Luftwaffe Cannons and Machineguns topic.

I would consider the MK 108 as poor defensive wepaon - the poor ballistics make this a very short ranged weapon. As defensive gun you want something with range and good ballistics so you would be able to hit something attacking you while still at a distance.

Additionally, the Mk108 had a low rate of fire due to it's design.

The MG151/20 would have probably been a better choice...

Duplicate post...

Does anyone have any information on the dates various types of ammunition were introduced into service?

Except the rifle ammunition, I imagine this was all in use from the beginning of the war.

Greyman said:

Does anyone have any information on the dates various types of ammunition were introduced into service?

Except the rifle ammunition, I imagine this was all in use from the beginning of the war.

Click to expand...

The information in on this topic, some photos are no more though.

Update on the MG C30/L cannon

New information and photos has emerged on this short production weapon. he MG c30/l caliber 20x138b was a Swiss Solothurn design for and army support and light Flak gun. The weapon was originally box magazine fed with 20 rounds, for aircraft use a 60 rounds (some sources say 100 rounds, but the size in photograps doestlook like a 100 rds to me)
Short recoil operated with intermediate locking ring, rate of fire was 300-340 rpm. Basically a Rheinmetall Borsig Flak 30 adapted to fighter use.
2 images of the Erhardt-Solothurn MG C30 / L (also know as MG 102) notice the large drum magazine for the 20x138b ammo below the action, a weird location because most guns of the had it in the side or on the top position.



The only know operational use of this large gun was in the ground strafer/antitank experimental plane Heinkel 112 V6 as "motorkanone", that means firing through the propeller hub. German pilots of the J88 fighting in Spain in 1937 use alternatively this plane to He-51biplane.The pilots claimed 3 T-26 tanks and 2 armored trains destroyed, wich is not a surprize because the large muzzle velocity of 860mps.
Later in 1940 many were adapted fof air defense role in the Atlantic wall.

Any confirmation that this actually true?

Dornier Do 335 by Karl-Heinz Regnat (Schiffer 2003) page 132.

The data is reproduced from the (original) Dornier Do 335 technical description manual pertaining to the Mk 103, to wit:

"One MK 103 in Mol 103/1A engine mount in forward engine, firing through the hollow propeller shaft. Rate of fire: sixty-five rounds per minute."

The Do 335 only carried 70 rounds (possibly 65 rounds) (between Frames 1 and 2) for the MK 103. Unregulated the MK 103 would run at 380 r/m when firing HE/AP tracer, and at 420 r/m when firing Mine shells. 70 rounds at 380 r/m will give you 11-seconds of trigger time. 70 rounds at 420 r/m will give you 10-seconds. Factoring in the inherent inaccuracy of the weapon: "With a firing probability of 95%, it was calculated that 76 rounds would have to be fired from a range of 500 meters to achieve three hits on target. This figure rose to 203 rounds from 1,000 meters and 650 rounds from 1,500 meters," it was statistically impossible to hit anything at 380/420 r/m outside of 500 meters.

The Luftwaffe regulated the MK 103's rate of fire down to 65 r/m to improve it's statistical ability (not actual ability) to put rounds on target.

Milosh said:

Any confirmation that this actually true?

Dornier Do 335 by Karl-Heinz Regnat (Schiffer 2003) page 132.

The data is reproduced from the (original) Dornier Do 335 technical description manual pertaining to the Mk 103, to wit:

"One MK 103 in Mol 103/1A engine mount in forward engine, firing through the hollow propeller shaft. Rate of fire: sixty-five rounds per minute."

The Do 335 only carried 70 rounds (possibly 65 rounds) (between Frames 1 and 2) for the MK 103. Unregulated the MK 103 would run at 380 r/m when firing HE/AP tracer, and at 420 r/m when firing Mine shells. 70 rounds at 380 r/m will give you 11-seconds of trigger time. 70 rounds at 420 r/m will give you 10-seconds. Factoring in the inherent inaccuracy of the weapon: "With a firing probability of 95%, it was calculated that 76 rounds would have to be fired from a range of 500 meters to achieve three hits on target. This figure rose to 203 rounds from 1,000 meters and 650 rounds from 1,500 meters," it was statistically impossible to hit anything at 380/420 r/m outside of 500 meters.

The Luftwaffe regulated the MK 103's rate of fire down to 65 r/m to improve it's statistical ability (not actual ability) to put rounds on target.

Click to expand...

The 65 rpm rate of fire in WRONG,the correct rate of fire of that gun was between 360 to 420 rpm. A semiautomatic gun could fire at more than 65 rpm, make no sence whatsoever.

GrauGeist said:

Additionally, the Mk108 had a low rate of fire due to it's design.

The MG151/20 would have probably been a better choice...

Click to expand...

For the caliber (and projectile weight) involved, the MK108 was light and fast firing for the time, just low velocity, rather like other low velocity API blowback designs (MG FF and various Oerlikon FF all the way back to the WWI Becker cannon the Oerlikons were in turn derived from) with the exception that the MK 108 was also engineered specifically to be cheap and fast to manufacture, optimizing the number of stamped steel parts.

I have wondered if necking the barrel down (sort of the opposite of the MG 151 to MG 151/20 conversion) to a smaller, lighter caliber (like 23-27 mm) for higher velocity would have been a better compromise for most applications. Though even simpler than that would have been just lengthening the cartridge case and shortening the shell length (lighter projectile and heavier powder charge) likely with an increased minimum barrel length. The problem there, at least for increased powder charge, would be exceeding the structural limits of the gun. (reducing projectile weight does tend to reduce chamber pressures on its own, so some increase in powder should have been possible, while longer barrel would just be needed to allow more complete expansion of the propellant -not that big an issue given most aircraft used barrel extensions to clear their cowls anyway -the basic MK 108 barrel being extremely short) Keeping the same caliber and overall ammunition dimensions would allow the basic gun mechanism and barrel design to remain unchanged while also using the same fuzes and higher capacity filler than smaller (even longer) caliber necked-down variants.

Lighter projectiles would have worse ballistic performance due to lower sectional density, but the higher velocity would still make time to target and trajectory a lot better, and increasing practical ranges if not maximum range.



Edit:
In terms of effectiveness of defensive armaments, I'd think the 15 mm MG 151 would be superior to the 151/20 in that respect due to the better velocity and ballistics coupled with the suitability of the lighter 15 mm rounds against most enemy fighters. (the lower weight of the 15 mm barrel might have made some flexible mountings easier as well, of course proper powered turret mountings would be needed to be really effective)

The main problem with trying to soup up the MK 108 was that it was a very careful balancing act between the shell leaving the barrel and the case coming out of the chamber. The short barrel and small powder charge meant the shell cleared the barrel and allowed the pressure in the chamber/barrel to drop sharply before the breechblock had moved very far and exposed unsupported cartridge case wall to open air. (this is true for most blow back guns and is the reason for their rather low rates of fire, more chamber time). Increasing pressure or increasing the time before the shell leaves the barrel is going to require lowering the rate of fire or much stronger cartridge cases. A ruptured cartridge case letting high pressure gas back into the action will pretty much wreck the gun.

You also have to be careful about using really light shells to try for high velocity as the German 20mm mine shells already had longer times of flight to long ranges (500-600meters) than the conventional shells that started out almost 100m/s slower. Yes they offered shorter times of flight at short ranges but the "slower" shells caught up well before 600 meters was reached.
Germans did improve things with more pointed 30mm shells (more streamline) which retained velocity better but I don't know how many got into the supply chain. The 30mm shells had a pretty poor shape so that looks like a better bet for improvement than playing jiggery-pokery with shell sizes and weights.

Those are some of the reasons behind my comment on powder charge increases and structural limitations.

However, that situation is at its worst for powder charge increase with projectile weight staying the same. With a powder charge increase AND significant reduction in projectile weight, the acceleration will be much greater and will thus exit a longer barrel more quickly. (finding the useful compromise between increased powder charge and decreased projectile weight would be the trick here, while avoiding modifying the gun mechanism itself if possible) A shorter, lighter projectile with the existing powder charge would also improve velocity somewhat, but increasing the powder charge somewhat should still be possible.

I believe necking the casing down to a smaller caliber might also introduce more problems with pressure for any given powder load and barrel length, and seems less attractive than changing the case length to shell length ratio (with overall cartridge dimensions remaining unchanged).

The improved ballistic shape appears to have been exclusive to the HE/HEI tracer rounds (which also appear to be the only tracer rounds implemented for the cannon). Given the need for tracers for pretty much any operation, that streamlined shell may have been available early on, but the bulkier counterparts may have been produced alongside it due to cheaper/simpler construction (of both shell casing and fuze), and the somewhat higher filler capacity. (the compact fuze used in the more streamlined nose may have been more costly to manufacture than the ones used in the bulkier non-tracer ammunition, though I suppose another compromise would be reducing the shell length further, reducing the filler somewhat, and adding an aerodynamic extension cap ahead of that standard sized fuze)

The early mine granate was employed simply to increase the HE charge in a more easy to manufacture explosive round, the Luftwaffe technicians were aware of the limitations against armor and its aerodinami drag but you got to compromise, specially when you hav not abundant raw materials like in the german case. The design was improved for the 30mm aniway.

For the difference just changing the shape of the nose can make see this:

round.....................MV in M/s......V at 300m........Time to 300m in sec......V at 600m.......Time to 600m ""


13mm HEI 34gr.........750...............501...................0.49..........................337.....................1.22
20mm HEI 92 gr........695...............432...................0.551........................281.....................1.428 (1)
20mm HET 117gr.......720..............552....................0.447.......................422.....................1.101 (2)
30mm HEI 330gr........500..............370....................0.696.......................264.....................1.660 (3)
30mm HEI 330gr........500..............429....................0.649.......................370.....................1.403 (4)

The difference in the 30mm ammo was just the change in shape of the nose.
The difference in the 20mm ammo is that the 92gram mine shell was fired by the MG/FFM and the 117gram shell was fired by a MG 151. Please note that the light weight shell lost 55m/s in velocity more than the heavier shell by the time it got to 300 meters and had lost 116m/s more than the heavy shell by the time it reached 600 meters. Using short, light shells may work at short ranges but just makes things worse at long ranges.

CharlesBronson said:

The early mine granate was employed simply to increase the HE charge in a more easy to manufacture explosive round, the Luftwaffe technicians were aware of the limitations against armor and its aerodinami drag but you got to compromise, specially when you hav not abundant raw materials like in the german case. The design was improved for the 30mm aniway.

Click to expand...

That's relevant to the 20 mm mine shells, but not 30 mm.

The context here is:
Komet weapons: MK 108 cannon

this:
https://robdebie.home.xs4all.nl/me163/images/large/weapon26.jpg
Type I, German name: 3 cm Minengeschoss 108 Ausführung A mit Zerleger

vs
https://robdebie.home.xs4all.nl/me163/images/large/weapon27.jpg
Type N, German name: 3 cm Minengeschoss Leuchtspur mit Zerleger (day tracer) / 3 cm Minengeschoss Glimmspur mit Zerleger (night tracer)


The latter also being the only tracer round used with the MK-108. With the better ballistic shape, self-destruct mechanism, and tracer, it really seems like using that shell exclusively would make the most sense. (unless the draggier non-tracer versions were that much cheaper to make -plus the thermite incendiary version was not implemented in tracer form)

The 20 mm shells used normal (none-minengeschoss) shells for tracer and AP rounds, the MK-108 generally avoided bothering with AP rounds (experimental ones aside) and used just the minengeschoss.





And thanks for those figures, Shortround, really nice info there. The non-streamlined 30 mm shell seems particularly poor in this context, as it drops subsonic somewhere between the 300 and 600 m range (barely supersonic at 300 m really) and stability oscillations in the transsonic range are pretty nasty. The streamlined shell is supersonic out to 600 m (or a bit beyond) so while trajectory would dip a lot, it should at least be stable in flight. (and still dip a lot less than the draggier round, or the 20 mm mineshell)

That said, the velocity on the 20 mm shell seems pretty low, or possibly for the MG FF/M rather than 151/20. (though I usually see 104 or 105 g listed for those shell weights, but I suppose 92 g might be a later variant with even thinner walls and a higher portion of -relatively lightweight- filler)

And that said, you'd have a fairly long way to go in dropping 30 mm size to the same sectional density of that 92 g shell. 30 mm presents 2.25x the area of 20 mm, so 92 g 20 mm would be equivalent in sectional density to a 207 g 30 mm shell. (which, with the same muzzle energy of a 540 m/s 330 g shell, should manage 682 m/s -but internal ballistics don't quite work linearly like that most of the time, so it might be higher or lower with the same powder charge ... though I'd think something in the 270 g range would be a better compromise, along with whatever increase in charge could be tolerated by the gun)

And to use the 500 m/s MV from your example, a 207g shell of the same muzzle energy would be 631 m/s.

The 'mine shell' for the MG FFM and MG 151/20 was at 92 g, ie. both guns fired the same shell, obviously the 151/20 fired at higher MV due to bigger propellant charge.
The bigger type of 20 mm mine shell, 'MX' was heavier and used only by the MG 151/20, late in ww2.

A few points I've learned more on in regards to both gun and cartridge design:

Case area is important in controlling case pressures and stresses tolerated both by the case walls and by the primer cavity. (too much pressure will blow out the primer and damage the firing pin)

Additionally, lighter projectiles will accelerate faster and /somewhat/ reduce case pressure, but this also depends on the powder burn rate. (extremely fast burning powder will create a sharp pressure wave regardless)

The point made about extending the barrel length of the MK 108 (without significantly changing the mechanism of the gun itself) is the strongest limiting factor in all this, and a very good point. Changing the barrel length would create all sorts of problems, including inability to use standard MK 108 ammunition.


So, with that in mind, the alternatives would be:
Keep the overall length of the cartridge the same while extending the case, shortening the projectile and stretching the case and increasing the powder charge to the point of matching recoil/blowback properties for reliably operating the mechanism. (this is not a simple matter of matching muzzle energy as you typically need /more/ muzzle energy to match recoil forces of heavy rounds using light rounds at increased velocity; with gas operated weapons, this isn't a factor at all, but for recoil and blowback ones, it has a major impact on reliability)

Extraction of longer cases might be a problem, but up to a point, may function without any modifications there either (possibly more of an issue for external ejection chutes in specific aircraft).

Obviously, the superior ballistic shape should be retained for a shell of any length. (and indeed, is what post-war British 30 mm ammunition opted for)

Hi,
Thought this would be appropriate to this thread
Bobby

Never seen a photo of this one.
OERLIKON/302 RK/NR. 109. Barrel adapter: 5.

Notes: "The story of the revolver cannon beings in England in 1718 with Mr. James Puckle. The device...had one especially interesting feature; it anticipated the requirement for two different ammunitions to be fired from the same gun. Mr. Puckle suggested in the patent that the cannon be loaded with square bullets for infidel and round bullets for Christians.
The next historical occurence of the revolver cannon came in 1861. The DeBrame cannon was interesting in the sense that the basic layout and components exactly duplicated the modern revolver cannon. Mr. DeBrame's gun was not automatic loading and had to have the rounds both loaded and extracted by hand, however, the breeching mechanism did not provide a model for later efforts.
The first gas operated revolver cannon came into the United States in 1905. This era was the heyday of machine gun inventors and everyone who fancied himself a gun inventor had invented at least one machine gun. The Clarke gun used the same principles used today in that the cylinder was rotated by a gas operating slide. The gas for the operation being tapped off the barrel in a way used many, many times since.
The recent history of the revolver cannon began in Germany in World War II. The German high command developed a requirement for a 'million point gun,' that is, a thousand shot per minute with a velocity of a thousand meters per second to arm the ME262 airplane. It was recognized even then that jets with their higher closing speeds were going to need a high rate gun to provide optimum kill capabilities, so the 1,000 rpm requirement was set for this aircraft. The sporting arms firm of Krieghoff had such a gun in 20mm which was known as the MG-301. The German high command, at the insistence of World War I ace, Ernst Udet, felt the Krieghoff firm had neither the facilities nor the background to develop an aircraft cannon and moved the development to Mauser, where the gun was renumbered MG213-A. This gun was not a revolver cannon; it was a reciprocating type gun. The MG213A design was passed on to the designers in the Mauser design group. It's interesting from the standpoint of what has happened to later revolver cannon developments to look at the makeup of this group. The two principal designers associated with the project were Mr. A. Politzer and Mr. Werner Jungemann. As in any design group, it is quite clear that while these people may have been the principals, there were many, many others behind them. As a result, many different people could be called the designers of the modern revovler cannon. The Project Engineer was Mr. Linder and the Joint Managing Director was none other than Otto Von Lossnitzer.
The 213A would not come up to rate although the ammunition performance was quite impressive, so Mr. Linder proposed a variation (still a reciprocating gun) called the MG213B. Some analysis was done on this and it was decided that the gun still would not achieve the required rate. At that point the revolver cannon design, which was identified as Mr. Politzer's version and the MG213C, was proposed. The 213C showed sufficient promises so that development began first in design and then in hardware. A prototype gun and five others were built at Mauser.
To really understand the operating principle of a revolver cannon, it's probably easiest to compare the cannon to an ordinary revolver pistol. In the revolver pistol, for basic components are required; a barrel, a frame to support the barrel and provide a locking surface behind the revolver, the revolver cylinder itself, and a means of rotating the revolver cylinder after each shot. With the revolver cannon these same elements are present, the barrel, frame, and revolver cylinder. The mechanism for rotating the revolver cylinder changes to an operating slide which is driven by a gas piston obtaining its energy from a gas tap in the barrel. Two other features are added - a rammer and After the war the design group at Mauser was faced with the prospect of being captured either by the Western powers or by the Russians. The designers involved in the 213 group all opted to be 'captured' by the West. Werner Jungemann went to England in 1949 taking with him some MG-213C drawings which were converted to English dimensions most nearly like Mk 213/30. The version became the Aden Gun. Anton Politzer went to DEFA in 1948, hired 40 to 50 people to form the DEFA revolver cannon design group. The success of the effort is still visible today. Frederick Linder moved to Oerlikon in 1947 where he began work on the 302RK, a follow-on generation to the 302. The 304 differed from the 302 in two important respects; one was that the cradle was eliminated and the entire gun except for the mounting flange was to allow to recoil. The gun was also lighened and made more compact by reducing the revolver cylinder in four chambers instead of five.
To complete the post-war picture. Otto went to Springfield in 1947 where a captured 213C, rebuilt by the Naval gun factory, was renumbered T-74. The T-74 progressed in 20mm through the T-110 and the T-160 which was type classified as the M-39. There were also several 30mm version of he MG-213C-type gun studied and built at Springfield in the same time period." Chinn

Something I've stumbled across - a table comparing the current German cannons in early 1945. I understand the "number of hits required" as applying to the assured destruction of a 4-engined bomber. The 'quality factor' should be the weight of shells thrown in a period of time (second? minute) divided by gun or cannonn weight. Translation by your's truly.

Nice Tomo and thanks