20mm cannon, best, worst, specs, comparison to LMG, HMG etc.

[Aozora]

That is a generalization not born out by combat. Shredding the skin basically doe snot bring plane down, a critical system or several less critical systems must be damaged/destroyed. The 20mm could not destroy an engine in one shot a .50 cal can, same with armor plate (typically). Any system hit by a .50 is at least severely damaged is had too much penetration. I have seen many gun cameras of many German fighters using 20mm and the plane they shot would at first lose sheet metal. It generally took a several shots before they finally found a soft spot to damage the plane enough to down it. When gun camera from US fighters were compared in the east once an SAPI round hit the fuel tank they always burned, a 20mm HE does not start fire like that. Against the Germans, IHMO the .50 cal fired until the engine quit, the pilot was killed, or the fuel tank flamed.

Still waiting for your evidence for these claims...

 

[Jabberwocky]

The Germans quickly switched to essentially only Mingeshoss, thins walled HE

No, they didn't. You clearly have done NO research and you have NO idea what you're talking about.

Standard fighter belting for the MG151/20 from 1942 onwards was 2 M'gschoss, 2 high explosive incendiary and either 1 or 2 AP HE or one API. Anti-bomber configurations had more M'gschoss, Eastern Front configurations had more AP, give the presence of the Il-2.

Not sure what why you are basing any comments on less than 5% of the ammo and gun type that caused fighter combat losses. What about the other 95%

Non-sequitur?

You do realize the Navy did not accept the HS as is was unsuitable and spent over 15 years making changes to it and the ammo until it was.

Again, you have NO idea what you're talking about. The Hispano was perfectly acceptable to the USN, once the kinks in the US built version had been worked out. The USN decided on the Hispano as its standard future armament in June 1944.

 

[Glider]

You do realize the Navy did not accept the HS as is was unsuitable and spent over 15 years making changes to it and the ammo until it was.

I can only repeat what has been said before
a) The 20mm fitted in the USN aircraft post war were copies of the UK Hispano II and V both of which had seen considerable use and were reliable, something you have not tried to deny
b) You have not put any evidence forward to support your often made claim that the USN considered these weapons to be unsuitable.

Re the link if its the one in 335 I cannot open it.

Re your quote in 336 Including the USAAF, concluded in the late 1930s or early 1940s that 20 mm was the minimum preferable calibre for air to air cannon. RAF, Armée de l'Air, Luftwaffe, VVS, Regia Aeronautica, IJA, IJN and the USN all switched from LMG to 20 mm cannon during this period.
I don't see how this supports your case. It clearly states that the USAAF concluded (with everyone else) that the 20mm was the minimum for air to air cannon and as I stated all other airforces switched to 20mm during the war.

 

[Glider]

Just to add that I have been able to access the posting in your 335 and it had nothing to do with range. I have checked all the other links you posted and they had nothing to do with range. So I am awaiting your supporting evidence that range had anything to do with it.

You will recall that the reason that the USN gave for the 20mm was to do more damage in a shorter space of time hence the equiping of some F6-F5 nightfighters with 2 x 20mm. My brother reminded me that the USAAF presumably had the same requirement which is why the P61 had 4 x 20mm.

Just a thought

 

[zjtins]

Still waiting for your evidence for these claims...

Look at the film link its all there.

 

[zjtins]

b) You have not put any evidence forward to support your often made claim that the USN considered these weapons to be unsuitable.

It in the other forum link go read.

Standard fighter belting for the MG151/20 from 1942 onwards was 2 M'gschoss, 2 high explosive incendiary and either 1 or 2 AP HE or one API. Anti-bomber configurations had more M'gschoss, Eastern Front configurations had more AP, give the presence of the Il-2.

As you say prove it.

Everything I have read says the Germans changed rounds for whatever target they felt best used the resources something even personal preference AND by early 44 they were running out of both ammo and specific types of ammo.

I know (read in the past) that mid 43 German guns for the first time first time reduced in their allowance for chrome, nickel, cobalt copper tin. Somewhere there is paper about Speer and him quoting to Hitler war material production time left given certain metals. The ones that stick out in my mind was chrome, cobalt 21 months (this was in mid 43) and copper, aluminum <30 months. Tungsten for antitank round was 13 months, hence there shortage in 44-45.

Dont believe me if you do not want to, the rounds your quote I have no idea what they were based on. As time went on I really doubt the Germans had enough supplies to create the time delay and other exotic shells requiring limited resources, at least to any significant level.

Weird fact: they had plenty of coal, iron and chemicals for explosives, probably why it took so long to defeat them after D-day

 

[Glider]

Look at the film link its all there.

No it isn't. My evidence is simple all the USN aircraft which were fitted with 20mm cannon from the Helldiver in 1944 onwards. The USN would not have installed and used them if they were unsuitable.

Still waiting for the evidence re Range being a factor

 

[Jabberwocky]

As you say prove it.

Everything I have read says the Germans changed rounds for whatever target they felt best used the resources something even personal preference AND by early 44 they were running out of both ammo and specific types of ammo.

I know (read in the past) that mid 43 German guns for the first time first time reduced in their allowance for chrome, nickel, cobalt copper tin. Somewhere there is paper about Speer and him quoting to Hitler war material production time left given certain metals. The ones that stick out in my mind was chrome, cobalt 21 months (this was in mid 43) and copper, aluminum <30 months. Tungsten for antitank round was 13 months, hence there shortage in 44-45.

You really have no idea what you're talking about, do you?

From the 'Handbook on German Military Forces' published by the US War Department on 1 March 1945

MG151/20: "(3) Ammunition. Projectiles fired in this gun include high explosive, incendiary tracer, armour-piercing, armour-piercing high explosive and high explosive incendiary".

From Emmanuel Gustin, one of the two authors of 'Flying Guns':

20 mm (MG 151/20)

2 Minengeschoß m. Zerl.
2 Brandsprenggranatpatronen L'spur m. Zerl
oder Brandgranatpatronen
1 Panzersprenggranatpatrone o. Zerl
oder Panzerbrandgranatpatrone (Phospor) o. Zerl.

Here the Minengeschoß appears for the first time. A version of the 20mm M-Geschoß with tracer did not exist, so tracer was used on HE/I (Brandsprenggranatpatrone) or pure incendiary (Brandgranatpatrone) rounds. The latter was apparently a new development in 1944, intended to replace the less effective HE/I. The fifth round was a semi-AP projectile, explosive or incendiary. Apparently the main reason this was used instead of a solid AP round was that a solid projectile would have been too heavy.

It was recommended that more AP or semi-AP ammunition would be loaded when the probable targets were well-armoured attack aircraft such as the Il-2. On the other hand, against the four-engined bombers of the RAF and USAAF the high explosive types were more effective.

From the Catalog of Enemy Ordnance, published by US Office of Chief of Ordnance, in 1945

20 mm M.G. 151/20 (Mauser): Aircraft Machine Gun:

The following types of ammunition are used in the 20 mm version: H.E. with S.D. fuze; H.E.I./T. with S.D. fuze; A.P.I., A.P.H.E., and two different H.E.I. (S.D. fuze) rounds.

Finally, the ground version of the MG151/20 used the following ammunition, based on a 30 January 1945 German document:

2 cm Brandsprenggranatpatrone 151 mit L- oder Glimmspur mit Zerleger
2 cm Panzergranatpatrone 151 mit L-spuhr ohne Zerleger
2 cm Panzersprenggranatpatrone 151 mit und ohne Zerleger
2 cm Brandgranatpatrone 151 mit L- oder Glimmspur mit Zerleger
2 cm Panzergranatpatrone 151 (Ph) ohne Zerleger

Brandsprenggranatpatrone is HE-IT
Panzersprenggranatpatrone is AP-HET
Brandgranatpatrone is incendiary tracer
Panzergranatpatrone 151 (Ph) is AP-T with phosphorus content


Your turn, sport.

 

[zjtins]

So the USAAF which outnumber the nayv 2:1 is not relevant?

No it isn't. My evidence is simple all the USN aircraft which were fitted with 20mm cannon from the Helldiver in 1944 onwards. The USN would not have installed and used them if they were unsuitable.

Cite your source because this simply is not true.
Not sure of the production rates but the Corsair only had 300 20mm total delivered AFTER the war F4U-4: The last variant to see action during World War II, deliveries to the U.S. Navy of the F4U-4 began late in 1944.from wiki
Hellcat- Other prototypes in the F6F series included the XF6F-4 (02981, a conversion of the XF6F-1 powered by an R-2800-27 and armed with four 20mm M2 cannon) which first flew on 3 October 1942 as the prototype for the projected F6F-4. {wiki} appears only night fighters got the 20mm, a small portion of production


HS404 comments

The gun was heavy and normally fired from a 60-round drum. Smaller drums were devised for flexible mountings, and a 160-round drum was designed for fixed guns, though this was unreliable if loaded with more than about 150 rounds. The somewhat low rate of fire was compensated by an unusually powerful cartridge.

The gun averaged one jam every 1500 rounds under good operating conditions, but twice that rate under dusty conditions. The gun was more vulnerable than the Browning to cold temperatures at high altitude. American-manufactured Hispanos were particularly unreliable and the gun was disliked by most American pilots. Those installed on the SB2C were particularly notorious for jams, although the problems were largely worked out in the SB2C-4 and may have been due as much to poor maintenance as anything else in the earlier SB2Cs.

There is my non reliable citation

 

[Aozora]

Sure but what more likely a .50 hitting mostly near center mass or a 20mm taking out lines with random shrapnel. Basically from any direction only the very outside edge of the enginee would a .50 bounce off which equates to asmall percent of the target.

Also a 20mm could not penetrate pilot armor (backseat)...it hurts but cannot penetrate the .50 could and did. Again my point is the info to date is energy based NOT terminal ballistics, target type and and round actual affect data.

Still awaiting any proof of any of this. Still awaiting any substantive evidence that the Americans adopted the .50 because it was better than the 20mm cannon of other nations. All you have shown so far is that the .50 was adopted en masse by the Americans because it was their only reliable weapon available in quantity in time, not because it was better overall.

The British adopted the 20mm Hispano and persevered with it, in spite of the initial problems, because it was deemed to be more effective and useful than the .50 cal Browning: all of the British aircraft specifications for fighters, bomber and ground attack aircraft issued just before and during the war specified 20mm cannon as the main armament

But that was not my comment. It is that the 6 or 8 .50 were good enough for the day, and did not see a need to switch to 4x20mm. In WWII the US did not have production capability of either 20mm guns or ammo. They could produce massive amounts of .50 guns and ammo.

Nor did I claim the US should stick with the .50 for Kamikaze as AAA. I brought it up to show there were situations where the 20mm was NOT effective.

There were also plenty of situations where the .50 cal was even less effective than the 20mm, such that the Americans mostly replaced the .50 cal with 20mm on their ships. Simply stating the 20mm was not effective in some situations is about as useful as stating a potato was even less effective.

Fact is the only country continuing to use the .50 cal as the main armament during the war was the USA - all other major airforces adopted 20mm weapons as their main weapons load, with large calibre mgs as a back-up. Yes, the .50 was effective, but you can bet had the Americans been able to develop a decent 20mm cannon the .50 would have become secondary.

 

[Jabberwocky]

HS404 comments

The gun was heavy and normally fired from a 60-round drum. Smaller drums were devised for flexible mountings, and a 160-round drum was designed for fixed guns, though this was unreliable if loaded with more than about 150 rounds. The somewhat low rate of fire was compensated by an unusually powerful cartridge.

The gun averaged one jam every 1500 rounds under good operating conditions, but twice that rate under dusty conditions. The gun was more vulnerable than the Browning to cold temperatures at high altitude. American-manufactured Hispanos were particularly unreliable and the gun was disliked by most American pilots. Those installed on the SB2C were particularly notorious for jams, although the problems were largely worked out in the SB2C-4 and may have been due as much to poor maintenance as anything else in the earlier SB2Cs.

One jam per 1500 rounds would make the 20 mm Hispano MORE reliable than the .50 Browning - depending on who built it. One jam per 750 rounds would make it slightly better than half as reliable.

Over the first 8 months of 1944, the USAAF 8th AF found that the M2 Browning averaged 1 stoppage per 1440 rounds. The 20 mm AN/M2 averaged 1 stoppage per 505 rounds, making the .50 cal almost three times as reliable in US service.

The US Bureau of Ordnance found a stoppage rate in Africa of about 1 stoppage per 1300 rounds.

In comparison, the RAF found between D-Day and the end of the war that their Hispanos averaged 1 stoppage per 1560 rounds. Their M2s jammed about 1 per 2,400 rounds.

The main problem with the Hispano was sensitivity to cold temperatures (which caused jamming in the P-38 in the ETO and also Spitfires over Darwin), a sensitivity to dust (which affected Spitfires and Hurricanes in the MTO and also Spitfires over Darwin) and some sub-standard manufacturing in the feed mechanism and belts (responsible for more than 50% of jams). Once the gun heating problem was sorted in 1942, the RAF reported reliability was more than adequate, with one stoppage recorded per 1600 rounds. Given that the gun life was only about 2,000 rounds, this was seen as sufficient.

If the US hadn't buggered up their re-design, the 20 mm would have been comparably reliable to the .50 cal, at least if maintained properly.

 

[Shortround6]

Cite your source because this simply is not true.
Not sure of the production rates but the Corsair only had 300 20mm total delivered AFTER the war F4U-4:

Simply is not true. 200 F4U-1Cs were built starting in July 1944 with four 20mm guns. A small number to be sure but shows which way the Navy was going. It took 3-5 months to get a plane from the factory door into action. It could also take around a year from when a plane was ordered until it was delivered. After the Fall of 1944 the NAVY did NOT ORDER an new fighter with .50 cal guns. All fighters armed with .50 cal guns delivered in 1945/46 had been ordered prior to the end of 1944.

HS404 comments

There is my non reliable citation

It sure is "non reliable". I am not sure who used the 160 round drum, if anybody. British were using belt feeds by 1941. Most American aircraft used Belt feeds. The somewhat slow rate of fire needs to compared to other guns and put in a time context. For part of 1940 the .50cal M2 Browning did NOT fire any faster than a drum feed HS404. Then the M2 was sped up to fire 13-14 rounds a second compared to the Hispanos 10 rps.

 

[Glider]

Cite your source because this simply is not true.

Use your eyes, find any USN type that entered service after the SB2C that didn't have 20mm

appears only night fighters got the 20mm, a small portion of production

Now why would that be if range was the major factor for wanting the 20mm?
Maybe its because thay wanted to do the maximum damage in the minimum amount of time as per the USN rep at the fighter conference, but I know you dont normally go along with that


HS404 comments

There is my non reliable citation [/QUOTE]
If I may use your own quote
Those installed on the SB2C were particularly notorious for jams, although the problems were largely worked out in the SB2C-4 and may have been due as much to poor maintenance as anything else in the earlier SB2Cs.
Once again your own evidence does you in.

 

[zjtins]

Use your eyes, find any USN type that entered service after the SB2C that didn't have 20mm

So do not ask me for a source since you cannot share yours, if you actually have any...

There is my non reliable citation If I may use your own quote
Those installed on the SB2C were particularly notorious for jams, although the problems were largely worked out in the SB2C-4 and may have been due as much to poor maintenance as anything else in the earlier SB2Cs.
Once again your own evidence does you in.

Exactly they were not reliable.

 

[zjtins]

All you have shown so far is that the .50 was adopted en masse by the Americans because it was their only reliable weapon available in quantity in time, not because it was better overall.

You miss the point, I never said it was better overall I said it was sufficient for WWII.

 

[zjtins]

The USAAF wanted to switch to a larger calibre than .50 cal, but was frustrated by its own inability to do so

Now the USAAF? cite something as this (I missed) I have never seen.

 

[zjtins]

Quite true but then which guns in which air force are you comparing? The ONLY US fighters that used Drums were were the P-400s, some P-70s and few odd balls. The P-38 carried 150 rounds, the P-51 with 20mm cannon carried 125 rpg. P-61 carried 200rpg,

Back to one plane again, what about the Spit, MGFF on German ....all drum all problematic.

 

[zjtins]

A 20mm would destroy an engine,

Go read bob Johnston P-47 book numerous examples of engine pieces blown off and plane got home. I never said the 20mm could not cause damage but the myth vs fact is more than one round in air cooled engine was needed to bring a plane down with a high confidence.
And no matter how much you quote technical specs that is not combat damage records the only true measure.

 

[zjtins]

If you think that a single 46 gram .50 bullet will wreck and engine when a 128 gram AP 20mm round going about the same speed won't then I guess the laws of physics have been repealed.

You apparently do not understand damage physics. There is simply is no way to predict or compare prediction for mechanical vs chemical damage, they use different physics.

A .50 cal bullet going through Al skin leaves .50 cal hole, the explosive creates over pressure. The overpressure if constrained (as in a time delay and is inside the plane) expand until a opening is found a one is created at the weakest points.
OTOH a 20mm impact and detonation on the surface of hard object (engine) only has overpressure (generally at point of impact) to damage the hard object. Cast iron and steel can take alot of overpressure. But SAPI .50 round breaks the brittle engine metal. Cracks propagate especially under load. They also can a did pierce the armor plate and other hard objects. The 20mm did not generally go through Armor plate. (Read Bobs book he took several 20mm hits in the armor in his P-47).

I know there was a good cite on mixed belts earlier. I have no response to than except reading pilots stories, for whatever reason, I do not see a correlation. For Germany at least in 44 and 45 what they were ordered and what they got appear to be not the same. At least the US pilot stories do bear out the effectiveness of aformentioned mixed belts. So either they were not as mixed as orderd, they were not as effective as thought, or another unknown cause. I guess at best, based on US pilot accounts, the damage most mentioned appear to have come from 20mm minegesshoss or other non penetrating rounds.

 

[Glider]

You miss the point, I never said it was better overall I said it was sufficient for WWII.

For the USAAF I agree!! But the USN wanted something more