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TeaWagon
08-06-2005, 07:09 AM
My book finally arrived in the mail, and is turning out to be a good read. This tome is...

"Flying Guns of World War II; Development of Aircraft guns, ammunition, and installations 1933-1945" by Anthony G. Williams and Emmanuel Gustin.

Below I will provide a quote on some aircraft weapons that seem to be popularly debated in these circles from the book. Quoted, from pages 40 - 42...

"The German approach represented a completely different philosophy from that of the USAAF. Instead of using the kinetic energy of large numbers of high-velocity AP bullets to destroy the target, the Luftwaffe relied on the blast effect of large quantities of HE detonating within the structure. Both approaches seemed to work well, but of course the USAAF generally only had to attack enemy fighters (for which HMGs were usually powerful enough), not bombers. By the end of the war, the M-Geschoss had become the standard German type of aircraft cannon projectile, and it was widely adopted by other air forces post-war. Hollow-charge projectiles were developed for the 30mm guns, but it appears that they did not see service; in fact, only in recent years have the problems of using such technology in small-calibre cannon ammunition been solved.

As we have seen, the British were systematic in testing whatever German guns and ammunition they could get hold of against realistic aircraft targets, and they concentrated hard on the 20mm guns, particularly with HE ammunition. They discovered the following:

* In firing trials against bullet-proof Triplex glass at a range of 46m and a striking angle of 45 degrees, an MG-FF firing HE/T projectiles could penetrate 3.8 cm glass but not 6.35 cm.

* HEI with instant-action fuse fired from an MG-151/20 at 183m would detonate on a Perspex canopy, with the fragments making little impression on the armour behind.

* The same ammunition set light to a self-sealing wing fuel tank of a Blenheim light bomber with three shots out of eight.

* The same ammunition could be protected against by 12mm face-hardened armour, or just 6.6mm homogeneous armour (which was less brittle.)

* For comparison purposes a few rounds of 20mm Hispano HEI were fired at the same target as above. The test report commented that although the German HEI (M-Geschoss) contained more explosive, the powerful Hispano stood more chances of doing serious damage - such as the breaking of spar flanges - or of reaching the fuel tanks.

* A test of German 20mm incendiary/tracer ammunition showed that it was remarkably effective, with 17 out of 22 rounds hitting the usual Blenheim wing tank causing fires; but 14 rounds ignited prematurely and flashed at the muzzle, and these proved ineffective. The ammunition was judged to be faulty.

The 30mm HEI M-Geschoss, fired from an Mk-108, was also tested. Unsurprisingly, ten rounds fired at a Spitfire fuselage resulted in a score of three immediately lethal, seven probably lethal. Eleven rounds fired at a Blenheim achieved the same results, plus one doubtful. The Germans discovered that a wing hit on a B-17 resulted in a hole of 100 x 175 cm. It was noted that the ammunition did not have much effect on heavy bomber fuselages (presumably because of the large volume for th explosion to dissipate into), but inflicted serious aerodynamic damage to the wings by blowing off the surfaces, and that the incendiary content was very effective in starting fires. German tests reflected these results, and also revealed significant differences on the construction of the aircraft. Stressed-skin alloy monococque structures were most vulnerable to being blown apart. Steel structures clad with thin aluminum were less affected as the cladding quickly split, releasing the pressure before it had much time to damage the structure, and fabric-covered structures, such as the Wellington bomber, were damaged least of all. It was not only the blast which inflicted damage; after the war, the Americans test-fired an MK-108 HEI shell into the tail of a B-24 at a typical angle, characteristic of a tail interception by an Me-262. The 'spray' pattern of very high-velocity, very small fragments cut most if not all of the control cables and many of the longerons. It was assessed that the tail would have separated if the plane had been in flight: a performance which made a great impression on the observers. Protective measures could be taken against blast effects, and it was discovered that a 20mm thick strong rubber foam mat lining compartments significantly reduced the effect.

The British and American 20mm Hispano HE/HEI shells were conventional thick-walled designs with more limited HE capacity but considerable kinetic energy. They also produced larger and heavier fragments than the M-Geschoss when they burst, which would have carried further and penetrated more deeply. The British Mk 1.z HE shell was expected to a blow a hole between 75mm and 200mm in diameter in 12mm armour plate, while scattering shell fragments up to 5 meters. British tests of the HEI revealed that coolant, lubricant and fuel systems would be holed by fragments resulting from hits on engine cowlings, and detonation some 75mm from a self-sealing tank would result in a hole over 50mm in diameter, causing leakage of 1,900 litres per hour. Whether a Hispano HEI or a 20mm M-Geschoss would do most damage depended on the aircraft being attacked, and exactly where the shell detonated.

The Soviets selected a relatively light projectile weight of 91 - 99 grams for the ShVAK's 20 x 99R cartridge, although they did not have the benefit of M-Geschoss technology. Heaviest was the API Type BZ, which had a sub-calibre hard steel penetrator, the jacket tip being filled with incendiary material. The HEI Type OZ had a very small HE capacity, representing only around six percent of the weight. The 23mm projectiles used in the Vya and the NS-23 went to the other extreme, weighing an impressive 200 grams. The type BZ API was still steel-cored, with 6.6 grams of incendiary compound in the tip, while the Type OZT HEI/T, and the 37mm HE shell, again had only a small percentage of their weight devoted to HE. They were clearly expected to inflict most damage by fragmentation rather than blast effect; British tests of the Vya HEI revealed that blast effects were similar to those of hte 20mm Hispano HEI.

Japanese cannon projectiles varied between the heavy (IJN 20mm Type 99 projectiles weighed around 128 grams, the IJA's Ho-1 and Ho-3 up to around 127-136 grams) to the very light (IJA 20mm Ho-5 as little as 79 grams). AP projectiles were of the cannon type (I.E. Solid steel) rather than using sub-calibre cores. HE shells generally had a modest filling ratio, although the little 79 grams Ma 202 HEI used in the Ho-5 managed an impressive - for a non-M-Geschoss - fifteen percent change/weight figure by virtue of its fuseless design: where a fuse would normally be was a PETN HE exploder (the equivalent of the more powerful Ho-1 and Ho-3 being the 109 gram HEI). Larger cannon shells such as the IJN 30mm Type 2 HE and the 37mm shell used in the Ho-203 and Ho-204 also varied in their change/weight ratios.

The frequent use of unprotected PETN exploders in Japanese ammunition must have represented a significant handling risk, and does not appear to have been copied by other countries."

End Quote. Well, I think I've worn down my fingers enough. Enjoy; if you're interested at all in WWII aviation weaponry, this book is an excellent read and source of information.

TeaWagon

BBB_Hyperion
08-06-2005, 09:40 AM
Anthony G. Williams wrote a correction on German Ammo to it conclusion was difference between hispanio and mg151 wasnt that much as though in older versions of the book. Must be somwhere on his site. Sometimes he even answers his mails http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif.

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

The MG FF is btw no MG151/20 which have significant differences in precision and rpm etc . The premature exlosion of mine sheels are most likely a result of the early fuses used that got continously improved . Later on the explosive which is nitropenta or Ha 41 . With HA41 and VC or VD Capsules the pressure burst effect was increased by 40 % towards normal nitropenta load.

Later even a 25 g explosive load duo compression of explosive material was called MX Shells with same size was available.

tigertalon
08-06-2005, 10:49 AM
Originally posted by TeaWagon:
and detonation some 75mm from a self-sealing tank would result in a hole over 50mm in diameter, causing leakage of 1,900 litres per hour.


Oleg was right in 3.04 about Fw fuel leak "bug" after all! http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

Thank you TeaWagon for typing, gotta check for this book!

TeaWagon
08-06-2005, 12:28 PM
A shame their method of fixing it in the current version, 4.01m, has been to make the FW-190 totally unable to leak fuel or have its fuel tank set on fire.

But I digress. The FW-190 or any other type is in no way unique in terms of flight and damage model abnormalities, but part of a much larger and more amusing cadre of bugs and other oddities that have been present in this flight simulator from the beginning. All to be noted, reported, grinned at, and ultimately fixed, in my opinion. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

TeaWagon

TAGERT.
08-06-2005, 12:56 PM
Originally posted by TeaWagon:
My book finally arrived in the mail, and is turning out to be a good read. This tome is...

"Flying Guns of World War II; Development of Aircraft guns, ammunition, and installations 1933-1945" by Anthony G. Williams and Emmanuel Gustin.

Below I will provide a quote on some aircraft weapons that seem to be popularly debated in these circles from the book. Quoted, from pages 40 - 42...

"The German approach represented a completely different philosophy from that of the USAAF. Instead of using the kinetic energy of large numbers of high-velocity AP bullets to destroy the target, the Luftwaffe relied on the blast effect of large quantities of HE detonating within the structure. Both approaches seemed to work well, but of course the USAAF generally only had to attack enemy fighters (for which HMGs were usually powerful enough), not bombers. By the end of the war, the M-Geschoss had become the standard German type of aircraft cannon projectile, and it was widely adopted by other air forces post-war. Hollow-charge projectiles were developed for the 30mm guns, but it appears that they did not see service; in fact, only in recent years have the problems of using such technology in small-calibre cannon ammunition been solved.

As we have seen, the British were systematic in testing whatever German guns and ammunition they could get hold of against realistic aircraft targets, and they concentrated hard on the 20mm guns, particularly with HE ammunition. They discovered the following:

* In firing trials against bullet-proof Triplex glass at a range of 46m and a striking angle of 45 degrees, an MG-FF firing HE/T projectiles could penetrate 3.8 cm glass but not 6.35 cm.

* HEI with instant-action fuse fired from an MG-151/20 at 183m would detonate on a Perspex canopy, with the fragments making little impression on the armour behind.

* The same ammunition set light to a self-sealing wing fuel tank of a Blenheim light bomber with three shots out of eight.

* The same ammunition could be protected against by 12mm face-hardened armour, or just 6.6mm homogeneous armour (which was less brittle.)

* For comparison purposes a few rounds of 20mm Hispano HEI were fired at the same target as above. The test report commented that although the German HEI (M-Geschoss) contained more explosive, the powerful Hispano stood more chances of doing serious damage - such as the breaking of spar flanges - or of reaching the fuel tanks.

* A test of German 20mm incendiary/tracer ammunition showed that it was remarkably effective, with 17 out of 22 rounds hitting the usual Blenheim wing tank causing fires; but 14 rounds ignited prematurely and flashed at the muzzle, and these proved ineffective. The ammunition was judged to be faulty.

The 30mm HEI M-Geschoss, fired from an Mk-108, was also tested. Unsurprisingly, ten rounds fired at a Spitfire fuselage resulted in a score of three immediately lethal, seven probably lethal. Eleven rounds fired at a Blenheim achieved the same results, plus one doubtful. The Germans discovered that a wing hit on a B-17 resulted in a hole of 100 x 175 cm. It was noted that the ammunition did not have much effect on heavy bomber fuselages (presumably because of the large volume for th explosion to dissipate into), but inflicted serious aerodynamic damage to the wings by blowing off the surfaces, and that the incendiary content was very effective in starting fires. German tests reflected these results, and also revealed significant differences on the construction of the aircraft. Stressed-skin alloy monococque structures were most vulnerable to being blown apart. Steel structures clad with thin aluminum were less affected as the cladding quickly split, releasing the pressure before it had much time to damage the structure, and fabric-covered structures, such as the Wellington bomber, were damaged least of all. It was not only the blast which inflicted damage; after the war, the Americans test-fired an MK-108 HEI shell into the tail of a B-24 at a typical angle, characteristic of a tail interception by an Me-262. The 'spray' pattern of very high-velocity, very small fragments cut most if not all of the control cables and many of the longerons. It was assessed that the tail would have separated if the plane had been in flight: a performance which made a great impression on the observers. Protective measures could be taken against blast effects, and it was discovered that a 20mm thick strong rubber foam mat lining compartments significantly reduced the effect.

The British and American 20mm Hispano HE/HEI shells were conventional thick-walled designs with more limited HE capacity but considerable kinetic energy. They also produced larger and heavier fragments than the M-Geschoss when they burst, which would have carried further and penetrated more deeply. The British Mk 1.z HE shell was expected to a blow a hole between 75mm and 200mm in diameter in 12mm armour plate, while scattering shell fragments up to 5 meters. British tests of the HEI revealed that coolant, lubricant and fuel systems would be holed by fragments resulting from hits on engine cowlings, and detonation some 75mm from a self-sealing tank would result in a hole over 50mm in diameter, causing leakage of 1,900 litres per hour. Whether a Hispano HEI or a 20mm M-Geschoss would do most damage depended on the aircraft being attacked, and exactly where the shell detonated.

The Soviets selected a relatively light projectile weight of 91 - 99 grams for the ShVAK's 20 x 99R cartridge, although they did not have the benefit of M-Geschoss technology. Heaviest was the API Type BZ, which had a sub-calibre hard steel penetrator, the jacket tip being filled with incendiary material. The HEI Type OZ had a very small HE capacity, representing only around six percent of the weight. The 23mm projectiles used in the Vya and the NS-23 went to the other extreme, weighing an impressive 200 grams. The type BZ API was still steel-cored, with 6.6 grams of incendiary compound in the tip, while the Type OZT HEI/T, and the 37mm HE shell, again had only a small percentage of their weight devoted to HE. They were clearly expected to inflict most damage by fragmentation rather than blast effect; British tests of the Vya HEI revealed that blast effects were similar to those of hte 20mm Hispano HEI.

Japanese cannon projectiles varied between the heavy (IJN 20mm Type 99 projectiles weighed around 128 grams, the IJA's Ho-1 and Ho-3 up to around 127-136 grams) to the very light (IJA 20mm Ho-5 as little as 79 grams). AP projectiles were of the cannon type (I.E. Solid steel) rather than using sub-calibre cores. HE shells generally had a modest filling ratio, although the little 79 grams Ma 202 HEI used in the Ho-5 managed an impressive - for a non-M-Geschoss - fifteen percent change/weight figure by virtue of its fuseless design: where a fuse would normally be was a PETN HE exploder (the equivalent of the more powerful Ho-1 and Ho-3 being the 109 gram HEI). Larger cannon shells such as the IJN 30mm Type 2 HE and the 37mm shell used in the Ho-203 and Ho-204 also varied in their change/weight ratios.

The frequent use of unprotected PETN exploders in Japanese ammunition must have represented a significant handling risk, and does not appear to have been copied by other countries."

End Quote. Well, I think I've worn down my fingers enough. Enjoy; if you're interested at all in WWII aviation weaponry, this book is an excellent read and source of information.

TeaWagon Very Interesting, Ill have to get that book! Thanks for the heads up!

TeaWagon
08-07-2005, 10:32 AM
I found another good exert from the book, this time dealing with Armour penetration. The following quote is from page 46 - 47. Quote...

"Comparisons between the penetration achieved by different armour-piercing cartridges are problematic for several reasons. First, penetration figures are often quoted at different distances and striking angles (incidentally, striking angles in this work are all quoted using the convention that the most favourable angle for penetration, perpendicular (or 'normal') to the armour, is measured as 90 degrees; some other conventions have described this as 0 degrees). Much less obviously, different qualities of armour are sometimes assumed. There have also been various national definitions of 'penetration'; some (e.g. the US) specified that 50 percent of the shots fired have to pass through the target, others required signficantly higher percentages, or did not require the shot to pass completely through the target. Finally, AP performance was usually measured on the ground. When fired from an aircraft, the actual figure would be slightly reduced in a tail chase due to increased air resistance (less of an effect at high altitude), but would be increased when firing at ground targets because the speed of the aircraft was added to the muzzle velocity, and considerably increased in a head-on attack.

In addition to these problems, the actual performance of AP projectiles in battle can vary considerably from that achieved on test. In particular, passing through the thin aluminium aircraft skin can induce yaw, i.e. disturb the straight flight of the projectile away from travelling point-first, so that it fails to hit the armour head-on, thereby significantly reducing its penetrative abilities. In fact the degree of obstruction caused by aircraft structures is such that armour much thinner than theory indicated would be necessary was often found to give satisfactory results.

The most exhaustive tests during the Second World War seem to have been carried out in Germany. Official penetration curves for 7.92mm AP rounds tested in 1942 are worth examining in detail because they reveal the variations wihch can occur. The SmK-v (Spitzgeschoss mit Stahlkern verbessert, improved pointed bullet with steel core) achived the following:

At 100 meters:- 12mm/90 degrees - 8mm/60 degrees - 3.5mm/30 degrees

At 300 meters:- 9mm/90 degrees - 6mm/60 degrees - 3mm/30 degrees

At 600 meters:- 6mm/90 degrees - 3.5mm/60 degrees - 1.5mm/30 degrees

However, if the bullet first penetrated at 3mm dural (light alloy) aircraft skin angled at 70 degrees, armour penetration at 100 meters dropped to 4mm/90 degrees, 3mm/60 degrees and 2.5mm/30 degrees.

These results are supported by tests carried out by the British in January 1941 to compare British and German rifle-calibre steel-cored AP ammunition. The performance of the .303 (11.28 grams at 735 meters/second) and the 7.92mm (of unspecified type, but measured at 11.53 grams at 788 meters/second) was first tested against 'homogeneous hard armour'. The thickness necessary to achieve immunity from this ammunition at 183 meters (200 yards) was 12.0 mm for the .303 in, 12.5mm for the 7.92mm, when striking 'at normal' to the armour (i.e. at 90 degrees). The British ammunition was significantly worse when the striking angle changed to 70 degrees; only 6.6mm was needed for immunity in comparion with 8.9mm to protect against the German round.

The test then changed to shooting at the rear of the long-suffering Bristol Blenheim at the same distance, involving penetrating the rear fuselage before reaching the 4 mm armour plate protecting the rear gunner, which was angled at 60 degrees to the line of fire. The results in this case were reversed: 33 percent of the .303 in rounds reached the armour and 6 percent penetrated it. In contrast, only 23 percent of the 7.92mm bullets reached the armour, and just 1 percent penetrated. The British speculated that the degree of stability of the bullets (determined by bullet design and the gun's rifling) might have accounted for these differences.

Continuing with the German ammunition (for which more detailed records seem to survive than any other nation's during the period), it is instructive to compare some of the standard AP types in different calibres. The little 13 x 64B Pzgr for the MG-131 was capable of penetrating 17mm/100 meters/90 degrees, but this dropped to just 10mm/60 degrees and 4mm/30 degrees (equivalent figures at 300 meters being 11mm/90 degrees and 7mm/60 degrees). On the other hand, the consequences of hitting the dural plate were negligible, only reducing penetration by 1 or 2 mm.

Before turning to the 20 mm cannon it is worth mentioning the performance of the .50 in Browning. The official requirement for the M2 AP way to penetrate 22mm steel at 183 meters (200 yards) (the M8 API was expected to match this figured at 92 meters). The striking angle is not specified but assumed to be 90 degrees. Official US tables for the M2 show penetration at 300 meters as follows: 21mm/90 degrees, 13mm/60 degrees, 5mm/30 degrees.

These measurements were to the USN criterion which called for 50 percent of shots to penetrate. British tests at 183m determined that the M2 would penetrate 21mm at 0 degrees angle of yaw (i.e. the bullet was flying perfectly straight), but this dropped to 15mm with only 10 degrees of yaw (such as might be caused by passing through an aircraft's skin before hitting the armour). Further tests at 90 meters firing through a heavy bomber fuselage demonstrated an ability to penetrate between 14 and 20 mm when firing at angles of between 57 and 77 degrees. German tests credited the M2 with a penetration of 25mm/100 meters/90 degrees, falling to only 10mm after passing through the dural skin (the 12.7mm Berezin API was even worse affected, falling from 25mm to 8.5mm). Taking the effects of typical ranges, striking angles and fuselage structures into account, it seems likely that the practical penetration of either the M2 or M8 was in the region of 10-15 mm in normal circumstances. This was generally adaquate for dealing with aircraft armour, although it should be noted that Finnish pilots using Brewster Buffalos armed with .50 in Brownings reported considerable difficulty in shooting down Soviet fighters from directly behind, and recommended attacking from a slight angle in order to fire past the rear armour plate.

German 20mm ammunition did not have sufficient velocity to justify the use of Hartkernmunition, so the AP types were plain steel with some incendiary content, the 117 gram Pzbr containing a capsule with 3.6 grams of phopshorous. The low velocity (under 600 m/sec) MG-FFM, usually derided for its lack of penetration, was actually quite satisfactory when loaded with one of the various Pzgr projectiles which seem to have become available from 1941. Maximum penetration (100 m/90 degrees) varied between 18 and 24 mm depending on type, with the more realistic 300m/60 degree giving figures of 9-10 mm. The effect of prior penetration of the usual angled 3mm dural skin varied hugely, from about 5 percent to around 40 percent reduction, depending on the projectile type and the striking angle. As one would expect, the results for the higher velocity MG-151/20 firing the same projectiles was slightly better, at 12-13mm/300m/60 degrees. The British considered what thickness of armour was required to protect against this ammunition, and determined that for a bomber around 15-18mm would be adaquate, although for protecting the rear of the existing Spitfire and Tempest fighters the best solution within the weight limits would be two plates of 7mm and 4mm, 150mm apart.

The Allied 20mm Hispano was significantly more powerful than the MG-151/20, but little attempt seems to have been made to exploit this in terms of armour penetration. As already described, the RAF settled on a mixture of HEI and a SAPI projectile which was specified to penetrate 20mm/200 meters/90 degrees and ignite petrol in cans behind the plate. This was regarded, with some justification, as entirely adequate to deal with enemy aircraft. The US M75 AP shot for this cartridge was claimed to penetrate 18mm homogeneous plate or 16.5mm face-hardened armour at 457 meters/70 degrees. Another US official source gives penetration at 300m as follows: 31-39 mm/90 degrees (depending on the armour hardness), 19mm / 60 degrees and 10mm/30 degrees (presumably for average armour hardness). The Germans surprisingly credited this loading with only 25 mm/100m/90 degrees, although noted that passing through the usual dural skin only reduced this to 21mm. The British did experiment with a tungsten-cored type, similar to Hartkernmunition (the AP Mark III.z) designed by Janecek of 'squeezebore' gun fame, which was intended to penetrate up to 60 mm/200 m/70 degrees, but it seems that it was ballistically unsatisfactory and was not adopted.

The Soviet 20mm ShVak API, which like their 12.7mm had a hard steel core with the incendiary mixture in the tip of the jacket, preformed erratically in the german tests, achieving 24mm/100m/90 degrees, but only 7mm after passing through the dural skin. In the same test, the figures for the 23mm Vya (taken at 300m instead of 100m) were 30mm and 16mm respectively.

One curious aspect of AP performance is that the maximum damage to the aircraft to the aircraft structure was caused when the projectile had only just enough power to penetrate; higher velocities than this merely punched neater holes."

Okay, enough for now. Hope all those that read my original post take further interest. Please note, this is not the full text of those pages, as I had to delete some out to fit within the 10,000 character limit.

TeaWagon

JG54_Arnie
08-08-2005, 06:18 AM
Very interesting man, thanks! http://forums.ubi.com/images/smilies/25.gif

Kocur_
08-08-2005, 09:29 AM
Thank you very much! Very interesting!

Im surprised by this:

"Americans test-fired an MK-108 HEI shell into the tail of a B-24 at a typical angle, characteristic of a tail interception by an Me-262. The 'spray' pattern of very high-velocity, very small fragments cut most if not all of the control cables and many of the longerons."

I never thought Minengeschoss thin walls produced fragments large enough to damage anything vital, and surely not longerons!


Using data from the last of methods of assesement of projectiles effectiveness BBB_Hyperion posted I calculated (a while ago http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif) M2' equivalent BH. Mk.II equal to 3,6 , assuming (wrong of course: that all cartidges in M2 belts had API, and all cartidges in BH. Mk.II belts had HE, seems that its more in M2 favour).
3,6 is worse than often quoted 3,3 figure. Seems that if take under consideration projectile yaw effect. i.e. disturbance of projectile trajectory (plus tip circular movement much increased) caused by distubated rotation caused by penetration of planes skin at low angle, the ratio was even worse...

faustnik
08-08-2005, 11:06 AM
This is a great book, I really enjoyed reading it. It is one of those reference books that you can look at many times and always find something new and interesting. http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

The charts in appendix 6 rate the effectiveness of various cartridges. The Mg151 minengeschoss round is rated as significantly more effective than the Hispano HE round and almost twice as effective as the ShVak HE round. The Mg151 is rated as more efficient than either the Hispano or Shvak.

Flying Guns of World War II pages 330-331.

HayateAce
08-08-2005, 12:02 PM
The Allied 20mm Hispano was significantly more powerful than the MG-151/20....





http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif

faustnik
08-08-2005, 12:09 PM
Originally posted by HayateAce:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">

The Allied 20mm Hispano was significantly more powerful than the MG-151/20....






http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif </div></BLOCKQUOTE>

You have a problem with that? Are you more of an expert than Mr. Williams?

TeaWagon
08-08-2005, 04:05 PM
If you would, Faustnik, please do not pay his post any heed. Science, facts, and proof is too little for many to overcome their impressions and prejudices, and this often applies to far more than the power of aircraft weaponry. I don't like to have my threads hijacked, after all. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Not to mention the difficulty in which some have at differentiating such difficult concepts as efficiency and effectiveness.

I will post again shortly on what the book explains were typical ammunition use and mixtures.

tigertalon
08-09-2005, 05:35 AM
Interesting read, TeaWagon, Ty again for typing.

HayateAce, I think here he ment the proppelant filling (which is important at armour-piercing as it increases muzzle velocity), not the explosive content of a shell.

TeaWagon
08-09-2005, 07:40 AM
Actually, if you read carefully, you'll see Tony Williams meant just what he said.

From the second quote... - "The Allied 20mm Hispano was significantly more powerful than the MG-151/20, but little attempt seems to have been made to exploit this in terms of armour penetration."

This is by virtue of the weapon itself. The 20mm Hispano fires a heavier round at considerably faster muzzle velocity, meaning its kinetic power is superior. This has nothing to do with the type of ammunition used and their comparable destructiveness. Of this, he mentions in the first post.

From the first quote... "Whether a Hispano HEI or a 20mm M-Geschoss would do most damage depended on the aircraft being attacked, and exactly where the shell detonated."

Meaning there were more variables to account for than one would think. The structure of the aircraft and how it resists more HE material to smaller, thinner fragments in the case of the Minengeschoss and less HE material to larger, thicker fragments in the case of the Hispano HEI, and just where these shells hit, are both important factors.

I think it is fair to say that the Hispano HEI and German Minengeschoss were comparable in destructive power, though by virtue of the weapon itself, the kinetic power of the Hispano round as fired from the Hispano gun is superior. Note though, that because of the heavy weight of the Hispano as compared to the MG-151/20 and the MG-151/20's higher rate of fire (12 rounds a second compared to 10) makes the german gun undoubtedly a more efficient weapon.

Anyway... The next post I'm going to elaborate on what the book mentions for Ammunition Belt Make-Up, so hang with me.

TeaWagon
08-09-2005, 08:21 AM
From Page 49 to 51... Quote.

"Ammunition Belt Make-Up

The pros and cons of the different types of projectiles were such that virtually all air forces loaded a mix of different types in each ammunition belt, although the exact make-up depended on the nationality, the gun and the circumstances, and varied over time. Unfortunately, comprehensive records do not seem to have survived, but in any case they would be of doubtful value because this was one choice which individual pilots or gunners often made for themselves (with or without official approval) as the ammunition belts were generally filled by ground crew at each station. What follows is therefore only indicative.

It should incidentally be noted that while disintegrating link steel belts were standard issue in the Second World War, some of the German ones could be changed between disintegrating and non-disintegrating modes as required. For a while in 1943 fabric belts were issued for some American .50 in Browning guns due to a production shortfall in metal belts (although there is some doubt about whether these were used in aircraft, which had priority for steel belts). Some guns (e.g. the US 37mm M4 and IJA 37mm Ho-203 and 57mm Ho-401) used 'closed-loop' belts which were built into the magazine and non-disintegrating.

The RAF fighters armed with eight .303 in guns differed from the usual practice by loading each gun with only one type of ammunition. During the Battle of Britain in 1940, the reported use was three guns loaded with ball, two with AP, two with Mk IV incendiary tracer (the incendiary material ignoted on firing and burned throughout the flight, giving a tracer effect) and one with Mk VI incendiary (the 'De Wilde'). It is not clear why the Mk VI was used so little or why ball was used at all, possibly there was a shortage of the more effective loadings.

RAF Bomber Command principally used .303 in guns for defensive fire. In 1942 the approved ratios for loading the belts in four-gun turrets were 65 percent AP, 25 percent incendiary and 10 percent tracer (two-gun turrets had 20 percent tracer with the others reduced accordingly.) Between 1942 and 1944 the approved sequence was 70 percent AP, 20 percent incendiary and 10 percent tracer. This was modified in May 1944 to increase the proportion of incendiary to 20-30 percent, and changed again just before the end of the war to 100 percent incendiary, on the grounds that the German fighters were too heavily armoured for rifle-calibre AP to have any effect, whereas incendiaries at least stood a chance of setting light to something. Fixed .303 in guns for air fighting were loaded 50 percent AP and 50 percent Incendiary; for attacking ground targets the figures changed to 75 percent AP, 25 percent Incendiary. The .303 in Mosquito FB nose guns were loaded with unmixed belts of AP and incendiary rounds; i.e. two guns fired only AP, two only incendiaries (this also appeared to be standard practice with Spitfire .303s). The few .50 in Brownings used in Bomber Command (initially only in American-made aircraft) also saw changes in the loading sequence, from 40 percent AP, 40 percent Incendiary and 20 percent tracer in 1942, to 60 percent AP, 20 percent incendiary and 20 percent tracer in early 1944. Spitfires equipped with the .50 in used 50 percent each of AP and incendiary rounds until the M8 API became available, when that was used exclusively.

The Luftwaffe saw considerable variations in belt loading, as follows:

The 7.92mm MG-17 used in fighters were loaded with 50 percent AP, 40 percent API and 10 percent HEI (a Beobachtungsgeschoss, or observation round, which exploded on impact to show the pilot he was on target). For ground attack and for the MG-15 and MG-81 felxible guns, the sequence typically changed to equal proportions of AP, AP-T and API; v-munition loadings were only used in the MG-17. The 13mm MG-131 was loaded with one or two HEI for every AP/T. Official loadings for the 20mm belts and magazines varied at different times and places. Three types of projectiles were usually mixed in the belts: HEI (M-Geschoss), HE/T and AP/API or APHE. Ratios quoted include 1:1:1, 3:1:1, and 2:2:1 respectively.

Generally speaking, the more powerful weapons were able to provide sufficient destructive power with only one or two projectile types, so belts were less varied. As we have seen, an equal mix of HEI and SAPI became standard in the RAF's 20mm Hispanos, whereas the 30mm MK-108 principally relied on the M-Geschoss HEI it was designed for. The .50 in Browning fighter belts in US service started the war loaded with 40 percent AP, 40 percent Incendiary and 20 percent tracer. The tracer fell out of favour when it was realised that it was providing more help to the enemy. By the end of the war, fighters were primarily loaded with the M8 API (which appeared in service in spring 1944), as this proved to be a good general-purpose projectile, although the M23 incendiary also saw some use.

Some fighter pilots loaded the last section of their belts with tracer, to give them a warning that they were close to running out of ammunition (round counters not being commonly used, or at least looked at during combat). However, the enemy soon realised this and could turn it to their tactical advantage."

And thats the brief section on that. Quite interesting to say the least. If anyone has any questions as to what the different symbols mean, I can answer them. For example, SAPI = Semi-Armour Piercing Incendiary, HEI = High explosive incendiary. Cheers.

TeaWagon

p1ngu666
08-09-2005, 08:30 AM
some VIII pilots in burma changed to have a burst of tracer early in teh belt, japanease would think there low on ammo... which ofcourse they wherent and would surprise the japanease http://forums.ubi.com/images/smilies/59.gif

Kocur_
08-09-2005, 10:14 AM
TeaWagon! Thank you very, very much!
Finally I have those beltings http://forums.ubi.com/images/smilies/25.gif
Wish I had the book too http://forums.ubi.com/images/smilies/16x16_smiley-sad.gif

Kocur_
08-09-2005, 10:45 AM
I have two questions:

1.What does "semi" in "SAPI" mean? Is related to explosive materiel in the projectile, not only Incendiary?
2.Does the book include SAPI effectiveness calculated with Henning Ruch method, like here, down the page:
http://www.quarry.nildram.co.uk/WW2guneffect.htm

TeaWagon
08-09-2005, 12:55 PM
Kocur:

1) Glad I could help. You can order the book through Barnes & Noble or Borders Book Store. I personally special-ordered through Borders, it arrived within a week with free shipping, though the book itself cost 50 U.S. Dollars.

2) "Semi" in "Semi-Armour Piercing Incendiary" means this particular bullet's penetration power has been reduced compared to a normal AP round. This is because chemical material that is used as incendiary, high explosive, or tracer material is lighter than an otherwise solid-steel and is meant for a different purpose; burning or exploding rather than penetrating. So in effect, the SAPI round is a mixture of incendiary material and the original (but smaller) solid steel core, sacrificing some penetration power for chemical power, and this seemed to have been generally considered a good trade-off considering the increased effectiveness against the fuel tanks, ammunition stores, and any other flammable material inside an aircraft.

3) No it does not contain this revised method, apparently the Henning Ruch revised method of calculation was amended onto William's website at a date later than when his book was first published.

If anyone else has something valuable to contribute or questions to ask, please. I'll try to be as helpful as I can. Again, I seriously recommend purchasing this book if you are interested in the subject.

TeaWagon

Kocur_
08-09-2005, 01:11 PM
Rgr on SAPI.
The hard core is usually simply shorter, and rest of space under jacket is used to contain chemical material. Since we have "SAPI" for BH Mk.II and "API" for M2 I thought that "Semi" meant further difference to API, i.e. even shorter penetrator for, say explosive sourrunded with incendiary material. But I understand that British were simply more honest in naming projectile to both penetrate and light http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif
Or differnce in penetrating performance between .50BMG AP and API was smaller than for BH AP and SAPI.
Thx again!

LBR_Rommel
08-10-2005, 07:24 PM
S!

TeaWagon ty for your post, very good job TeaWagon, because you gave us info about gunnery, btw a subject cause of some major discussions around this place, reseach based on books is always bring rich info, instead of some internet sites, some easy to make just to bring wrong info to players, just few websites have consistent info.

Your post TeaWagon is jewel, plz bring us more if possible.

<O|

TeaWagon
08-11-2005, 08:13 AM
Glad I could make a contribution. Also, another interesting thing of note... As so humorously mentioned in your signature picture there, as it relates to the Spitfire...

From Page 96... Quote.

"But in August Supermarine had perfected a more reliable installation of the cannon with an improved feed mechanism, and from October onwards No. 19 received several aircraft that had been modified to take advantage of this new development. These Spitfires also retained four .303 in guns in the outer wing panels. Their guns had to be set to converge at 300 yards, because the mountings of the cannon could not be sufficiently adjusted to make them converge at a shorter distance."

Unquote. This exert is talking about the first Spitfires mounted with the 20mm Hispano cannons in the year 1940. Apparently they could not be set to converge below 300 yards... Which converted to metric, is about 274 meters.

Certainly this is what I'll be changing my cannon convergence to in the Spitfire to retain historical accurary... Even if it will substantially hurt my aerial accuracy. All the more fun in learning how.

Also note how the first cannon armed Spitfires were too late and came in too few numbers to make any meaningful impact upon the Battle of Britain itself. Unfortunate, for those cannons would most certainly have made shooting down german bombers considerably easier, I'm sure.

TeaWagon

TeaWagon
08-13-2005, 06:40 PM
Interesting note here not related to the book... Was talking to a Finnish friend about the Spitfire convergence issue, and he said he had a diary of an RAF pilot and that the Spitfire variant he flew (Spitfire Vb, apparently) had a new mounting which allowed the cannons to be converged all the way down to 150 meters.

This would obviously be quite beneficial, but is not exactly conclusive evidence. I'll be sure to ask him about it later when I see him.

Has anyone else have any other interesting evidence, test-data or otherwise, stating curious facts on weapon convergence or ballistics?

TeaWagon