ShVAK vs. MG 151/20

[Finkeren]

Having run down the specifications of the different kinds of aircraft armament, I'm kinda puzzled as to why people are usually refering to the German MG 151/20 as the "best autocannon" in its class from WW2 and vastly superior to Soviet weaponry.

 

On the surface it seems to me, that the two guns are very similar, and it's certainly not a clear cut case in favor of the MG 151.

 

If we take a quick run down:

 

Weight: Exactly equal

 

Rate of fire: Slight advantage to the ShVAK

 

Muzzle velocity: Slight advantage to the ShVAK

 

Effective range: Slight advantage to the MG 151/20 (as if WW2 pilots ever opened fire at 800m)

 

Operation: The unique "bird cage" feed system makes the ShVAK operate extrememly smoothly but jams harder, when something goes wrong.

 

Reliability: Roughly equal, but the ShVAK runs smoother.

 

Durability: Slight advantage to MG 151/20

 

Service life: Advantage to MG 151/20

 

Cartridge: Slight advantage to MG 151/20 in terms of ballistics. Substantial advantage, when using Minengeschoss. 

 

Price/ease of production: Slight advantage to the MG 151/20

 

 

To me it seems like the only substantial advantage the MG 151/20 has, lies in the cartridge it fires, not in the gun itself, and in terms of volume of fire and muzzle velocity it's actually inferior to the ShVAK.

 

Why does the MG 151/20 have the reputation that it does? Am I overlooking something here, or is it just a kind of bias in favor of "German engineering"?

Edited August 20, 2013 by Finkeren

[6S.Manu]

Why does the MG 151/20 have the reputation that it does? Am I overlooking something here, or is it just a kind of bias in favor of "German engineering"?

 

It's bias or ignorance.

 

According to some researches, the MG 151/20 was a little superior to the ShVAK, but of course it was really below the later Hispano: anyway the author ignored some variables who could rank the best German cannon a bit lower (jamming problem) but you know there are no real numbers about that.

http://www.quarry.nildram.co.uk/WW2guneffect.htm

 

PS: IIRC I read in a manual that the "anti-bomber" Fw190s had the cannons' convergence at 1.4Km, while usually that was a 400m.

Edited August 20, 2013 by 6S.Manu

[Finkeren]

I get why you'd call the Hispano superior. It has a slightly smaller volume of fire but much harder punch.

 

The one big problem with the Hispano is the weight of the gun and its ammo. The Typhoon/Tempest was really the only single seat fighter that could truly carry it.

[MiloMorai]

Somehow the Hurricane (4), Spitfire (2/4) and P-51 (4) managed to.

[Finkeren]

Ofc but only with significant modification, and the cannon armed Hurris and early Spits could only carry 60 rounds per gun IIRC, totalling around 5 sec of continous fire.

 

Of course the larger American planes could also carry them with no trouble, sorry for leaving them out.

[Finkeren]

PS: IIRC I read in a manual that the "anti-bomber" Fw190s had the cannons' convergence at 1.4Km, while usually that was a 400m.

1400m seems extreme for a gun with a maximum range around 800m. If you're correct about this it was propably to facilitate shooting at many different distances, by making the guns shoot closer to parallel. I also have a hard time believing, that the Fw pilots would have their sights set to 1400m. At that distance the bullet drop would start to be significant (we are talking 3 - 4 seconds to reach the target) and would screw up aim at closer distances.

[gavagai]

The 4 x Hispano Hurricanes required escort from other fighters.  The negative impact from the heavy armament is something I'm yet to see properly modeled in a combat flight sim, except for the gondola cannon on the Bf 109 (those suck!).

 

Also, the 4 x Hispano A-36 (P-51) is something of a novelty and not representative.  The only American fighter that successfully employed the Hispano was the P-38.  The American copy of the weapon was inferior to the British model and frequently jam when placed in a wing.

 

Anyway, I agree with Finkeren.  The MG 151/20 might be a bit over-rated by flight sim enthusiasts.

[Finkeren]

Well Gav, IIRC apart from the frequent jams due to freezing, weren't the M2-armed F4Us fairly succesful?

[gavagai]

Sorry, I usually forget that one because only 200 were made.

[JtD]

Hispano in Spitfire b wing 60 rpg, later c wing 120 rpg, later e wing 140, Hurricane 90 rpg, and 4 cannon variants did not require escort. Unless used in ground support, where any other plane would usually get ground support, too. F6F used them, F4U did, P-39 did.

 

The ShVAK's projectile is really a bit on the light side, but the Minengeschoss did not have the destructive effect the amount of explosives seems to imply against all targets. It's basically the same thing as thin walled/fragmentation bombs, but on a lower scale. You blow up a bomb in a house, the thin walled might blow it up completely, where the fragmentation bomb will destroy the interior. But if the house is too big, the thin walled will do nothing, where the fragmentation bomb will still destroy the interior, not to mention that the thin walled will be stopped by a good, solid roof, where the fragmentation bomb can still penetrate. It's pretty much the same with the standard HE / Minengeschoss when used against aircraft, each has its own benefits and shortcomings. Usually, in particular against fighter sized targets, the Minengeschoss worked pretty well.

 

Guns jams in US guns were due to tighter tolerances, something the British started with as well, but like the British the US solved the problem eventually.

Edited August 20, 2013 by JtD

[6S.Manu]

1400m seems extreme for a gun with a maximum range around 800m. If you're correct about this it was propably to facilitate shooting at many different distances, by making the guns shoot closer to parallel. I also have a hard time believing, that the Fw pilots would have their sights set to 1400m. At that distance the bullet drop would start to be significant (we are talking 3 - 4 seconds to reach the target) and would screw up aim at closer distances.

 

It was to stay at heavy bomber's six but still outside the tailgunners' range. I'll try to find the document.

Edited August 20, 2013 by 6S.Manu

[6S.Manu]

The 4 x Hispano Hurricanes required escort from other fighters.  The negative impact from the heavy armament is something I'm yet to see properly modeled in a combat flight sim, except for the gondola cannon on the Bf 109 (those suck!).

 

The performance loss was serious; then you know that cannons jam more frequently than a MG and the Spitfire wasn't a really stable platform.  So it was a possible but still "bad" combo.

 

It was better to keep it as an high performance fighter, and use that cannons in a slow but more stable warbird as the hurricane.

 

Yes, the IL2's MkVc(4) was a lame plane... I've scored my first 4 kill streak in that, and it was at the beginning of my training course. With the lack of jamming and the irrealistic stability of that days, you need only to point your "bugged nose" on the target and it was ripped, even at slow speeds.

 

It's no surprising if today in IL2 1946's servers the most flown warbird is the Tempest.

Edited August 20, 2013 by 6S.Manu

[Matt]

This might be of interest.

http://users.telenet.be/Emmanuel.Gustin/fgun/fgun-pe.html

[Finkeren]

It was to stay at heavy bomber's six but still outside the tailgunners' range. I'll try to find the document.

I don't doubt that you have a source for it, but it still seems rather strange to me.

 

1400m is really long range, when talking about aerial gunnery. If we completely disregard the fact, that the stated maximum effective range of the MG 151/20 is just 800m (we're talking about 175% of max range here) it's still a nearly imposible shot to make.

 

A conservative estimate would be, that it takes around 3 seconds for the projectile to cover that distance, it's propably more, but I'll give the idea the benefit of doubt. That means that we're looking at about 45m bullet drop, if we're firing straight and level. So the gun sight would have to be set for that specific range. And the pilot would have to position himself at the exact range, on the dead six of the bomber, which would appear as little more than a thin dark line against the horizon.

 

Even if the FW pilot managed to move is plane into a position at exactly the right range at exactly the same speed and heading and somehow managed to keep his preset sight exactly centered on the tiny B-17 while he gave of a burst of fire from his 4-6 20mm guns, he'd still have to hope, not just that he had calculated the speed and heading of the bomber exactly correct, but that the bomber didn't weer even slightly off course. If, during the three seconds before the burst reached the target, the B-17 were to slide just 0.65 degrees to one side as viewed from the Fw 190, the shot would miss entirely, and it would take an even smaller divergence in altitude to make the entire burst fly right over or under the bomber.

 

1400m is an extremely long range for almost any kind of direct fire. Most snipers in WW2 couldn't hit a target at that range. I have a hard time believing, that Luftwaffe pilots deliberately tried to take pot shots at that range.

[6S.Manu]

I'm trying to find out that document with no result yet, but I can agree with you: my first reaction wasn't different as I read that number.

 

Could it be the crossover distance? Maybe it's only a matter of H harmonization and the pilot would fire at the effective distance?

 

Anyway take my words with a grain of salt by now: it could be that it's not the right number. But it's strange since I used that example to teach my guys during the collimation lesson, so I really think to have read that in the past.

 

It was a technical document about a Fw190 variant IIRC.

Edited August 20, 2013 by 6S.Manu

[6S.Manu]

I'm quite sure it was about the "sturmjager" configuration; because of this there was the two different convergences.

 

Maybe some users have this manual in their library.

[Finkeren]

To facilitate long range shooting, I think it would make most sense to set concergence at maximum effective range. As this would keep a tight grouping at ranges slightly beyond that range but make the weapons that more effective at closer ranges

 

BTW: IIRC the inner pair of MG 151/20s on the Fw 190 weren't set to converge, they just fired straight ahead, didn't they?

[6S.Manu]

BTW: IIRC the inner pair of MG 151/20s on the Fw 190 weren't set to converge, they just fired straight ahead, didn't they?

 

Nope, many Fw190 manuals state that only the machineguns had no crossover (parallel), the inner cannons crossed at 600m and the outer at 800m.

Scribd is full of these manuals.

 

http://www.scribd.com/doc/52929483/1943-D-Luft-T-2190-A-6-Tiel-8A-Fw-190-A-6-Flugzeug-Handbuch-Teil-8A-Schusswaffenanlage-Gilt-auch-fur-Fw-190A-5-U10

http://www.scribd.com/doc/121838098/Focke-Wulf-Fw-190-A-7-R-2-und-A-8-R-2-Bedienungsvorschrift-Schu%C3%9Fwaffenanlage-Rustsatz-2-MK-108-in-den-Flugeln-Mai-1944

 

If only I could find that one about the sturmjager...

Edited August 21, 2013 by 6S.Manu

[Finkeren]

This might be of interest.

http://users.telenet.be/Emmanuel.Gustin/fgun/fgun-pe.html

 

Those were some quite interesting charts. Even though I think the two "quality" values Q and M are determined by some questionable parameters (in both cases the weight of the gun itself is the most important variable) it's interesting to see, that German weaponry generally have mediocre scores.

[MiloMorai]

1400m is an extremely long range for almost any kind of direct fire. Most snipers in WW2 couldn't hit a target at that range. I have a hard time believing, that Luftwaffe pilots deliberately tried to take pot shots at that range.

 

Could be the range for head on attacks, considering the closing speeds.

[gavagai]

Yes, rate of closure was more than 300m/s.  With a muzzle velocity around 700m/s, you can estimate less than 2 seconds for the shells to arrive a target that is 600m closer from when you first squeezed the trigger!

[ImPeRaToR]

Nope, many Fw190 manuals state that only the machineguns had no crossover (parallel), the inner cannons crossed at 600m and the outer at 800m.

Scribd is full of these manuals.

 

http://www.scribd.com/doc/52929483/1943-D-Luft-T-2190-A-6-Tiel-8A-Fw-190-A-6-Flugzeug-Handbuch-Teil-8A-Schusswaffenanlage-Gilt-auch-fur-Fw-190A-5-U10

http://www.scribd.com/doc/121838098/Focke-Wulf-Fw-190-A-7-R-2-und-A-8-R-2-Bedienungsvorschrift-Schu%C3%9Fwaffenanlage-Rustsatz-2-MK-108-in-den-Flugeln-Mai-1944

 

If only I could find that one about the sturmjager...

 

Pretty sure the main user of the R2 versions were the Sturmjäger, and it says the MK108 convergency is at 500m.

 

The first manual states that the cannon shells (20mm) converge with the reflex sight at 125m/550m and 135m/550m respectively.

Edited August 21, 2013 by ImPeRaToR

[6S.Manu]

Pretty sure the main user of the R2 versions were the Sturmjäger, and it says the MK108 convergency is at 500m.

 

The first manual states that the cannon shells (20mm) converge with the reflex sight at 125m/550m and 135m/550m respectively.

 

I know, but it was not a manual like those ones. 

Edited August 21, 2013 by 6S.Manu

[Finkeren]

Yes, rate of closure was more than 300m/s. With a muzzle velocity around 700m/s, you can estimate less than 2 seconds for the shells to arrive a target that is 600m closer from when you first squeezed the trigger!

Let's for a moment ignore, that we've now made the shot even harder by adding the massive deflection that follows from a head on attack into the equation, and focus on the convergence itself. What sense is there to set convergence at 1400, if the distance travelled by the projectile is actually going to be around 800? Unless you mean to say, that they would actually open fire from over 2000m, which seems even more fantastic.

Edited August 21, 2013 by Finkeren

[6S.Manu]

Ehi guys, ignore that number until I find the document. As already said I could be wrong. 

 

Lets stay on topic until that day. 

[Finkeren]

Sure, but in any case it's just a friendly discussion of whether the number is feasible. It's not really a serious point of contention (at least I hope not)

[Gunsmith86]

As far as i know it was never done but it was a idea to use cannons that were capable of fireing from that far away so enamy devensiv fire could not reach the attacking plane. The idea was scrapped  because no gun at this time was fireing fast and far enought to have any chance to hit a bomber that far away (4-5 times with 30mm / 20 times with 20mm from german tests  ) to shot him down. First gun which would have a small chance doing that would have been the MG 213C with a rate of fire of 1200-1400 shots per minute (Cal: 20mm / Muzzle velocity:1065 m/s / Weight: 75 kg / Length: 1.930 mm)  or MK 213C 1100-1200 shots per minute (Cal: 30mm / Muzzle velocity: 530-550 m/s / Weight: 75 kg / Length: 1.630 mm).

[Finkeren]

I can see your point with the MG 213C Gunsmith. That gun at least would have a fair chance of hitting something at 1400m, provided the plane was both precise in its controls and a stable gun platform.

 

On the other hand, I have a hard time seing, what the 30 mm MK could do at that range except waste a lot of ammo very fast. With that muzzle velocity we're looking at a bullet drop greater than the 45 meter

[Gunsmith86]

On the other hand, I have a hard time seing, what the 30 mm MK could do at that range except waste a lot of ammo very fast. With that muzzle velocity we're looking at a bullet drop greater than the 45 meter

 

Thats why they scrapped the idea. The man with this idea must have been someone with not much experience in the field.

 

But if you go close with the Mk 213 C its takes just 3sec of fireing (5% hit rate) to shot down a B-17.

MG 213 C = 5 sec. (5% hit rate)

MK 108 = 5 sec. (5% hit rate)

MG151/20 = 9,81sec  (5% hit rate)

all data is from german tests.

[gavagai]

Let's for a moment ignore, that we've now made the shot even harder by adding the massive deflection that follows from a head on attack into the equation, and focus on the convergence itself. What sense is there to set convergence at 1400, if the distance travelled by the projectile is actually going to be around 800? Unless you mean to say, that they would actually open fire from over 2000m, which seems even more fantastic.

 

I don't know, Finkeren.  Sim pilots seem to want their guns to all converge at an optimal distance where the target will be instantly obliterated.  In reality, many WW2 fighters had their weapons harmonized, i.e. set to attain an optimal spread at a certain distance.

[Finkeren]

I don't know, Finkeren.  Sim pilots seem to want their guns to all converge at an optimal distance where the target will be instantly obliterated.  In reality, many WW2 fighters had their weapons harmonized, i.e. set to attain an optimal spread at a certain distance.

 

The "ideal" spread being a little more than 2/3 of the distance between the outer guns? (Supposing you fire from 800m with convergence set to 1400)

 

I guess the idea of prefering spread over concentration makes some sense, but then why make a system, where the spread is greatest at short distances, where targets should be easier to hit, and have it narrow in with distance, where you supposedly need the spread, like a reverse shotgun?

 

If you want a nice spread at all distances, why not just dispense with convergence altogether and voilá: You always have a nice spread of roughly half a fighter wingspan (at least in case of the Fw 190)

 

Honestly I can't see any rationale for convergence other than the obvious: To obtain the largest concentration of fire at certain ranges. Usually with convergence set a little beyond the distance, where one would usually open fire, since there is a larger toleration for spread at closer distances, where the target appears larger.

Edited August 22, 2013 by Finkeren

[6S.Manu]

From Fw190 vs B-17 (Osprey):

 

 

This in turn meant that the Jagdflieger were often reluctant to press home an attack to close range, opening fire only at extreme, and thus ineffective, distances of around 1,000m.

 

This is the reason I made my opinion about that number. Possibly that document was about this time of conflict.

Also I agree with gavagai about spread: those bombers were big enough.

[ImPeRaToR]

I found these in "Focke-Wulf Fw 190F, G":

 

As it focus primarily on the F and G series I assume the outer cannons on the A series were ommited as they weren't installed when used by Schlachtflieger.

[Finkeren]

Also I agree with gavagai about spread: those bombers were big enough.

But the RLM calculated that it took on average 20 hits to down a B-17, so wouldn't you want concentrated fire rather than the odd single hit?

 

Also, no matter how big the bombers were, there was far, far more empty air between them.

 

The German Flak 18 gunners and especially the fire directors became extremely good at calculating altitude, speed and heading of bomber formations and their shells virtually always exploded inside or very close to the bomber formation, yet they still rarely hit anything but empty air, and it was calculated that it took about 80,000 (eighty thousand) shells to bring down one heavy bomber.

[6S.Manu]

But the RLM calculated that it took on average 20 hits to down a B-17, so wouldn't you want concentrated fire rather than the odd single hit?

 

Also, no matter how big the bombers were, there was far, far more empty air between them.

 

I agree that lower spread could help to score the kill more effectively. Still if we use a "point" harmonization we need to aim well, and to do this we need time. 

 

Now I think in a dangerous environment as this one, pilots could not allow themselves to take their time for the "good" shot with the that risk to be damaged.

 

Its a matter of high-risk/high-reward against the complete opposite.

[Finkeren]

I understand why you'd want to find a middle ground between the need for concentrated fire and the need for fast and easy aiming. Still I'll claim, that the reason you'd bother with convergence in the first place is to concentrate firepower not spread it.

 

In the old IL2, which is the flight sim where I've experimented the most with convergence, my usual distance for opening fire is 50 - 200m, yet I consistently get the best results setting the convergence to 300m. Against heavy bombers I usually set convergence to 600m and open fire from around 500. Now, I understand, that this is a game and does not represent, what would be most effective in real life combat, but it does seem to suggest, that accuracy is genrally best, when convergence is set at a slightly longer distance than you'll usually open fire.

Edited August 22, 2013 by Finkeren

[ImPeRaToR]

In il2 I used 175m and 125m for the inner and outer cannons on the Fw190. In warthunder 150m worked best for me on most planes. 

[Gunsmith86]

But the RLM calculated that it took on average 20 hits to down a B-17, so wouldn't you want concentrated fire rather than the odd single hit?

 

 

 

If you get a view hits on the target there is a good chance that he slow down and lose formation than he is very vulnerable for the next attack.

[6S.Manu]

I understand why you'd want to find a middle ground between the need for concentrated fire and the need for fast and easy aiming. Still I'll claim, that the reason you'd bother with convergence in the first place is to concentrate firepower not spread it.

 

In the old IL2, which is the flight sim where I've experimented the most with convergence, my usual distance for opening fire is 50 - 200m, yet I consistently get the best results setting the convergence to 300m. Against heavy bombers I usually set convergence to 600m and open fire from around 500. Now, I understand, that this is a game and does not represent, what would be most effective in real life combat, but it does seem to suggest, that accuracy is genrally best, when convergence is set at a slightly longer distance than you'll usually open fire.

 

In IL2 1946 you can't change the weapon harmonizations, as they are fixed: so you have an HurricaneMkI who sprays bullets and a P51 with point harmonization who can't damage anything our of convergence. There are situations in which one is more desirable than the other.

 

Then, I can tell by experience in a simulated environment about sturmjager tactics that you aren't able to spend all your ammo without being in danger. If you attack at bomber's six then you are prone to both escort fighters and tailgunners, but instead if you attack by head-on you can't expect to do more than 2 attacks, with limited firing time. After the first head-on you have to chase the bomber stream again, and overtake it to be able plan another attack: this maneuver requires many minutes but flying so close to the stream the escort fighters are going to bounce you (as it happened many times in SEOW campaing, so that Fw190s had to make only to attacks: the first one during the incoming stream and the second one during their route to England).

 

So probably it was better to start firing at very long distance and pray to hit something: still at close range with big target as 4-engined bomber, you could probably still hit something and by head-on it would be probably a sensitive part of the plane.

 

Of course we can only speculate.

Edited August 22, 2013 by 6S.Manu

[VeryOldMan]

Having run down the specifications of the different kinds of aircraft armament, I'm kinda puzzled as to why people are usually refering to the German MG 151/20 as the "best autocannon" in its class from WW2 and vastly superior to Soviet weaponry.

 

On the surface it seems to me, that the two guns are very similar, and it's certainly not a clear cut case in favor of the MG 151.

 

If we take a quick run down:

 

Weight: Exactly equal

 

Rate of fire: Slight advantage to the ShVAK

 

Muzzle velocity: Slight advantage to the ShVAK

 

Effective range: Slight advantage to the MG 151/20 (as if WW2 pilots ever opened fire at 800m)

 

Operation: The unique "bird cage" feed system makes the ShVAK operate extrememly smoothly but jams harder, when something goes wrong.

 

Reliability: Roughly equal, but the ShVAK runs smoother.

 

Durability: Slight advantage to MG 151/20

 

Service life: Advantage to MG 151/20

 

Cartridge: Slight advantage to MG 151/20 in terms of ballistics. Substantial advantage, when using Minengeschoss. 

 

Price/ease of production: Slight advantage to the MG 151/20

 

 

To me it seems like the only substantial advantage the MG 151/20 has, lies in the cartridge it fires, not in the gun itself, and in terms of volume of fire and muzzle velocity it's actually inferior to the ShVAK.

 

Why does the MG 151/20 have the reputation that it does? Am I overlooking something here, or is it just a kind of bias in favor of "German engineering"?

 

 

largest advantage  wa sthe ammunition as  you posted and  the    operational advantages that you cited as small. Production, duirability etc.. those are  HUGELY important isn a long campaign  and are the difference between the gun being there to fire .. and not being  there.

 

That is main reason  US used those .50.  Easy to produce, already mass produced and reliable. That does not win a combat, but wins a war.