Luftwaffe Cannons and Machineguns topic.

[CharlesBronson]

You also referred to "the shorter stroke in the bolt's travel" which would olnly be possible with a shorter cartridge: the bolt stroke length is directly linked to the overall cartridge length.

Yes, now I see that having the same cartrigde overall lenght the gun need to have the same bolts stroke lenght in order to feed it. Quite logic. Several sources claim a bigger rate of fire in the 20mm variant however.

 

[Erich]

CB again the under weapons pod was short lived. Granted it had much firepower , maybe too much similar to the He 219 a reason the crews had half of the cannons removed. the same applies for the Bf 110G-4 it was already overladen with radar/radio equipment and the four cannons were enough to take down any Allied bomber. In the photo you can imagine the loss of total air speed in trying to overtake an RAF heavy

E

 

[CharlesBronson]

Jawol, I would be suprized if that Messers can reach the 500 km/h.


MG 151 Family part 3, MG 151/20 Elecktrish.

The differences with the normal MG-151/20 was purely internal. The spring loaded firing pin was replaced with a fixed needle wich was energizated by the 24v aicraft electric circuit. The sincronization device consisten in a electromechanical gear, the use of electricar primer wich was detonated by a spark, mean that a more instantaneous ignition was provided. That allowed the MG 151/20E to shoot through a high rpm 3 thick blade propellers like the BMW 801 engine and still had a rate over the 600 rpm. The production of the Mg-151/20E were delivered almost entirely to the Fw-190 and the Ta-152H variants, some other aircraft in use were the Do-335 ( 2 above the engine), Me-209 stüfe II (wingroots) and the Me-309 (wingroots and above engine)

The 4 guns in a FW-190A-6.

Experimentally the fitting of an MG 151 pod under the fuselage to fire through the prop was tested. This apparently worked very well, providing a valuable improvement in firepower without the performance and handling penalties of the underwing pods. However, the belly gun had to be synchronised, which meant it had to use the electric-primed gun, whereas the engine gun used percussion priming. The risk of mixing up the ammo was considered too great, so the idea was dropped

MG 151/20E below Bf-109G-4.

 

[Denniss]

BTW the image of a Bf 109 G-4 with underwing gun pod is not af a G-4/R6 but of a G4 with Rüstsatz 6.
R6 (Rüststand 6) would denote an all-weather capable fighter which had some special navigation and radio equipment.

 

[CharlesBronson]

Hmmmm...sure about that ?

 

[Denniss]

Adding a Rüstsatz never changed an aircraft designation, the /Rx designation always refers to Rüststand.
For the 109G, R1 was a fighter-bomber (probably with two drop tanks under the wing and a bomb on the centerline wing rack or at least with underwing bomb rack for smaller bombs of the 50kg type), R2 to R5 were different recon variants.
Then we have the /U designation for Umbausatz or Umrüstsatz, U1 is a special prop, U2 is GM-1 injection, U3 should be either MW-50 or another recon variant (it is said that MW-50 was used in the G-6 by using /U2 variants with a modified tank), U4 is the MK 108 engine cannon

 

[genkideskan]

Well the synchronisation was the reason to develope the MG 151. Its not possible to synchronise an FF properly. Aircraft used MG 151 used mostly electrical primed ammo. The primer wasnt ignite by spark but by an thin wire that becomes red hot and ignite a primer pellet. The syncronised guns used a special tested round. These rounds where marked "gest". These means "gesteuert" and indicates ammo that was reliable enouth to fire through the prop. The outer guns used normal ammo but electrical ignited, too.

 

[CharlesBronson]

Adding a Rüstsatz never changed an aircraft designation, the /Rx designation always refers to Rüststand.
For the 109G, R1 was a fighter-bomber (probably with two drop tanks under the wing and a bomb on the centerline wing rack or at least with underwing bomb rack for smaller bombs of the 50kg type), R2 to R5 were different recon variants.

Whatever, I always saw the R6 designation refered to the underwing Mausers.

Well the synchronisation was the reason to develope the MG 151. Its not possible to synchronise an FF properly. Aircraft used MG 151 used mostly electrical primed ammo. The primer wasnt ignite by spark but by an thin wire that becomes red hot and ignite a primer pellet. The syncronised guns used a special tested round. These rounds where marked "gest". These means "gesteuert" and indicates ammo that was reliable enouth to fire through the prop. The outer guns used normal ammo but electrical ignited, too.

Too many variables in the ammo, I guess thats why the allied used few sinchro weapons.

 

[Tony Williams]

Well the synchronisation was the reason to develope the MG 151. ... Aircraft used MG 151 used mostly electrical primed ammo.

Not really. Only the Fw 190 family used electrically-synchronised MG 151 in service, I believe. The first installation was as an engine gun in the Bf 109, and that used percussion priming.

 

[Tony Williams]

Too many variables in the ammo, I guess thats why the allied used few sinchro weapons.

The principal reason was that the Allies started the war relying on machine guns (the USAAF continued to do so, for the most part), and had to mount several of them to get sufficient destructive effect. They couldn't all fit around the engine, so it made sense to standardise the installations and put them all in the wings. Also, the Browning fired much more slowly when synchronised. Finally, the Hispano could not be synchronised at all.

 

[genkideskan]

I always wonder about the use of 7,7 cal. and .50 use - there is no place for explosive. May be its enouth to bring down early bombers HE 111 and Do's.
I wouldt like to know how many bursts a Hurricane or Spitfirw wouldt need to bring down a B-17 with the 8 x .303 guns.
There is a need for Germany to use canons in 20mm or in 1943 30mm and larger. It was nessessary to bring as much as possible explosive into the target.
So the 30mm becomes standard and a lot of MG 151 becomes free for other tasks, f.e. as AA guns. Late war development brings the MG 213 in 20mm. These gun used an extended case and was designed for the Mine X projectiles
and a rate of fire beyond 1200 rd./m. Than the 20mm was dropped and the 30mm version shouldt become the german main gun.
Annother feature of the MG 151 was the low recoil -always a problem in aviation. The use of an electrical priming system make it possible to realise an ignition exactly 8mm befor the forward move of the barrel and bolt was finished. So the gun fires when most of the moveable parts of the gun are still in move forward. That swallows a lot of recoil.
BTW I was told that a Spitfire burst of all 8 guns produced an recoil that costs you about 40 miles of speed. Any idea ?

 

[Tony Williams]

BTW I was told that a Spitfire burst of all 8 guns produced an recoil that costs you about 40 miles of speed. Any idea ?

Absolutely not. This is what I put in Flying Guns – World War 2: Development of Aircraft Guns, Ammunition and Installations 1933-45:

"This might be an appropriate moment to dispel one of the favoured myths of big-gun aircraft; that the recoil had a drastic effect on their speed. To take the example of the USAAF's B-25 fitted with a 75 mm M4 gun; the aircraft weighed around 12,000 kg and attacked at perhaps 400 km/h, the gun fired a 6.8 kg projectile at around 2,200 km/h. A simple rule of thumb is to multiply the weight by the speed to achieve a rough "momentum index" (it is actually a bit more complicated than this, as the expanding propellant gasses contribute to the recoil). It will be apparent that the aircraft has at least 200 times the momentum of the projectile, and a single shot will therefore not greatly slow it. In fact, at the end of an attack run in which several shots were fired, the plane would typically be slowed by 10-15 mph. The effect on fighter speed of long bursts of heavy gunfire (especially from automatic cannon) could be noticeable, particularly in a turning battle when the aircraft might be manoeuvring at the extremes of the flight envelope, close to stalling."

 

[CharlesBronson]

The principal reason was that the Allies started the war relying on machine guns (the USAAF continued to do so, for the most part), and had to mount several of them to get sufficient destructive effect. They couldn't all fit around the engine, so it made sense to standardise the installations and put them all in the wings. Also, the Browning fired much more slowly when synchronised. Finally, the Hispano could not be synchronised at all.

Incidentally the Bell P-39 and the early P-40 have sincro MGs but according t the pilot it jammed a lot more than desirable. I was aware of the simple recoil weapons like the Oelikon were not suited for shot trough the propellors, ididt know about the Hispano.

Do you have any figure of RPM for the Browning sincro M2 mounting ?



15x96mm Ammunition for the MG-151/15.

Panzergranatpatrone, L-spur.

Armor piercing steel shot, with tracer, projectile weight 72 grams initial speed 850 m/s. The tracer elemente endure at list 1100 meters.

Penetration table for Pzg.Ptr. L-spur. 25 mm at 100 meters and 13 mm at 600 meters, both in vertical (90º) plate and direct mode..

Brandsprenggranatpatrone

Incendiary-explosive. 57,5 grams bullet, muzzle velocity 960 m/s, pretty fast one.


Brandsprenggranate L-spur Mit Zerl.

Same as above but with an tracer and self destruction element in the bullet base. Green

Hartkern-Panzergranate ohne-zerl.

This is a pretty unusual variant. It consist in a miniaturized hard core Panzergranate 40 as used in the Panzers. Bullet weight 53,5 grams, it had an 9,5mm diameter tugsten-carbide core with a aluminium-magnesium envelope. It was propelled by 24,5 grams of gunpodwer an it can reach 1000 m/s. Due his cost a relative rarity it was to combat tanks only, no for air-to-air use. Probably it went to the Hs-129B-1 attack craft, and for some experimental 15 mm antitank rifles.



Penetration table of the Hartkern 15 mm bullet, 48mmm at 100 meters in a 160 kg/square mm steel ( wich is equivalent to a SAE 4340 alloy), excellent figure...

 

[Tony Williams]

Incidentally the Bell P-39 and the early P-40 have sincro MGs but according t the pilot it jammed a lot more than desirable. I was aware of the simple recoil weapons like the Oelikon were not suited for shot trough the propellors, ididt know about the Hispano.

To be effectively synchronised, a gun required a short "lock time"; the delay between the gun receiving the message to fire and the cartridge actually firing. This had to be as short as possible, in order to provide the precision needed to avoid hitting the propeller.
A lot of MGs and cannon (the Hispano included) fired from an open bolt; the starting position for the gun was with the chamber empty and the bolt held back. When the gun received the message to fire, the bolt was released, began to move forwards, picked up a cartridge, loaded it into the chamber, locked up the action and, only then, fired. This took far too long. There were a few open-bolt guns which retained a separate control of the firing pin (the MG 17 was one) which did enable them to be synchronised.

Do you have any figure of RPM for the Browning sincro M2 mounting ?

The Browning fired from a closed bolt (except for the British .303 version) but still lost a lot of performance in the big .50 calibre, possibly because the firing pin assembly was heavy and took some time to move forward to fire the cartridge. I have seen figures of 400-450 rpm in its synchronised form.

 

[CharlesBronson]

Thanks, I really preciated your input Tony.

 

[CharlesBronson]

20x82mm ammo for MG-151/20.

http://i17.tinypic.com/42ukmle.jpg

This was the result of the necked up 15mm cartrigde, it was available with brass or steel case, the steel being favored because the always problematic copper resources, more than 80% of the cases wre fabricated in the metal. The ammo for the E variant used a electric primer, the other an standar percusion primer. There was at list 30 variant of projectile for 20x82mm cartrigde including several ubung (exercise) ones, for space reason I will only post the most used in wartime,


Brandsprenggranate glimmspur mit Zerleger.

Explosive-incendiary, with glowing tracer and self destruction fuse, a "working" ammo for the MG-151/20. Bullet weight 115 grams, explosive content 6 grams, the self destruccion device actuate after 1100 meters from the muzzle, o 3 seconds in flight. Muzzle speed about 720 m/s.
http://i13.tinypic.com/2mz9wsw.jpg

Minengesschos.

The thin walled explosive projectile from the FF/M adapted to the MG-151, Weight 92 grams, muzzle speed 785 m/s.


Minengesschos mit Zerleger.

Same as above but with an self destructing device, indicated by a green band stenciled in the bullet. A good decition specially in later war when most of the air combat were fought over the homeland.


Panzersprenggranate.

Armor piercing-explosive, weight 117 grams , muzle velocity 705 m/s. A steel shot with a 5 grams of nitropenta, base fused. Explosive content indicate by a yellow band.


Penetration table por the 20 mm Pzgr. 24 mm at 100 meters (90 º incidence) in 140 kg/squre mm steel, equivalent to a SAE 4140 alloy. The discontinued line indicated penetration after get trough a 3 mm 20 º tilted duraluminium plate.

Panzergranate mit Phosphor

Armor piercing incendiary, filled with an red and white phosphorous mix. 117 grams bullet, muzzle speed 705 m/s.


Panzergranate-Elektron.

AP incendiary, 117 grams, filled with a incendiary mix called "Elektronthermit", the characteristics of this were such as once iniciated it can burn even underwater because it had his own provition of O2. Muzzle speed 695-700 M/s. This variant were used mostly by the maritime and recce aircraft like FW-200C, Ju-88A-14, Ju-290, He-177, Bv-138, etc.

And at last but no at list:

Brandgranate-G-spur.

Completely incendiary ammunition, with tracer, painted entirely in blue. filled with a mix of phosphor and magnesium, 116 grams bullet 710 m/s Muzzle speed. Used with good effect by the night fighters, there was a variant with self-destrution also

 

[CharlesBronson]

All right time to continue here;

Maschinen Kanone MK-101 de 30mm. Part 1

The search for a gun potent enough to face and defeat bombers with few shots gave as result the delopment of the Rheinmetall MK 101 of 30mm calibre. His development began in 1935 ( simultaneously with other weapons) and in 1940 it was ready to large scale production.


Functioning principle:

The working mechanisns in the Mk-101 is one in wich the barrel and bolt recoiled 3 cm backwards afer the shot. The bolt in locked and open for by a locking sleeve, this sleeve have an internal interrupted treads, and is rotated by and milled lugs in the barrel jacket, the sleeve rotation open and closed the chamber. This system was patented by Louis Stange in the late 1920s and used in some Solothurn MGs like the Mg-29, and Mg-30.

In the Mk-101 gave a strong locking system but a slow rate of fire, about 250rpm.

This 30 mm automatic cannon weights (unloaded) 176 kg, had an overall lenght of 2640 mm, is pneumatically triggered and feeded by a ten-round magazines (which could evidently be changed in flight by the gunner).The 30-round drum was introduced in the Hs 129 installation.

In service:

The Mk-101 was first introduced in the heavy fighter Me-110C-6. There was big plans for this fighter and his armament. Almost the entire production of Me-110C-6 went to the special formation Erprobungsgruppe 210, this group had the task to test special weapons and tactics, ( and teorically introduce the Me-210 in front line service) also it participated in the attacks against the radar station and naval transports of Britain coast. The C-6 had his MG-FF guns deleted to save weight. After some successes the disaster struck the Erpbg 210 formation when it lost his commander Walther Rubensdoffer to the Spitfires.


Me-110C-6 with ventral Mk-101.

The same without fairing.

The surviving aircraft wen to some ZG heavy fighter squadrons

 

[twoeagles]

This is terrific stuff, CB - I always get an education on this thread.
Thanks! I know this takes some effort.

 

[CharlesBronson]

This is terrific stuff, CB - I always get an education on this thread.

Oh, Thanks, and yes it take his time to put together all the info, the second part of this tonight.

 

[CharlesBronson]

MK 101 Part 2, Antiarmor usage.

After the withdraw of action of the Epbr 210 and his aircraft in late 1940 this gun was forgotten more than a year by the luftwaffe, nobody know really what to use for.

However the Mk-101 was seriously consider to the antiarmor use after some test in Rechlin in winter 1941-42. The penetration of the of steel AP bullet was pretty average but with the newly designed H-Panzergranate L-spur the Mk-101 probe to be a winner.

Further test was done in the Kummersdorf tank probe facility against some captured tanks. The MK-101 with tugsten core was devastating against the T-34 .
Just 20 % of the bullets fired on the side plate of a KV-1 penetrated, but the effects the top and engine covers were very effective.

Some pics: effect of MK-101 tugsten ammo in KV-1 heavy tank.

Mk-101 in Hs-129B.

The cannon was introduced in the B-1/R3 subvariant and then used in the B-1 B-2 until it was replaced by the MK-103. With the MK 101 the Henschel 129 was rised from a mediocre attack aircraft to a powerful close support plataform.

Squematic MK 101 in Hs-129, note the compressed air bottles for charging.

In Hs-129B-2, in manteinance position

In flight position.

http://i10.tinypic.com/34hj915.jpg