part. Two steel balls are placed half in the two holes and half in the semicircular groove and fixate the firing cap housing in the lower position when safe. A band spring forces the balls in the inner position. An axial directed slot has been milled into the top of the aluminium tube into which a sheet metal firing pin is placed, with the tip of the firing pin pointing downwards in the direction of the firing cap. The fuze mechanism is locked up by a screw-in cover in top of the fuze body in which a small hole of 0.1 mm diameter has been drilled in the center. The heat-sensitive detonator 'sprengkapsel 3801' is placed in the explosive charge above the fuze.

When the shot is fired, the steel balls are thrown outward by the centrifugal force, pushing the band spring open. The firing cap housing has now been released. Upon impact, the firing cap housing moves forward by inertia, forcing the firing cap into the firing pin. The flame of the firing cap must now move through the 0.1 mm diameter hole in the fuze cover into the detonator 3801, but as pressure must first be built up in the space around the firing pin, this results in a delay that is necessary to allow the shell to pass through the armor, before the shell explodes within the target.
The fuze is activated by striking a 5mm thick steel plate, and has an armor piercing capacity of up to 10mm of steel at a distance of 100 meters.

Cutaway model 09
2cm Pantserbrandgranatpatrone (Phospor) FFM ohne zerleger, 2cm Armour piercing incendiary (white phospor) FFM without self destruct.

Projectile weight: 115 grams.
Filling: 3.6 grams of white phosphorus in an aluminum capsule
Fuze: none.
Tracer length: none
Vo: 585 meters/sec.
Shellcase lenth: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 13.2 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 183 grams.
Effect: armor-piercing incendiary.
Projectile color: black with a blue band 2cm below the nose and the letter Ph stenciled in white on the projectile body.

The nose of the projectile body is hardened to just below the ogive.
The projectile body is the same projectile body as the armour piercing high-explosive shell.
An aluminum capule filled with white phosphorus is placed in the grenade body. Upon impact with a steel plate, the grenade body breaks into pieces and the burning phosphorus is dispersed into the target, causing a fire.
Penetration: 10mm steel at an angle of 60 degrees, 22mm at 90 degrees.

 

[pzgr40]

Cutaway model 10
2cm Minen geschoss patrone FFM ohne zerleger, 2cm Mine shell FFM without self destrct mechanism.

Projectile weight: 92 grams.
Filling: 20 grams HA 41.
Fuze: AZ 1502 with duplex detonator VC70.
Tracer length: none
Vo: 718 meters/sec.
Length of shellcase: 81 mm.
Shellcase material: brass.
Powder charge: 15 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 157 grams.
Effect: blast and incendiary effect
Projectile Color: Yellow with a black letter M painted on the projectile body.

The Mine shell has virtually no splintering effect, but a large blast effect that rips away sheet metal from aircraft skin. In combination with the VC70 duplex detonator, which provides a 10cm flight path delay, the shell first pierces the target before detonating within the fuselage or wing of an aircraft. This allowed up to a square meter of sheet metal to be ripped away from an aircraft. The explosive HA 41 consists of 59% Hexogen, mixed with 41% fine aluminum powder that strengthens the blast effect as well as the incendiary effect.
In way of the driving belt, an aluminum ring is fitted in the explosive charge that prevents the driving belt and the shell body from being pushed inwards during barrel passage, which would result in pressure loss.

The AZ 1502 fuze is a steel nose fuze in which the firing pin (nail) is fixed by a brass coil (spirale). When the shot is fired, the brass spiral opens, allowing the firing pin (nail) to move freely. On impact, the thrust pin (stossel) in the nose pushes the firing pin in the VC70 detonator.

The VC70 duplex detonator consists of an aluminum housing in which a dumbbell-shaped insert piece is placed in top, with an impact-sensitive (for firing pin) primer placed in the top, and a heat-sensitive detonator (red) in the bottom. Both primer and detonator caps have a radially drilled channel of 0.1mm drilled into opposite sides. These channels end in the narrowed part of the dumbbel shaped piece. Upon impact on the target, the firing pin ignites the primer. The flame is pressed through the channel and ends in the narrowed part. The flame builds up pressure until the flame reaches the heat-sensitive detonator through the opposite channel at the bottom and ignites it. This primer ignites the main charge of the detonator which ignites the main charge of the shell.

Cutaway model 11
2cm Minen geschoss patrone FFM mit zerleger, 2cm Mine shell FFM with self destruct mechanism.

Projectile weight: 92 grams.
Filling: 20 grams Nitropenta.
Fuze: ZZ 1505 with duplex detonator.
Mechanical self-destruction: between 900 and 1200 meters
Vo: 718 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brass.
Powder charge: 15 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 157 grams.
Operation: Blast.
Projectile color: yellow with a black letter M painted on the projectile body and a green band just below the fuze.

The Mine shell has virtually no splintering effect, but a large blast effect that rips away sheet metal from aircraft. The explosive charge consists of Pentrite, a powerful explosive with a detonation speed of 8700 m/sec. This M-shell uses the normal duplex capsule, which means that the grenade detonates immediately upon impact.
In way of the driving belt, an aluminum ring is fitted in the explosive charge that prevents the driving belt and the shell body from being pushed inwards during barrel passage, which would result in pressure loss.

The ZZ 1505 (Zerlege Zunder) is a fuze with a mechanical self-destruct device. When the shot is fired, eight steel balls (8 kugeln) are thrown outward by the centrifugal force into the groove of an intermediate ring (zwischenring), whereby the housing of the steel balls (kugelhalter) is moved upward 0.1 mm. This releases the brass spiral (spirale), which rotates open due to centrifugal force, after which the two halve flyweights (fliehstucke) that fix the firing pin (nadel) in the upper position also move outwards. An equilibrium is now created; If, due to the centrifugal force, the force of the eight balls in the groove of the intermediate ring is greater than the force of the pressure spring (druckfeder) above it that wants to press the firing pin into the duplex detonator, the shell will continue its trajectory, but if the speed -and as a result the centrifugal force- of the shell decreases, this will result in a moment where the force of the spring overcomes the force of the 8 steel balls in the groove of the intermediate ring, pushing the steel balls back into the housing for the steel balls and thus the firing pin into the duplex detonator, after which the shell detonates.
However, when a target is hit, the housing of the steel balls is driven inward with such force that the steel balls are instantly pushed back into the housing and the firing pin is pushed into the duplex detonator, after which the grenade detonates.

Cutaway model 12
2cm Minen geschoss Patrone FFM mit zerleger, 2cm Mine shell FFM with self destruct mechanism

Projectile weight: 92 grams.
Filling: 20 grams HA 41.
Fuze: ZZ 1505 with duplex detonator VC70.
Mechanical self-destruction: between 900 and 1200 meters
Vo: 718 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 15 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 157 grams.
Operation: Blast and incendiary
Projectile color: yellow with a black letter M painted on the projectile body and a green band just below the fuze.

The Mine shell has virtually no splintering effect, but a large blast effect that knocks away sheet metal from aircraft skin. In combination with the VC70 duplex detonator, which provides a 10cm flight path delay, the shell first penetrates the target before detonating within the fuselage or wing of an aircraft. This allowed up to a square meter of sheet metal to be ripped away from an aircraft. The explosive HA 41 consists of 59% Hexogen, mixed with 41% fine aluminum powder that strengthens the blast effect as well as the incendiary effect.
In way of the driving belt, an aluminum ring is fitted in the explosive charge that prevents the driving belt and the shell body from being pushed inwards during barrel passage, which would result in pressure loss.
Cutaway model 13
2cm Brandgranatepatrone 44 FFM ohne zerleger, 2cm incendiary cartridge 44 FFM without self destruct.

Projectile weight: 106 grams.
Filling: 18 grams HA 41.
Fuze: AZ 9501 liquid activated igniter.
Vo: 718 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 13.3 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 157 grams.
Effect: Blast and Incendiary effect upon contact with (liquid) fuel.
Projectile color: unknown.

The purpose of the incendiary grenade 44 is to pierce fuel tanks, after which the liquid-activated fuze AZ 9501 ignites the grenade by means of fuel that flows into the fuze. The incendiary effect is provided by the aluminum powder mixed in the explosive charge. The shell body has a thicker wall than the regular M-shell which results two grams less explosive in the shell body.
The fuze is pressed directly into the shell body, and not screwed into the internally threaded ring that the normal M-shell uses. This simplifies production.

The AZ 9501 has a pointed steel fuze body with four radial angled holes drilled at 90 degrees each. A filler piece (fullstuck) is placed over the fuze body, over which a thin tin cap (kappe) is placed. A firing pin (nadel) is placed in the fuze body, which is fixed in the upper position by a brass coil (spirale). The firing pin and the brass spiral are placed over the closing screw (abschlus schraube). The duplex detonator is screwed in under the closing screw.
When the grenade is fired, the brass spiral opens, releasing the firing pin. Upon impact with the sheet metal of an aircraft, the tin cap and filler piece are pulverized. When piercing the fuel tank, the fuel will flow into the four holes at high speed, pushing the firing pin into the duplex detonator, causing the shell to explode.

Cutaway model 14
2cm Mine geschoss Patrone Ub FFM ohne zerleger, 2cm practice M-shell FFM without self destruct mechanism.

Projectile weight: 92 grams.
Filling: coal tar mixed with iron powder.
Fuze: ZZ 1505 fuze body without inner parts.
Mechanical self-destruction: none.
Vo: 718 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brown muffled steel.
Powder charge: 15 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: 157 grams.
Effect: none.
Projectile color: painted entirely gray.

Practice version of the M-shell intended for target practice.

Cutaway model 15
2cm Minen geschoss Patrone Ub FFM ohne zerleger, 2cm practice M-shell FFM without self destruct mechanism.

Projectile weight: unknown.
Filling: none.
Fuze: dummy fuze.
Mechanical self-destruction: none.
Vo: 718 meters/sec.
Shellcase length: 81 mm.
Shellcase material: brass.
Powder charge: 15 grams of Nz Bl.P (Nitrocellulose Leaf Powder).
Cartridge weight: unknown.
Effect: none.
Projectile color: painted entirely gray.

Practice version of the M-shell intended for target practice, without filler.
The grenade body is made of a harder and tougher grade of steel, apparently eliminating the need for an aluminum support ring i.w.o the driving band. The pressed nose cap is zinc made.

Regards, DJH

 

[Weasel Pilot]

Wow! From soup to nuts, an amazing primer on this weapon and its ammunition! Thank you. Great cutaways, too BTW.