Why are the cannons so weak on the 109-E, yet so strong on the Russian planes?

[TRC Subaru]

I have to defend the Devs a little here; one of the best overall fighters is the Spit IX, turns with the La-7 but with more firepower (at least in the game). I really like the La-7 but I always seem to go back in the Spit because it seems to have more “Killing Power” although I believe the La-7 should be stronger then it appears in the game.

I am not a munitions expert but I did dig up some facts after I perceived the La-7’s canons seem to be firing faster then the Spits (and other fighters). The La-7 has some formidable canons (ShVAK, 700–800 rounds/min), that fire faster then the Spits (Hispano, 600–700 rounds/min). Although the muzzle velocity is a bit slower and the shell a bit smaller I believe more rounds per minute (about 100 rounds/min) would seem to give the advantage to the La-7 when compared to the spit and other planes using slower firing cannons. I believe in this regard - More is Better…or Deadlier

Data pulled off Wikipedia:

Armament - Spitfire
• Guns: Mk I, Mk II, Mk VA
o (VA) 8 × .303in (7.7 mm) Browning machine guns, 350 rpg
o (VB on) 2 × 20 mm (0.787-in) Hispano Mk II cannon, 60 rpg (drum magazine); (VC) 120 rpg (belt loaded, box magazine)
o 4 × 0.303 in (7.7 mm) Browning machine guns, 350 rpg
• Bombs:
o 2 × 250 lb (113 kg) bombs

Armament - LA-7• 2 × 20 mm ShVAK cannons; 200 rpg or 3 × 20 mm Berezin B-20 cannons; 100 rpg
• 200 kg (440 lb) of bombs

Specifications Hispano-Suiza HS.404• Type: single-barrel automatic cannon
• Caliber: 20 mm × 110 (0.79 in)
• Operation: gas operated
• Length without muzzle brake: 2.32 m
• Length with muzzle brake: 2.52 m
• Weight without drum magazine: 43 kg
• Weight (complete): 68.7 kg
• Rate of fire: 600–700 rpm
• Muzzle velocity: 840 to 880 m/s (2,750 to 2,900 ft/s)
• Recoil force: 400 kg with muzzle brake
• Amunition: Ball, Incendiary, HE (High Explosive)
• Projectile weight: 130 g HE and HEI 168 g AP-T
• HE and HEI rounds explosive filler: 6–11 g

Specifications ShVAK cannon
• Caliber: 20 mm
• Cartridge: 20×99R
• Rate of fire: 700–800 rounds/min
• Muzzle velocity: 750–790 m/s (2,460-2,592 ft/s)
• Weight: 88 lb (40 kg) without ammunition for the wing version
• Length: 66.1 in (1679 mm) for the wing version

I’m sure there are others out there that are much more knowledgeable and I would welcome more information on the subject.

[Soviet Ace]

So I did some research on the topic last night, and came up with basically what TRC found, but I looked up what the German FF cannon (which should be what the 109E in BoP is armed with), had. Here's what I found.

+ Weight : 26.3 kg
+ Length : 1.37 m
+ Muzzle Velocity : 600 m/s (MG FF), 585 m/s (FF/M with AP or HE), 700 m/s (MG FF/M with mine shell)
+ Rate of Fire : 520 rpm (MG FF, FF/M with AP or HE), 540 rounds per minute (MG FF/M with mine-shot)
+ Round types: armor piercing (AP), high explosive (HE), incendiary, all with or without tracer; high explosive mine-shot (HE(M)) (only MG FF/M)

[winny]

RoF is important but not that important..
It's all about how much weight/HE you can get into a target.

To work it out properly you need projectile weight, % of HE in it and RoF then you could see what the difference would be for a 2-3 second burst..

The Russian projectile weighs 95 grams and is 6% HE.
The British projectile weighs 130 grams and is 8% HE
The German projectile weighs 92 grams and is 22% HE

Russian RoF = 13 RPS = 74g HE per second. (shVAK 20mm)
British RoF = 10 RPS = 104g HE per second. (Hispano MKII)
German RoF = 8 RPS = 161g HE per second. (MG-FF with HE rounds)

Then x that by the number of guns...

(this is ignoring the fact that the spitfire had MG's too)
Muzzle velocity isn't that important (although it does have a significant effect on accuracy).

[TRC Subaru]

Originally Posted by winny

RoF is important but not that important..
It's all about how much weight/HE you can get into a target.

To work it out properly you need projectile weight, % of HE in it and RoF then you could see what the difference would be for a 2-3 second burst..

The Russian projectile weighs 95 grams and is 6% HE.
The British projectile weighs 130 grams and is 8% HE
The German projectile weighs 92 grams and is 22% HE

Russian RoF = 13 RPS = 74g HE per second. (shVAK 20mm)
British RoF = 10 RPS = 104g HE per second. (Hispano MKII)
German RoF = 8 RPS = 161g HE per second. (MG-FF with HE rounds)

Then x that by the number of guns...

(this is ignoring the fact that the spitfire had MG's too)
Muzzle velocity isn't that important (although it does have a significant effect on accuracy).

Great analysis Winny, you clearly are knowledgeable of the subject of ballistics and I agree with your findings, M+V=D, (Mass + Velocity = Destruction…lol)

This formula I believe works very well if you are hitting a stationary object with all the projectiles, but when a moving plane is trying to hit another moving plane, you are often most likely to get a “sweeping” firing line where all the projectiles are not hitting, so with the faster firing gun (la-7), you will get more “hits”. Yes, the gun with higher mass has more “hitting power” but I believe you have enough destructive power with the La-7’s 95 gram projectile and when taking down a plane you need to get a hit in a “critical spot”, motor, fuel tank, etc. so with a higher rate of fire you have a greater chance of hitting a “critical spot” and taking down the plane. In other words, lets just say you have a gun with a 500 gram projectile and only 2 rps as apposed to a gun with a 50 gram projectile and 20 rps, both have the same theoretical destructive power but in a “sweeping fire path” the larger round may miss completely and the lighter round may land several hits, possibly hitting a critical spot and taking down the plane.

Same theory is why a 9mm full auto UZI is more valued in a fire fight then a 44 magnum six-gun. Bigger isn’t always better…

I’m not taking into account what armor the enemy plane has and several other factors, this is just my theory as an engineer, and I’m curious if this made a difference in actual combat, and if “More really is Better”

[Steyr_amr]

[QUOTE=TRC Subaru;140976]M+V=D, (Mass + Velocity = Destruction…lol)

Kinetic energy (Joules) = 0.5 x Mass(kg) x Velocity(metres per second) squared.

This only takes into account inert projectiles though, taking into account HE, AP, actual velocity at which the projectile impacts the target (taking into account range, relative speeds of the aircraft involved, gravity) and whatnot opens up a myriad of mathematics which I'm too tired to be troubled with at the moment.

I don't know much about the specific ballistics, rates of fire and what not of each of the autocannons being discussed here. But although 30mm cannons hit harder their lower muzzle velocity makes fighters much harder to hit with them. The Browning .50 cal was praised for its nice flat trajectory and therefore ease of aiming.

I think i remember reading somewhere also that the MG151/20 as mounted in the 109F was thought much more highly of than the dual MGFF's mounted in Emil due to superior ballistics and a much higher rate of fire. (Personally, I find it much easier to aim just due to it's location in front of the cockpit rather than out on the wing.)

Sorry if this has gone way off topic.

[Panzergranate]

The power of a gun is determined by the length of the barrel in relatition to its bore. This is given as a figure refered to as the Calibre Length, which is given as an "L" number, in cannon ballistics.

For example, a gun described as being 20mm. L55 is 20mm. bore by 20 x 55 millimetres in length.

The bigger the L number the more high velocity the shots fired.

The 0.'50" (12.7mm.) HMGs on the P-51 B are higher velocity than the short barrelled versions on the P-51 D because of the higner velcoity.

Back to the diffences in hitting power between the German and Russian 20mm. cannons..... it is down to gun velocity and ammunition differences.

The German 20mm. cannon is L30 in length/

The Russian 20mm, cannon is L107 in length.

The German 20mm. Solothurn HE cannon shell contains a blue coloured semi-explosive incendary content and isn't particularily large. The AP round, like all AP rounds, is a non-explosive solid manganese steel slug that will punch through steel and thin armour plate found on some aircraft.

The Russian ShVAK fires a much larger shell , with a much larger propelling cartridge down a longer barrel at a higher velocity. The shell is APHE (Armour Piercing High Explosive) designed to penetrate tank armour. It could penetrate around 50mm. of steel and 27mm. of armour plate.

The same goes for the British 20mm. Hispano cannons, long barrelled and high velocity. The Hispano will punch through over 75mm. of steel and 42mm. of armour plate.

The German cannons are underpowered because they actually were in real life.

[philabong2]

hey guys,
all this talk about RoF and fire power reminded me of this vid, I thought this was completly amazing and wanted to share lol - The company's called Metal Storm and are developping new guns which are quite impressive and very versatile - goal is to put maximum amount of effective rounds in the smallest volume and in the shortest time spand

http://www.youtube.com/watch?v=OlkpRjjHaog

There are a few more of these on youtube

[winny]

Originally Posted by Panzergranate

The German 20mm. Solothurn HE cannon shell contains a blue coloured semi-explosive incendary content and isn't particularily large. The AP round, like all AP rounds, is a non-explosive solid manganese steel slug that will punch through steel and thin armour plate found on some aircraft.

The Russian ShVAK fires a much larger shell , with a much larger propelling cartridge down a longer barrel at a higher velocity. The shell is APHE (Armour Piercing High Explosive) designed to penetrate tank armour. It could penetrate around 50mm. of steel and 27mm. of armour plate.

The same goes for the British 20mm. Hispano cannons, long barrelled and high velocity. The Hispano will punch through over 75mm. of steel and 42mm. of armour plate.

The German cannons are underpowered because they actually were in real life.

The shells were not that much different. I've done a diagram.. (to scale)


These are the HE versions
The Germans stopped using AP rounds pretty early in the war because they realised that the high-capacity mine shells (Minengeschoss or M-Geschoss) introduced on the 109 E-4 were far more effective at bringing down aircraft.
(this is the shell that I'm basing my figures on).

The Russian shell was heavier and so was the projectile by a couple of grams, the muzzle velocity of the M-Geschoss was higher than the AP round (585mps) and was 700mps against the Russian 790mps.
The german round contained much more explosive (20g) than the Russian round (6g).

[winny]

It's all a bit complicated..! It probably all comes down to luck. You could put 3 seconds worth through a plane and it survive, or you could hit the pilot with one shot.

Comparing the guns is a little like compring the planes themselves... All have strong and weak points.

I'm no scientist btw, just a bit geeky.

[TRC Subaru]

Good info Steyr, rate of fire must have some influence on hitting a moving object, whether it is a human being or a fighter plane, that is probably why a machine gun was created in the first place, more bullets can make up for a lack of accuracy…as will most likely happen in a moving plane. There may be some differences in rpm, velocity and projectile mass, and with equal pilots in two different planes, one may have a slight advantage, but really, in the end, as Winny says, it may all come down to Luck!