20mm MG FF. Was it so bad?

davebender

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Popular histories often bad mouth the 20MM MG FF cannon. But was it really that bad during 1939 to 1941, when it was superceded by the superior MG151/20?

MG FF.
26 kg.
60 round drum magazine. Later a 90 round drum magazine.
540 rounds per minute.
700 mps velocity for 20mm mine shell.

MG151/20.
42 kg.
Belt feed.
740 rounds per minute.
805 mps velocity for 20mm mine shell (same projectile as MG FF).

The German 20mm mine shell contained 18.6 grams of HE filler. Three times as much as early model HS.404 cannon shells.

700 mps velocity is probably more then adequate for typical fighter combat ranges of 200 meters or less during the early WWII period. The 20mm mine shell was very powerful so you don't need to spray for long if you are on target.
 

mikewint

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MG FF had some disadvantages, such as low rate of fire and low muzzle velocity, as well as limited ammunition storage in its drums. On the other hand, it was much lighter and shorter. Wing installation on the Messerschmitt Bf 109 and Focke-Wulf Fw 190 fighters was not easy, as the drum required substantial space, and as a consequence the ammunition storage was initially reduced to 60 shells per drum. An ammunition drum of 90-round nominal capacity was developed for the Fw 190 A-5, and retrofitted to some earlier variants. There were also experiments with belt feedings.

The MG FF was adapted to fire a new type of high-capacity, high explosive mine shell, called Minengeschoss that featured a projectile with thinner walls that allowed increased explosive charge. This projectile was lighter and generated less recoil than earlier projectiles requiring a modification of the recoil mechanism. With this modification it could fire the new mine shell, but accidentally using the heavier MG FF ammo could damage the gun. The now-called MG FF/M was introduced with the Bf 109 E-4 and Bf 110 C-4 in Summer 1940.
It saw a come-back in 1943 as the primary Schräge Musik gun in the Bf 110 night fighters, as it perfectly fitted into the rear cockpit.

I can certainly see where low rate of fire, low velocity, and reduced ammo capacity would be a severe disadvantage to aircraft. Add to that the occasional OOOPS when the wrong ammo is loaded into a modified version
 
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davebender

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The MG151/20 projectile was only 105 meters per second faster. How much does that matter when the target is less then 200 meters away?
 

weinace

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Jan 4, 2009
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I believe it was to be installed in the Ta152C-4 C-5, can't have been a total write off??
 

tomo pauk

Creator of Interesting Threads
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MG FF was not produced in 15mm calibre - MG 151 it was.

As for the FF, the cannon was fine for 1939/40, since it enabled light weight fighter to have a good punch. The low ammo count was not a very good thing to have when trying to achieve air superiority over enemy territory, though.
 

The Basket

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The MG FF was used in Schräge Musik installlation because they were available.

a 20mm is still a 2cm.
 
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Glider

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For what its worth I always felt that the FF doesn't get the praise that it deserved. It wasn't the best 20mm in the world but doesn't mean that its a bad gun.

It had two major benefits
The first benefit is that its a light gun, weighing less than the 0.50 M2, granted it didn't have the MV, ROF or ballistics of the M2 but it fired a much larger shell and at the range of most air combat, the MV and Ballistics weren't a major issue.

Secondly and most importantly, it enabled the Luftwaffe to field an effective 20mm when most other countries were using LMG or paired HMG. Timing is vital and by the time that other nations were ready to deploy 20mm guns the Luftwaffe were able to move up to the 20mm 151. For a 1940 fighter the Me109 E3 had formidable firepower, you would be hard pushed to find a fighter of that period with a more effective armament.
 
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davebender

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IMO France was the only nation with a better fighter weapon during 1939 to 1940. And even that is debatable since the MG FF fired a much more destructive projectile then the HS.404 cannon.
 

mikewint

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The Fw 190 was typically fitted with an inboard pair of MG 151 and an outboard pair of MG FF, although the MG FF were sometimes removed in the field in order to save weight. The cannon was also fitted to bombers such as the Do 217, Ju 88, He 111, Do 17 and others
 

tomo pauk

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IMO France was the only nation with a better fighter weapon during 1939 to 1940. And even that is debatable since the MG FF fired a much more destructive projectile then the HS.404 cannon.

MG FF/M was the one that fired Minnegeschoss ;) - HS-404 was better if we compare balistic destruction properties vs. MG FF. The HS was also installed as an moteur-cannon, making it less likely to miss a target that happened to be far away from harmonizating distance.
But Bf-109 carried two cannons,compared with 1 caried by French fighters - in practice canceling out any advantage MS-406 D.520 might have re. cannon.
 

Shortround6

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Popular histories often bad mouth the 20MM MG FF cannon. But was it really that bad during 1939 to 1941, when it was superceded by the superior MG151/20?

MG FF.
26 kg.
60 round drum magazine. Later a 90 round drum magazine.
540 rounds per minute.
700 mps velocity for 20mm mine shell.

It doesn't appear that the fighters ever used the 90 round magazine. So it is 60 rounds per gun at best except for a few specialized installations. Different sources give different rates of fire of the MG//FF which may help account for it's bad reputation, even if not quite factual. The light "mine" shell also means that once it starts being used and guns modified they could not use the old the ammo and new types of AP and tracer needed to be developed. Not a big problem in itself but the AP and Tracer ammo had rather different weights and muzzle velocities than the 'mine' shell and rather different times of flight. Not a problem if you get in really close but not a good thing either.
 

Shortround6

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I believe in 1939 it was the MG/FF with the heavy/slow shell. In the Spring of 1940 the MG/FFM shows up.
The MG/FF in either version is not a bad weapon for 1940, it just doesn't have much development potential ( although the Japanese managed some improvements to their version of the basic gun).
The Ammunition for the MG/FF was sort of either/or. You either had penetration or you had blast, not both in the same round. While the mine shell did have a lot of blast it had little penetration. The Hispano (once they got the fuse situation sorted out) could penetrate light protection/structure and detonate behind it.

Getting better than 60 round drums in the wing presents problems. You either need a bigger drum (harder to hide in the wing) or you have to jam more shells in the same space. Possible but might require work for reliability. ME 110s of the time used the radio operator to change 60 round (55?) drums instead of using larger drums/feeds in the fuselage mounted 20mm MG/FFs-Ms they used.
 

davebender

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Why does that matter?

The superior MG151 was under development during 1937. When it enters mass production the stop gap MG FF mostly disappears from service. Pouring money into MG FF development would be money down the drain.
 

CharlesBronson

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MG FF was not a bad weapon but you need to get close to aim correctly.

The MG151/20 projectile was only 105 meters per second faster. How much does that matter when the target is less then 200 meters away?

It matters because two things:

a) The Time of flight is the MG 151/20 projectile is lesser so any manouvering target would be easier to hit.

b) The kinetic energy transfered to the target is far superior...how much with 105 mps more ? a lot more imagine being hit in the chest by a tenis ball at 50 meters per second, then being hit by a tenis ball at 205 meters per second....you will noticed the difference believe me.

Of course kinetic energy is big deal for armor piercing bullet , less important in High explosive shell, but still the bullet had to punch trough some alluminium in order to explode.

Still the MG FF had a lot of use, specilly in strafing attacks, the Me-110Cs of SKG 210 claimed a lot of light tanks destroyed by cannon fire in June-july 1941. of course those were shallow dive attack when the speed of the bullet id "helped" by the speed of the fighter itself, the Panzergranate ammunition of the MG FF and FF/M could pierce 20-22 mm of armor in that conditions.
 

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Shortround6

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a) The Time of flight is the MG 151/20 projectile is lesser so any manouvering target would be easier to hit.

b) The kinetic energy transfered to the target is far superior...how much with 105 mps more ? a lot more imagine being hit in the chest by a tenis ball at 50 meters per second, then being hit by a tenis ball at 205 meters per second....you will noticed the difference believe me.

It is not that bad but kinetic energy does change with the square of the speed so roughly 59X59= 3841 compared to 70X70 = 4900 for about a 27% increase in kinetic energy.
 

CharlesBronson

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It is not that bad but kinetic energy does change with the square of the speed so roughly 59X59= 3841 compared to 770 = 4900 for about a 27% increase in kinetic energy.

Thansk for the calculation, by the way 50 plus 105 is 155 mps, I can vow, I completed my elementary school.

You need to do that anyway until gryo stabilized gunsights become standard equipment during the last year of the war.
Gyro gunsights were a completely inexistent item in German fighters with teh sole exception of a dozen of Me-262 and Ta-152s.
 

elbmc1969

Senior Airman
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Feb 16, 2019
It is not that bad but kinetic energy does change with the square of the speed so roughly 59X59= 3841 compared to 70X70 = 4900 for about a 27% increase in kinetic energy.
Assuming that kinetic energy is the measure of merit. Williams and Gustin make an extensive analysis showing that momentum actually determine impact lethality, modified by explosive content. If kinetic energy is the determining factor, the German adoption of the MK108 is insane. You'd also expect some incredible differences in shootdowns that aren't supported by the evidence.

A short version of Williams and Gustin's analysis is here: WORLD WAR 2 FIGHTER GUN EFFECTIVENESS
 

Shortround6

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Assuming that kinetic energy is the measure of merit. Williams and Gustin make an extensive analysis showing that momentum actually determine impact lethality, modified by explosive content. If kinetic energy is the determining factor, the German adoption of the MK108 is insane. You'd also expect some incredible differences in shootdowns that aren't supported by the evidence.


Neither Kinetic energy or momentum are really good indicators of damage done as a lot depends on what is hit. For penetrating armor (or substantial structural members) then Kinetic energy may be preferable. For thin or light metal then the high energy projectile sails right on through and out the other side expending it's energy on the clouds or the ground below.

One can go to either extreme and quote examples of each type of projectile/gun not working.

The MK 108 was an explosive delivery device. They never intended it to shoot through much of anything much thicker than aircraft skin.

the 12.7 to 15mm caliber area was the change over from kinetic energy to chemical energy.
 

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