ShVAK vs. MG 151/20

[JtD]

Gunsmith86 - just out of curiosity - what calibre guns do you test?

[Finkeren]

[Gunsmith86]

About 800 cal: .22 lfb

About 250 cal: .17 HMR

50-100 of all other cal from .222 - 8x57 and others

[JtD]

OK, so somewhat smaller than what was suggested by Finkeren. Thanks for the answer.

[EG14_Attila]

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.

Erich Hartmann reached his best results in a distance from 25m to max. 100m! Most the time he used an angle from the "deep" six of the enemy.

[leitmotiv]

in RL that was posible to do, in game in fullreal settings servers large percentage of enemys will notice you creeping on his six from miles away, or in best case from few 100 meters away as from previous expiriance they know they have to check six often, and in most of the times immediately know what he needs to do as he dyed in virtual similar way 1000 or more times and learned what he done wrong last time. There is always few guys you can suprise but they learn fast how to not get suprised next time. Thats why in game players shoot and get used to shoot from far, 300-500m

Edited October 1, 2013 by Yaklover

[Finkeren]

Erich Hartmann reached his best results in a distance from 25m to max. 100m! Most the time he used an angle from the "deep" six of the enemy.

Hartmann flew Bf 109s exclusively and hardly ever used gondola cannons. He wouldn't have bothered with convergence at all.

[EG14_Attila]

Hartmann flew Bf 109s exclusively and hardly ever used gondola cannons. He wouldn't have bothered with convergence at all.

Ooops, you wrote about gondola cannons?! Sorry, I missed this part....

[Crump]

Here is the base weapons set up and convergence for an FW-190A8:

 

 

Here is the FW190A8/R1:

 

 

 

 

[Finkeren]

Ooops, you wrote about gondola cannons?! Sorry, I missed this part....

No, actually it was about the Fw 190.

[Deltrex]

 

 

Comments on Table 2

 

The gun weights quoted above are only nominal and need to be regarded with caution. This is partly because the weights for different guns may not be comparable as various ancillary items may or may not be included; [...]

 

From this:

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

 

I think this all time favorite gun comparison isn't worth all that much, or at lest the effectiveness rating is next to useless. If you want to compare performance per weight you have to include all necessary parts of the gun. If that is not possible than your result will be deeply flawed and the conclusion drawn from it will not reflect the reality.

 

I'm also surprised to see that in all aviation discussions the ShVAK is always the clearly faster firing gun, but when I researched the guns and averaged out the different sources the ShVAK and MG151/20 should have basically the same rate of fire. If you synchronize both guns to fire through the propeller the MG151/20 will even be at a clear advantage regarding rate of fire.

 

Also while the initial muzzle velocity is higher on the ShVAK it will lose its speed more quickly then the MG151 resulting in bullet speeds being equal or even in favor of the MG151 at all but very close ranges.

 

Another factor would be spread, an area where I sadly don't have reliable sources. However the ShVAK has a reputation of being inaccurate at long distances while the MG151 has a reputation of being very accurate at all combat distances. This might however be hearsay and not true at all and since I am from Germany I have to admit that a bit of bias might have influenced the guns reputation here. I would however find it very interesting to get some facts in that area.

[AX2]

From this:

 If you synchronize both guns to fire through the propeller...

A very interesting point...

Some guns or machineguns don´t need be synchronized  with the propeller but others yes.

Some weapons will fire at slower  rate at  low RPMs of the engine ?

Edited October 3, 2013 by Mustang

[Sternjaeger]

Among the other aviation related things I collect, I have quite a nice collection of WW2 aircraft ammunition, it's a really engaging subject with a lot of unexpected twists and technical awesomeness (the picture attached is a selection of the collection).

 

What I've learned to appreciate is that under a ballistics point of view each gun had their drawbacks and advantages (there were also environmental and quality factors, but that's another story..), and in reality there isn't a "perfect gun" as such for aerial combat, the real edge was the pilot and his knowledge of his guns, ammunition and shooting techniques. 

 

It's not a case that the greatest aces of the war were also keen hunters with a long experience in shooting. 

 

As I said, truly fascinating subject, with a lot of surprises as well!

 

SJ

 

P.S.

re. the picture, from left to right:

 

French MAC (7.5mm); ShKas (7.62x54Rmm); early .303 incendiary; late .303 incendiary; Italian Breda-Safat 7.7mm..... and I'll let you guess the rest :-)
 

Edited October 3, 2013 by Sternjaeger

[AX2]

Creat collection ! Thanks For Sharing!

The last is MK 108  ??  ....    ???

I love that ammunition,   "One Shot, One kill"     

Edited October 3, 2013 by Mustang

[Sternjaeger]

yup, the last one is indeed a Mk108, I also have a Mk103, with a much longer case.

[AX2]

Great collection again!

And Mk103 photo ? 

Together Mk 108 ammo and Mk 103 ammo Please !! 

[Sternjaeger]

well since I'm tidying up the man-cave... ;-)

 

here they are: a couple of .50 cals for good measure, 2 Hispano-Suiza 20mm, the Mk108 and the Mk103. The last one is an NS-37, the Russian 37mm cannon round. Unfortunately I don't have a case for this, but I'm looking for one. This would be considerably bigger than the Mk103 as well obviously.

 

[AX2]

Thank you very much  !!! Really ! 

 

well since I'm tidying up the man-cave... ;-)

 

The last one is an NS-37, the Russian 37mm cannon round. 

.....

 

"One Shot, Two Kills"  ...    

Edited October 4, 2013 by Mustang

[Sternjaeger]

definitely, the Russian one is actually an APT, you wouldn't have wanted to be on the receiving end of one of those..

[Sternjaeger]

gentlemen, going back to the topic, please do not forget that these planes flew at altitudes that often required gun heating more than cooling! 

 

The M2 for aircraft use had rheostats that were meant to keep the breech and receiver warm, this in order to avoid the freezing of the grease in it. Many pilots asked, especially with smaller calibres, to tape the muzzle of their guns, so that the cold airflow wouldn't come in until they first used the machine guns. 

 

Another thing to bear in mind is that often the loads for aircraft ammunition were normally "hotter" than the normal counterparts (especially in small calibres): for instance, the 7.62x54R for the ShKas machine gun was loaded with more grains and was absolutely forbidden for use on normal rifles. This was to compensate for the contrary airflow and above all to increase the rate of fire. 

 

All the calibres from 13mm and above also normally had driving bands which diminished the contact surface of the round to the barrel, ensuring a longer barrel life.

 

Once again, each gun had its peculiarities: the Oerlikon cannon for instance was an open bolt design, which was extremely dangerous, especially if faulty ammunition got in the breech.

Edited October 4, 2013 by Sternjaeger

[AX2]

gentlemen, going back to the topic, please do not forget that these planes flew at altitudes that often required gun heating more than cooling! 

 

Good point.

As example,  in  Yaks or BFs the cannons  go through to the engine, then the cannons will be kept warmer ? 

[Crump]

 

altitudes that often required gun heating more than cooling! 

 

 

 

Not when being fired.  The heating was designed to keep the breech from icing so the gun could fire in the first place.

 

The manual is quite clear on the M2 firing limits and it is not in error.

[Sternjaeger]

I don't know whether the rheostats would cut off at a certain temperature or when being fired, but bear in mind that firing was just a very small fraction of time and never done in bursts longer than 10 secs, so I doubt overheating was a problem at any time, and again not only because of the air that was rammed in, but also because temperatures easily reached negative double digits pretty fast as they climbed.

 

The Germans learned from the Russians to completely strip their guns clean of any lubricant with petrol in order to avoid them to freeze in the first place, but you can imagine that the wear on the moving parts of those guns was considerably higher than normal.

 

New replacement barrels soon became a desirable but discontinued commodity, especially on the Eastern Front.

[Crump]

 

I don't know whether the rheostats would cut off at a certain temperature or when being fired

 

The heater system on most was manually controlled.  All it does is divert heated air from the exhaust to the weapons bay.  Same thing as cabin heat on most aircraft.

 

 

 I doubt overheating was a problem at any time

 

 

Only when being fired....

 

Bottom line, the manual is not wrong.

 

Machine guns have three rates of fire.

 

1.  sustained rate of fire - The rate of fire used in normal combat operations and the gun is designed to be operated at continuously. 

 

 

What is the sustained rate of fire for the M240B?

100 Rounds per minute fired in 6 to 9 round bursts and 4 to 5 seconds between bursts. Barrel change every 10 minutes.

 

 

Rapid rate of fire is for emergencies, things like FPL (Final Protective Lines)....

 

 

What is the rapid rate of fire for the M240B?

200 Rounds per minute fired in 10 to 13 round bursts and 2 to 3 seconds between bursts. Barrel change every 2 minutes.

 

 

http://www.armystudyguide.com/content/army_board_study_guide_topics/m240b/m240b-study-guide.shtml

 

You can see these limitations are very close to the M2 MGAW:

 

 

Cyclic Rate of Fire is the mechanical limits and assumes unlimited supply of ammunition and no malfunctions.  Count yourself lucky to get a machine gun thru a minute of cyclic rate without a malfunction assuming you have a belt or hopper big enough.

 

This whole discussion has gone to the realm of the surreal.

 

The manufacturer, end user, and engineers wrote the manual.  It is correct and how the weapon was operated in combat.  There was no combat fairy that changed the laws of physics.

Edited October 5, 2013 by Crump

[Sternjaeger]

Crump, I'm afraid you are getting a bit confused:

 

1) the gun heating was also often electrical (especially on wing guns) and provided by specially designed mounts that sat on the gun. Have a look here: http://www.bmgparts.com/aircraft.html

 

2) overheating on aircraft guns has never been an issue, because pilots didn't shoot long bursts and because of the environmental conditions.

 

3) jams were averted by better ammunition design (the .50 and .30 cal design improvements became widespread across all producers, so they could be interchanged), but there were some early design flaws (i.e. on early Mustangs).

Some guns (i.e. the MG151/20) had buttons which allowed to unjam the gun by means of an electric motor.

 

4) rates of fires were controlled either by sync mechanism or by the kind of ammunition. Armourers could adjust this marginally by regulating recoil springs,

Edited October 5, 2013 by Sternjaeger

[Crump]

 

Crump, I'm afraid you are getting a bit confused:

 

 

 

Not confused about a thing.

 

 

 gun heating was also often electrical

 

 

Yes, hence the phrase "on most aircraft" which is not "all aircraft"!     Check out the heating system on the FW-190 for example.  Aircraft engines produce a lot of waste heat especially turbines of today.

 

 

 

overheating on aircraft guns has never been an issue, because pilots didn't shoot long bursts

 

 

Right.....glad this is recognized.

 

They followed the training there were given and the instructions on proper operation of the weapons.

 

 

 jams were averted by better ammunition design (the .50 and .30 cal design improvements became widespread across all producers, so they could be interchanged), but there were some early design flaws (i.e. on early Mustangs).

Some guns (i.e. the MG151/20) had buttons which allowed to unjam the gun by means of an electric motor.

 

 

 

Yes, in addition to pilots properly operating the guns as they were trained to do, the engineers found ways to improve reliability too.

 

 

 rates of fires were controlled either by sync mechanism or by the kind of ammunition. Armourers could adjust this marginally by regulating recoil springs,          

 

 

Which is why most gun specification list cyclic as a range. 

 

This fact does not have anything to do with the operator using proper sustained or rapid rate of fire in an emergency.

[Sternjaeger]

Yep, but it still remains that even in cases where they needed to use all of their ammo in one burst (which is virtually useless), the issue of overheating would have never occurred, probably not even in tropical or desert scenarios.

 

..I might have missed the main point here, but what was the original disagreement about? 

[79_vRAF_Friendly_flyer]

I have read some accounts of Hurricane pilots firing very long bursts in the first year of the war, trying to take down bombers with MGs only. This is perhaps the only situation where heat-wear would be an issue. As they rearmed with auto canons, the need for long bursts diminished.

[Sternjaeger]

Sure, but we're still talking about 20/30 seconds in total? Hardly anything for a .303 barrel, even if they used lightened ones.

[ACG_Dickie]

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.

 

No, it was because they modified them, against British advice.  A successful weapon, deployed in the field, held back from deployment by tighter tolerances?  The only reason I can think of for that is US politics, since the US made Browning was used instead of the Hispano - I can believe that,  but it wasn't because there was anything wrong with the gun.

Sure, but we're still talking about 20/30 seconds in total? Hardly anything for a .303 barrel, even if they used lightened ones.

 

There was only 15 seconds of ammo in the Spits and Hurricanes.  250-400 rpg.

[Sternjaeger]

No, it was because they modified them, against British advice.  A successful weapon, deployed in the field, held back from deployment by tighter tolerances?  The only reason I can think of for that is US politics, since the US made Browning was used instead of the Hispano - I can believe that,  but it wasn't because there was anything wrong with the gun.

 

There was only 15 seconds of ammo in the Spits and Hurricanes.  250-400 rpg.

 

as far as I know gun jams in the US forces (when it comes to aircraft) were mainly due to either to design flaws (i.e. the angled installation of M2s in early Mustangs which caused repeated jams), the standard of US ammunition was extremely high and above all the design of the ammunition itself was extremely simple and dependable.

 

Complicated ammunition and production methods (let's not forget that a lot of German ammunition was produced by POWs) give you a higher chance of failures: to give you an idea, an MG151/20 HE round is made of circa 20 single components (several of which were machined and had to be assembled by hand), whilst an M2 round is made of 4, and production was automated.

 

 

Thanks for the clarification on the seconds of fire, 15 secs is even less of a concern for barrels then!

Edited October 7, 2013 by Sternjaeger

[JG1_Pragr]

In one of many editions of Pierre Clostermann's The big show, there is appendix containing several of his combat reports. They are listed with the ammunition usage. I was really surprised how many times he experienced the gun or cannon stoppages. They were more rule than exceptions.

[Sternjaeger]

yep, but in that case we're talking about the Hispano Suiza cannon, which was an awfully unreliable and dangerous gun because of the open bolt design and because the belt links made feeding even more problematic. Together with that is the fact that Clostermann probably did a lot of high G dive recoveries after ground strafings, and this was a further cause of jamming.

The open bolt design of the gun itself was extremely dangerous: there have been several cases of aircraft being damaged by rounds exploding before being fully chambered and making a glorious mess of the wing (if not detaching it!).

It is no wonder that soon after the war the design was dropped in favour of other more reliable guns, whilst the MG151/20 (an intrinsically safer and more reliable design) was extensively used after the war by the French Army and Air Force.

Edited October 7, 2013 by Sternjaeger

[JtD]

No, it was because they modified them, against British advice.  A successful weapon, deployed in the field, held back from deployment by tighter tolerances?  The only reason I can think of for that is US politics, since the US made Browning was used instead of the Hispano - I can believe that,  but it wasn't because there was anything wrong with the gun.

From the top of my head, so no warranty I got the details right: The British initially also had problems with jams in the Hispano, which was was reduced to an acceptable degree by giving the feed mechanism/chamber/case ejector a little bit more play/clearance. This then went to the US, where they figured that the extra mm or so was a too excessive tolerance, got rid of it, and with everything neat and well fitting, went right back to where the British had started.

[Sternjaeger]

as far as I know the problems the RAF had were related to guns freezing, they relied on the open bolt mechanism to keep the cannon from jamming, but they soon were proven wrong. There was a minor change in the case shape, but in general you need to keep the mechanism and tolerances pretty tight, especially on open bolts. The main modification the American made was a slight redesign of the case neck, and after the war the US Navy made a newer version of the 20x110mm, with a case section that was slightly conical instead of cylindrical (which helped reducing tolerances even more). 

[Sternjaeger]

 

some examples here, from L to R, the 20x110 US Navy (postwar, note the conic shape of the case) the rest are all 20x110 HS apart for the last one, which is an Oerlikon.

Edited October 7, 2013 by Sternjaeger

[79_vRAF_Friendly_flyer]

as far as I know gun jams in the US forces (when it comes to aircraft) were mainly due to either to design flaws (i.e. the angled installation of M2s in early Mustangs which caused repeated jams), the standard of US ammunition was extremely high and above all the design of the ammunition itself was extremely simple and dependable.

 

According to Lieutenant Colonel Chinn, USMC, who wrote a rather thorough report (five volumes) for the Navy Ordnance Dept. in 1951, the reason was that the US engineers insisted on having a slightly longer chamber than the original British one, about 2 mm in difference:

 

Chinn (p 578), comparing American and British made guns:

 

The main difference in the two types of gun was in the chamber dimensions. Since both were designed to use the same cartridge, it was quite obvious that one size would best handle the round. The British were very insistent that their measurements were better, pointing out, in particular, that their chamber was slightly more than one-sixteenth inch shorter than the American one. In their opinion, such a length would solve the problem of faint strikes, since the weapon was inertia fired and depended upon the shoulder of the chamber to offer resistance and position the cartridge.

 

and

 

Oddly enough, the question was again raised, not by the English or our many proving grounds, but by manufacturers of 20-mm ammunition. In testing their cartridges for reliability of action, they encountered a series of malfunctions known as light-struck primers that were all out of proportion for such a weapon. These were not isolated cases, the reports coming in from practically every maker of 20-mm ammunition that was engaged in function firing his products.

 

To avoid retooling under wartime considerations or pigheadedness (or both), the US Hispanos were never corrected, leaving the USN and USAF with .50 M2s as the only available choice for fighter armament (the American Hispano guns were mainly used in the AAA role). In the end, the US solved the problem by switching to electrical priming for their long chambered Hispanos, but by the time this became available, the war was over.

 

For some extremely frustrating reading on the development of the American Hispano, see

 

Chinn, George M. (1951). The Machine Gun: History, Evolution, and Development of Manual, Automatic, and Airborne Repeating Weapons. Washington, D.C.: U.S. Government Printing Office. Scroll down to read pages 562 to 590.

[JtD]

Thanks for this. Remembered it the wrong way round. :o

[Sternjaeger]

[...]

 

To avoid retooling under wartime considerations or pigheadedness (or both), the US Hispanos were never corrected, leaving the USN and USAF with .50 M2s as the only available choice for fighter armament (the American Hispano guns were mainly used in the AAA role). In the end, the US solved the problem by switching to electrical priming for their long chambered Hispanos, but by the time this became available, the war was over.

 

[...]

 

I'm sorry but this is not entirely correct: the US-licensed version of the Hispano-Suiza was indeed used both by the Army and Navy, on the P-400, P-38, P-61, B-29, F4U-1C and F6F-5N. The 20mm used as AAA was the Oerlikon, which used similar bullets but different casings. 

The switching to electric priming and the adoption of a different case was the next step done by the Navy, which was then substituted by the 20mm Vulcan. 

Edited October 8, 2013 by Sternjaeger

[VeryOldMan]

I can see the heatign problem beign VERY relevent on  the  defensive weaponry on  Flyign fortresses.  THose would likely  fire way mroe than a fighter gun would when the pilot was  much more worried on keeping that Fw190 away of his bird  than on keeping his gun  on a long life.