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Japanese 40MM?

 
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Japanese 40MM? - 11/5/2012 3:52:17 PM   
John 3rd


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Does anyone know if the Japanese ever did testing into any form of more useful smaller AA weapon like the 40MM that became standard for the USN?


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RE: Japanese 40MM? - 11/5/2012 5:03:50 PM   
JuanG


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40mm/62 Type 91 was in service till mid 30s.

The Japanese were working on a Bofors derivative termed the 40mm/60 Type 5 at the end of the war, based on a captured British peice.

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RE: Japanese 40MM? - 11/5/2012 5:40:47 PM   
John 3rd


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Hey Juan! Hope you're well.

Why didn't they use it on board ships? Was the Type 91 useful or a problem?

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RE: Japanese 40MM? - 11/5/2012 6:50:04 PM   
JuanG


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quote:

ORIGINAL: John 3rd

Hey Juan! Hope you're well.

Why didn't they use it on board ships? Was the Type 91 useful or a problem?


Im doing fine, thanks John.

Type 91 was retired due to poor rate of fire and muzzle velocity, and replaced with 25mm Type 96.

More info on the weapon here; http://www.navweaps.com/Weapons/WNJAP_40mm-62_HI.htm

Type 5 was not ready by the end of the war if I remember correctly.

< Message edited by JuanG -- 11/5/2012 6:52:36 PM >


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RE: Japanese 40MM? - 11/5/2012 9:14:23 PM   
Natali

 

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I have seen much same info as JuanG. It specs a lot like a Vickers 2prd Mk II that only used the Low Velocity round, with the MV of 1900 fps vs the HV with 2300 fps and 2800 fps for the Bofors. It chewed at maybe 70rpm, while the Brit version went to 100rpm with the interrupter gear and the Bofors went to 120-140rpm (effective, not cyclic).

Japan had like scads of these. Bought 500 from UK and ripped off maybe 1000 more. Apocryphal info from Axis weapon fansites supposes they were pushed off on the IJN that assigned them to land AA defense. Since many Japanese and US OOB show SNLF defense units with 40mm guns and ther's pictures of them everywhere, it makes some sense.

[ed] everything I seen says they got pulled off ships in 1935 as quick as the 25mm multi-mount got available.

Simple mv(squared) and rof between the T91 40mm and the T96 25mm gets my vote for the 25mm. Been yelling at JWE about the specs between these two for a long time. Let's see. Important to me because of my SNLF definition work.

< Message edited by Natali -- 11/5/2012 9:23:25 PM >

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RE: Japanese 40MM? - 11/7/2012 11:25:54 PM   
el cid again

 

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The Japanese designed a late war PC assuming the 40 mm single would be its main battery.

The Type 03 was long delayed and just entering production when the war ended, and quality by
the was very poor. Much of the delay was due to minor modifications to "improve" the design,
the longer bbl for example slightly increasing muzzle velocity, altitude and range. Higher priority
might have put it in service by mid 1943, and more sensible industrial policy might not have
diluted the workforce of skilled labor in the latter part of the war. Might have beens are hard to
do well.

In strictly historical scenarios, I assume the single 40 mm Type 03 can replace a triple 25 mm mounting
on vessels upgrades after the end of the historical war - from 9 45 on. In non-strictly historical
ones, I assume this from 7/43. I do not allow the use of multiple mountings on the basis none were
ever developed and, due to resource limitations, probably would not be developed. Even so, it
offers an important enhancement to AAA, one not entirely obvious in game terms. [Medium AAA is
effective in the gap between light AAA and heavy AAA in altitude terms]

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RE: Japanese 40MM? - 11/8/2012 4:07:58 AM   
PaxMondo


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John,

In one of your RA design threads, there was a really good discussion on AA.  Here are some of the highlights:

The first problem for IJ is that any small caliber, aimed AA had to be man-served.  IJ had neither the technology nor the industry to build auto-served weapons.  This puts a real limit on gun weight ... past a couple of hundred pounds, you can't turn the mount fast enough to track an aircraft.  There were several IJ analyses recovered after the war that stated even the 2x25mm mounts were too big and couldn't track the USN aircraft, they needed to stay with single mounts.  The triple mounts used on the Yamato were supposedly completely ineffectual.

Second was the reloads.  The 25 mm used cases that held something like 20 rounds each.  The limit on the rounds was due to weight to get them in and out quick enough.  They never really developed a good belt feed system.  Why is really good question, and one that I have never really answered to my satisfaction.  My current thinking is simply administrative obstacles ... they couldn't agree on a final design and so it never got done.  Who knows.  40mm would greatly aggravate this issue.  Like auto-servors, I don't see the IJ industry of the 40's able to supply auto-feeders like the allies in the quantities that we are talking about for small caliber AA.

Third was barrel replacement and life.  The 25mm wasn't a bad design, but the barrel replacement wasn't all that quick (the numbers I typically ran across were about 10 mins.   For such a small weapon, that's not too quick.  Scale this up for a 40mm ...

Fourth was stability.  The man powered mounts had to be light to move, but this also meant they flexed during firing adding skew to the aim.  Vibration was also a problem.  IJ made several changes to address this as the war progressed and more in the works at war's end.

Fifth was targetting.  Sighting was rudimentary by allied standards.  Going to a 40mm with longer range would only exacerbate this issue.  They had technology to improve this, but had made little progress in doing so by wars end.  Again, I have not really gotten a good reason on this.

Likely there were more issues, but these are the ones I have uncovered in my studies on this.  My conclusion from this was that an effective 40mm weapon for the IJ was a pipe dream.  Wisely, this was not pursued and implemented to any great extent as it would have degraded what AA they did have. 

Opinions will likely vary on this, as they do on most things. 

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RE: Japanese 40MM? - 11/8/2012 3:56:36 PM   
el cid again

 

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Actually,
IJN developed a superior system of mounting, sighting and fire control computers
(these were unique and had a name that doesn't translate well into English at all)
for use with the new, Type 38, 100 mm guns. It was also used by the new, high
peroformance Type 38 76 mm guns, which (too bad for them) were not produced
in quantity (one battery ashore at Maizuru, otherwise only on Agano class cruisers,
for which they were designed). The same system (with different ballistic cams)
would also be used with the Type 1 (or Type 5) 127 mm - had it entered service
(only one prototype gun was used - but it was a superior 51 caliber gun - far more
successful than the comparable USN 54 caliber creatures of late war and post
war design). There is no reason in principle a mounting for multiple 40 mm (up
to quad) could not have adaped this system.

As for the 25 mm triple being effective, it is similar to the DP guns of all calibers
used by Japan - or most of them. Many Japanese guns had AA shell, and under
two circumstances they could be used effectively:

1) The ship had to be on a strait course (not using the standard circular maneuver
of IJN when subject to air attack) to yield a stable platform

2) The target aircraft had to be on a closing bearing - what in naval parlance is termed
"constant bearing decreasing range" - or close to it.

Perhaps the most famous example of this is Takishi Hara's defeating of skip bombing -
something almost always fatal to a Japanese ship. Never mind his guns were not
suitable for rapid training or changes in elevation - he had been thinking about the problem
ever since he heard of it. When he saw the bomber's approach, he realized it needed
to stay on course to have a predictable bomb flight - and also that it would assume in its
offset that he was using the standard maneuver. So he ordered a strait course - which
confused his crew - and gave his gunners a steady platform. They were experienced,
and never mind his ship did NOT have the modern fire control system on the AA destroyers,
they fatally damaged the bomber. He got a bonus - on its way in the bomber reported by
radio he was hit! Seems going to full speed set creosote in his stacks on fire, causeing
flame and black smoke, and the bomber interpreted that as a bomb hit! [See Japanese
Destroyer Captain, now in reprint in hard bound form by USNI]

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RE: Japanese 40MM? - 11/8/2012 7:05:21 PM   
US87891

 

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quote:

ORIGINAL: PaxMondo
John,

In one of your RA design threads, there was a really good discussion on AA.  Here are some of the highlights:
...

I think you might be onto something, John 3rd. The Type 91 was retired from Japanese service because of percieved rof and velocity issues. The Brits had the same issues with the same gun, but their solution was different. They went for quad/octuple volume, using hydraulics.

That solution wasn't the quite best, so they developed a different, high velocity, round that would help things out a bit. The Japanese never even thought about this, and went ahead with the Vickers 40mm like a slice of Hamachi sashimi. Coulda, shoulda, woulda, you bet your bippy.

Brits came up with HV shells for those guns. And multi-multi-mounts. And they got to within a skoosh of what the US was doing with the Bofors.

Pm coming your way.

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RE: Japanese 40MM? - 11/8/2012 8:53:06 PM   
Capt. Harlock


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quote:

IJN developed a superior system of mounting, sighting and fire control computers
(these were unique and had a name that doesn't translate well into English at all)
for use with the new, Type 38, 100 mm guns. It was also used by the new, high
peroformance Type 38 76 mm guns, which (too bad for them) were not produced
in quantity (one battery ashore at Maizuru, otherwise only on Agano class cruisers,
for which they were designed). The same system (with different ballistic cams)
would also be used with the Type 1 (or Type 5) 127 mm - had it entered service
(only one prototype gun was used - but it was a superior 51 caliber gun - far more
successful than the comparable USN 54 caliber creatures of late war and post
war design). There is no reason in principle a mounting for multiple 40 mm (up
to quad) could not have adaped this system.


It seems to me there was one very good reason: Japanese industry did not have the capacity to turn out the number of powered mounts that would have been needed. To take the case of the Agano, she would have needed eight powered mounts for her 25mm weapons in bunches of four. (The Yamato would have needed forty.) The type 38 100mm was indeed a great gun, but only a little over 200 were ever built.

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RE: Japanese 40MM? - 11/8/2012 11:23:51 PM   
PaxMondo


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quote:

ORIGINAL: Capt. Harlock

[It seems to me there was one very good reason: Japanese industry did not have the capacity to turn out the number of powered mounts that would have been needed. To take the case of the Agano, she would have needed eight powered mounts for her 25mm weapons in bunches of four. (The Yamato would have needed forty.) The type 38 100mm was indeed a great gun, but only a little over 200 were ever built.

Exactly.

And the triple 25mm, the mount could not be moved fast enough to track many/most oncoming aircraft. This was also true of many of the IJ DP's. They were too slow to be effective. I think the stock numbers used for them are quite 'generous'.

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RE: Japanese 40MM? - 11/14/2012 12:42:26 PM   
FatR

 

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quote:

ORIGINAL: John 3rd

Hey Juan! Hope you're well.

Why didn't they use it on board ships? Was the Type 91 useful or a problem?

Type 91 was unreliable, and lacked in accuracy and range due to low muzzle velocity (although its in-game stats are uber). British barely managed to make the same Vickers design somewhat effective by placing guns into massive 8-gun mounts and equipping them with late-war Allied advances in fire control.

A few Type 5 guns were installed on board of some smaller shipsconstructed at the end of the war, for example:
http://www.navypedia.org/ships/japan/jap_ml_kamishima.htm

The problem was general inability to produce these guns in numbers, due to their complexity (US version of Bofors 40mm was heavily modified to become suitable for mass production) and overall lack of resources for production of such relatively costly and complex weapons by the end war (indeed, every country except USA and, to an extent, Germany, had severe troubles with mass production of automatic AA cannons during WW II, at that day it was cutting-edge technology).

Take note, that Japan wasn't able to produce even 25/60 Type 96 in sufficient numbers until well into 1944 - if at the beginning of the war USN's automatic AA armament was at best equal in numbers and calibre to IJN's (inferior on many classes, that still carried only 12.7 MGs), by May of 1942 USN achieved massive superiority in numbers of automatic flak guns (you can take a look at my little calculation for the Battle of Coral Sea in the Perfect War thread).

That's why I was agaist adding more 40mm flak guns to Japanese in RA, of course.

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RE: Japanese 40MM? - 11/14/2012 12:58:16 PM   
FatR

 

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quote:

ORIGINAL: PaxMondo

John,

In one of your RA design threads, there was a really good discussion on AA.  Here are some of the highlights:

The first problem for IJ is that any small caliber, aimed AA had to be man-served.  IJ had neither the technology nor the industry to build auto-served weapons. 

This is incorrect. 25mm mounts on major warships, at least their initial pre-war and early-war installations, were not only powered, but trained on target by input from a fire director. At the moment of its initial acceptance for service this was pretty much the most advanced small-calibre flak system in the world. The problem was that gun motors lacked power and methods of fire direction were too slow to reliably track late-war aircraft. And most of the gun mounts added in late-war upgrades were manually operated. Also, 25mm single mounts had only a primitive ring sight. So not only Japanese small-calibre AA weaponry only got enough numbers by mid-to-late 1944 (and even then, only on warships and the most valuable transports, average cargo haulers remained relatively underarmed), technically it actually degraded below 1941's level.

Regardless, I note that Japanese flak should not be blamed for failing to do the impossible and not protecting the fleet against massed air attacks on its own.


< Message edited by FatR -- 11/14/2012 1:03:52 PM >


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RE: Japanese 40MM? - 11/14/2012 1:10:29 PM   
PaxMondo


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quote:

ORIGINAL: FatR

quote:

ORIGINAL: PaxMondo

John,

In one of your RA design threads, there was a really good discussion on AA.  Here are some of the highlights:

The first problem for IJ is that any small caliber, aimed AA had to be man-served.  IJ had neither the technology nor the industry to build auto-served weapons. 

This is incorrect. 25mm mounts on major warships, at least their initial pre-war and early-war installations, were not only powered, but trained on target by input from a fire director. At the moment of its initial acceptance for service this was pretty much the most advanced small-calibre flak system in the world. The problem was that gun motors lacked power and methods of fire direction were too slow to reliably track late-war aircraft. And most of the gun mounts added in late-war upgrades were manually operated. Also, 25mm single mounts had only a primitive ring sight. So not only Japanese small-calibre AA weaponry only got enough numbers by mid-to-late 1944 (and even then, only on warships and the most valuable transports, average cargo haulers remained relatively underarmed), technically it actually degraded below 1941's level.

Regardless, I note that Japanese flak should not be blamed for failing to do the impossible and not protecting the fleet against massed air attacks on its own.


I think you just agreed with me, even though your opening says you do not. Thanks.

Yes, they had servo powered. Yes they didn't work (too slow) and they couldn't build enough of them anyway. Yes they went to man operated. Yes multi-gun platforms were too heavy to train with manpower. Yes they had lousy sighting. Yes, by wars end what they were deploying was not good.

They did have a number of fixes for all of this, but they never got them deployed in any significance before there was no fleet to deploy them to.

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RE: Japanese 40MM? - 11/14/2012 3:51:06 PM   
btbw

 

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I see many people trust in myth of low ROF or slow track of 25mm AA gun. Well winners always right.
But in really this not real problem of that gun.
Feeding? Almost all guns compared by caliber feeded like 25mm gun.
Tracking? Same ****.
Unstable during fire? Same **** as chigaco piano or Oerlikon - mounts with manual direction never can compensate good enough as automatic mounts.
But real problem of 25mm gun only one - WEAK.
When this gun developed planes looks like Swordwish - paper planes with low speed and alt. So 25mm gun was good enough for strike that targets.
But in first year of war situation greatly changed.
So 25mm gun with current ROF and track ability start to lose battle of speed and damage.
Main target for light AA it stop plane from drop their ordanance.
When it was pilot sitting on string bag - 25mm work good enough. When pilot hide after armour - then planes start penetrate AA defense and hurt ships.
So 25mm gun lose battle with very weak result of summing - ROF+ damage + range + track. If 25mm gun can shoot faster and much more far or produce better damage then it can equal chances.
Japanese tried raise ROF with multiple barrles. But that solution was not enough without redo feeding system. I mean not clip size, but clip feeding when barrle can eat shells from a few sources or clip current used can be refilled with another clip. But outdated hierarchy system dont give that signal from users to developers.
When problem understanded Japan already cannot produce nothing good because all work hands become to Army.
So please forget about MYTHS. Problem of 25mm gun same as for all light AAs and complexity without real loses in ROF or track or feed.
No one light AA gun was not good. You can fap on Oerlikon or Pom-pom but that guns in really was psihological weapon mostly especially if Japan dont make paper planes (for better range, maneur etc).
P.S. You can also add change of tactic. When 25mm fight against planes with 7/13mm MG which they even dont used - it like practice shooting. When Yamato sunk (and you can good see it in movie) all planes used all guns and even rockets for suppress light AA - then you must hit enemy plane first. Before he start zig-zag or shoot your with their MGs.
All dudes which think AA gun cannot track plane (if we talk about 25mm of course) must start learn geometry. On range like 1-2km zigzag with 50m legs give how much degree change?
Just for info - how much planes lost (with their types) during sinking Yamato?

< Message edited by btbw -- 11/14/2012 4:07:58 PM >

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RE: Japanese 40MM? - 11/15/2012 11:36:13 PM   
JuanG


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Not even going to attempt to answer the majority of that, just the technical bits.

quote:

ORIGINAL: btbw
I see many people trust in myth of low ROF or slow track of 25mm AA gun. Well winners always right.
But in really this not real problem of that gun.
Feeding? Almost all guns compared by caliber feeded like 25mm gun.

25mm Type 96 - 15 round magazine per gun, meaning 3.75 seconds of fire (240rpm cyclic). Could not be loaded/fed until the whole magazine was exhausted.

1.1in Mark 1 - Two 8 round clips per gun, meaning 6.4 seconds of fire (150rpm cyclic). Fed from one clip at a time, so sustained fire was possible by staggering fire and good loading.

2pdr Mk VIII - 14 round belts; feed box could hold 4, 8 and 10 belts per gun for the single, quad and octuple respectively. This is 84 seconds of fire for the octuple (100rpm cyclic) and more for the smaller mounts. Could not be loaded/fed until the whole feed box was exhausted, and was the hardest of the weapons here to load.

20mm Oerlikon - 60 round spiral magazine, meaning 8 seconds of fire (450rpm cyclic). Could not be loaded/fed until magazine was exhausted, though there was a proposed belt fed version. Reloading was fast.

40mm Bofors - Two 4 round clips per gun, meaning 4 seconds of fire (120rpm cyclic). Could be easily fed while firing, allowing for uninterrupted fire for the duration of an engagement (unless the ammo team messed up).

FEEDING MECHANISM LOSER? 25mm Type 96, by a long shot.

quote:

ORIGINAL: btbw
Tracking? Same ****.

25mm Type 96 - Triple; Elevation 12 degrees per second when powered, less when manual (which most were). Train 18 degrees per second when powered, notably less when manual.

1.1in Mark 1 - Elevation 24 degrees per second, Train 30 degrees per second.

2pdr Mk VIII - MkVII manually operated quad Elevation 15 degrees per second, Train 15 degrees per second. Powered mounts, Elevation 25 degrees per second, Train 25 degrees per second.

20mm Oerlikon - Manual only. Train and elevation rates rather high due to relatively lightweight single mounting. Twin mounts were notably less mobile.

40mm Bofors - Twin and Quad; Elevation 24 degrees per second, Train 26 degrees per second.

TRAIN/ELEVATION GEAR LOSER? 25mm Type 96, even when in its powered version. Twin 20mm and manual 2pdr were only slightly better, but everything else leaves this thing in the dust.

Was it also the weakest of the lot? Yes, both in terms of muzzle kinetic energy and actual explosive load. But even if it had packed the power of a 40mm behind it, the weapon is useless if you aren't going to hit anything with it or can't sustain fire. This last bit is really important when hitting flying targets with an impact fuzed automatic weapon, especially in the absence of radar assistance.

< Message edited by JuanG -- 11/15/2012 11:41:41 PM >


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RE: Japanese 40MM? - 11/16/2012 4:40:48 AM   
PaxMondo


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quote:

ORIGINAL: JuanG

... Was it also the weakest of the lot? Yes, both in terms of muzzle kinetic energy and actual explosive load. But even if it had packed the power of a 40mm behind it, the weapon is useless if you aren't going to hit anything with it or can't sustain fire. This last bit is really important when hitting flying targets with an impact fuzed automatic weapon, especially in the absence of radar assistance.


And of course if they couldn't get the 25mm to train or elevate fast enough, the 40mm would have been just that much worse. Ergo, a 40mm solution was just never in the cards.

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RE: Japanese 40MM? - 11/16/2012 5:07:34 PM   
Natali

 

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Not even counting any of that, the 25mm T96 was not good at gun ballistics numbers either, the 40mm T91 was even worse. This is from an equation I got from somebody and it uses the ballistics numbers from NavWeaps.com. It’s only baby steps because it uses the “normal practical” rof and doesn’t take any of the other bad things into account but it’s a wicked eye-opener anyways. Looks like T91 and T96 were both almost as good as a 20mm Oerlikon. The 40mm T91 was based on the Vickers 2pdr gun with the LV ammo. The gun needed a different breech for the HV ammo, it wasn’t interchangeable. The Japanese never redesigned for HV ammo.

25mm/60 T-96 : 194 kilojoules/barrel/second
40mm/62 T-91 : 187 kilojoules/barrel/second

2pdr/39 QF Mk-VIII, LV : 252 kilojoules/barrel/second
2pdr/39 QF Mk-VIII, HV : 386 kilojoules/barrel/second

20mm/70 Oerlikon Mk2 : 202 kilojoules/barrel/second
1.1”(28mm)/75 Mk1 : 228 kilojoules/barrel/second
40mm/56 Bofors Mk1 : 699 kilojoules/barrel/second

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RE: Japanese 40MM? - 11/16/2012 5:37:58 PM   
Natali

 

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I won my argument with JWE! He sent me his equations for calculating and the equations for fitting into the game. The 40mm T-91 HI Shiki doesn’t fit at all and the UK 40mm guns are generous. He didn’t spend a lot of time on AAMGs and AAMCs but just moved datapoints to append them onto the game curve.

If he gave the Japanese the true accurate values they would well and truly suck and people would complain even worse, so he avoided the hassle by just sticking them on the mm curve.

I have a few equations that go to the same place and are consistent with the game fitting equations and with Babes. JWE likes them and says “go for it”!!! So, without further adoo, here is what I suggest for mods that want to use the 40mm T-91. I would make them identical to the 25mm T-96:

Acc-47
Eff-22

Since the 25mm has more ammo and is easier to reload, that slants the choice to the 25mm, just like the Japanese did.

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RE: Japanese 40MM? - 11/18/2012 10:14:38 AM   
inqistor


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quote:

ORIGINAL: JuanG

25mm Type 96 - 15 round magazine per gun, meaning 3.75 seconds of fire (240rpm cyclic). Could not be loaded/fed until the whole magazine was exhausted.


According to British 1940 research, 25mm would use around 30 rounds per engagement. This is just ONE reload, so not that big deal (of course other guns would need NOT to stop firing, so they are better). Also, they were air cooled, so not expected to fire for long time anyway.

quote:

25mm Type 96 - Triple; Elevation 12 degrees per second when powered, less when manual (which most were). Train 18 degrees per second when powered, notably less when manual.


This is data for firing, triple mount. Since engine could work only for 3 minutes for full load, and continuous for empty guns (10 minutes for half load), I am guessing it could train faster when not fully loaded.
Anyway single-mount was free swinging, so hardly any difference with Oerlikon.

Also - 25mm had highest muzzle velocity of them all (900 mps)




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RE: Japanese 40MM? - 11/18/2012 12:11:59 PM   
btbw

 

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quote:

ORIGINAL: JuanG
25mm Type 96 - Triple; Elevation 12 degrees per second when powered, less when manual (which most were). Train 18 degrees per second when powered, notably less when manual.

1.1in Mark 1 - Elevation 24 degrees per second, Train 30 degrees per second.

2pdr Mk VIII - MkVII manually operated quad Elevation 15 degrees per second, Train 15 degrees per second. Powered mounts, Elevation 25 degrees per second, Train 25 degrees per second.

20mm Oerlikon - Manual only. Train and elevation rates rather high due to relatively lightweight single mounting. Twin mounts were notably less mobile.

40mm Bofors - Twin and Quad; Elevation 24 degrees per second, Train 26 degrees per second.

TRAIN/ELEVATION GEAR LOSER? 25mm Type 96, even when in its powered version. Twin 20mm and manual 2pdr were only slightly better, but everything else leaves this thing in the dust.


So nice to compare LIGHTWEIGHT mount with HEAVY!
What about same type of mounts in your comparision?
25mm Type 96, 2pdr Mk VIII and 20mm Oerlikon have same turn rate. So why all repeat bullshit about slow Jap LAA? It same as Allies analogs, which widely used during WW2. Of course if you can place mount 5-10t weight then you UBER. But you cannot place so much mounts for cover all directions at once - it why very fast turn rate is necessary.
Again, problem of 25mm not in turn rate. Low caliber gun for middle-end stage of war without upgrade.
Try compare firing ability from same displacement ship with different mount types (and different number of them depending from eating weight).
Another thing is Air Superiority. How many planes can attack Bofors-equipped ships and how much planes attacked 25mm flak equipped ships? How many planes will shoot down Bofors if ship attacked with few hundreds planes which coming from all directions and bring rain of bullets on your completely undefended gunners?



< Message edited by btbw -- 11/18/2012 12:19:42 PM >

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Post #: 21
RE: Japanese 40MM? - 11/18/2012 1:09:28 PM   
PaxMondo


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quote:

ORIGINAL: inqistor

...Also, they were air cooled, so not expected to fire for long time anyway.


Which is a major contributing factor in their (relatively) short barrel life.

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RE: Japanese 40MM? - 11/18/2012 1:27:09 PM   
btbw

 

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quote:

ORIGINAL: PaxMondo


quote:

ORIGINAL: inqistor

...Also, they were air cooled, so not expected to fire for long time anyway.


Which is a major contributing factor in their (relatively) short barrel life.

Many flaks is air-cooled, but jap flak is weird? Barrel life dont affect on defense against air raid. It problem of replacements. ALot of guns with high value characteristics have low barrel life but dont count as bad. We cannot raise velocity without lose service rate.
What is really bad - CALIBER. No 37-57mm replacements which raise effective range/alt and one-shot destruction. Lesser range - lesser time for fire, more casualties from planes weapon. Lesser one-shot destruction power - more shots needed, more time etc.

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RE: Japanese 40MM? - 11/18/2012 2:19:02 PM   
inqistor


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quote:

ORIGINAL: PaxMondo


quote:

ORIGINAL: inqistor

...Also, they were air cooled, so not expected to fire for long time anyway.


Which is a major contributing factor in their (relatively) short barrel life.

It does not seem barrel life was that short (not, that they actually checked it). What I find interesting here, is text about director, which loses accuracy, when speed falls too low, so obviously it was not THAT primitive device.




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Post #: 24
RE: Japanese 40MM? - 11/18/2012 4:13:50 PM   
btbw

 

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quote:

ORIGINAL: inqistor
It does not seem barrel life was that short (not, that they actually checked it). What I find interesting here, is text about director, which loses accuracy, when speed falls too low, so obviously it was not THAT primitive device.

Winners always RIGHT. Most historic data written almost after victory. When Japs called monkeys.

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Post #: 25
RE: Japanese 40MM? - 11/18/2012 4:29:49 PM   
PaxMondo


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quote:

ORIGINAL: inqistor

quote:

ORIGINAL: PaxMondo


quote:

ORIGINAL: inqistor

...Also, they were air cooled, so not expected to fire for long time anyway.


Which is a major contributing factor in their (relatively) short barrel life.

It does not seem barrel life was that short (not, that they actually checked it). What I find interesting here, is text about director, which loses accuracy, when speed falls too low, so obviously it was not THAT primitive device.





Yeah, I read this summary analysis. But somewhere here <searching, but not yet found> I've some IJ docs describing that in the field they found the barrel life to be somewhat short. Now, there are a lot of reasons for this and of course 'somewhat' is subjective. I'll throw out a few that come to mind, that would be consistent with the Naval Intel doc you are quoting:

1. Inexperience of operators. Firing too long of bursts
2. Lack of guide to state rounds to replace by.
3. Lack of round logs.

Remember, the 25mm was the standard (one of the very few) across all services and disciplines. The docs that I have around here somewhere are derived from feedback from land based units ... can't recall if they were IJA or IJN units though. They are an internal assessment of the 25mm along with recommendations of what/how to address the raised issues. On a ship, the 3rd one is less likely to occur. Land based units ... They also call out the difficulty of reloading the cannisters, reloading the guns with the cannisters, vibration issues, ....




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RE: Japanese 40MM? - 11/18/2012 5:22:35 PM   
sandman455


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Whoa!
Here I was thinking I had a good grasp on the principal theories behind anti-aircraft guns. Then I read a couple posts have me scratching my head.

First off, I strongly suggest you some guys dive into this document if you haven't already before:

http://www.history.navy.mil/library/online/Antiaircraft_Action_Summary_wwii.htm#III

This document spurred many other tactical documents that will never be declassified. Some of the conclusions contained within it are off the mark but the data being presented is most telling about the nature of engaging aircraft with hot flying lead. Pay very close attention to the charts located in the back.

To address some of your posts:

Not sure why you'd be interested in the time between reloads on any AA gun? Besides, I'm sure at least 1 or 2 of the guns you've listed can vary their rate of fire (ROF). Only the EFFECTIVE cyclic rate (the theoretical is worthless) of an AA gun is really relevent and that's only in certain engagements (ie a missile or an Kamikaze). For these engagements the logical is simple enough; as the targeting problem gets simplified the necessity to keep shooting is clear. However, keep in mind the gunner (the person aiming and firing) doesn't do the reloading. His job performance has little to do with rounds/time per clip. He must train the gun effectively and cares little about whether the gun is shooting or not in this kind of engagement.

After WW1 the ROF of a gun ranked high on the list of preferred stats. After WW2 it had fallen off a good bit. Many manufacturers had already discounted it somewhat even prior to the start of the conflict and usually regretted their decision since their buyers hadn't gotten the memo yet. The reasons ROF took a hit was that there were plenty of reports showing that the target was usually hit within the first second or two of fire for light weight, high ROF weapons. After this many factors (barrel temp, vibration, gunner concentration, target track) came into play that seriously degraded the gun's accuracy.

The swing and train rate and whether the gun was powered: This is a useful stat but only under certain conditions and most are limited to shore base batteries. These guns often suffer with having a very limited target acquisition and fire time. The ground and its many obstructions help the strikers immensely if they opt to transit the area at low altitude. As aircraft got faster and faster, this time got shorter and shorter. Swing and train rate became real issues. Ship at sea engagements don't usually afford (clouds would help) strike aircraft this luxury. Only escort ships would have much issue with it and as the data suggests, they didn't hit much when they were presented with real swing/train rate requirements. The irrelevence of swing/train rate is clearly born out if you look at the charts in the back of the document I linked. Those 5"/38's weren't worried about it because you simply can't hit aircraft very reliably if you are forced to move your barrel much.

Analyzing the joules per second of a AA gun? Not sure if that qualifies as ballastics. Novel idea I guess, but it completely negates the imperative issue of having to hit the target. It is after all the MOST important issue. And because of this the true ballistics (as normally defined, check wikipedia) of a gun is the #1 stat in gauging the accuracy and effectiveness of said gun. The higher the velocity, the heavier the round the more likely you will hit the target with an aimed shot. It is supported by every single document I've ever read regarding not only AAA but shooting in general.

Again, I seriously suggest everyone reread the linked document and think about it. Look and digest those charts towards the back. Especially the siginficance of the mission profile of the aircraft, the placement of the AA gun with reference to being on the target ship or on the escort. Even the category "Fast Carrier TF" over compared to "Other ships - Philippines" is eye opening if you grasp the notion that a "Other ship" is really a situation of an unescorted target ship.

Then remember this document pertains ONLY to the USN. The AA issues of the USN do not match up well with the AA issues of the IJN especially after 1944. For one, they held very different tactical doctrines with regard to TF ship deployment. The IJN favored maneuverability over close in AA support. Probably because they feared torpedoes above all else. Pretty logical when you consider their torps worked rather well. Yet this tactical doctrine was at the detriment to DB attacks where concentrating heavy AA around the high value unit was the best way of disrupting the DB's performance. Given the poor quality of USN torpedoes it is clear that the IJN would have been better off adopting the USN CVTF deployment doctrine.

Finally, prior to 1944 and the deployment of kamikazes the effectiveness of light AA was almost universally poor. This would have been especially true for the IJN for allied pilots were not so inclined to get ever closer to their targets in an effort to ensure a hit. Most ordnance of the day would have been released at the very limit of their effective range, giving them only a second or two of useful defensive fire. After that they became revenge guns. I think a USN skipper summed it up best when he complained about the poor morale the 20mm generated - you simply knew that when they started shooting it was time to run for cover because sailors were about to die.

BTW, in my mod the 25mm is ranked slightly above the 20mm but well below a 40mm. And it only gets ranked higher than a 20mm because there's no simulated shortage of ammo for it. While on paper the 25mm was better than the 20mm, this completely discounts how much harder it was to manufacture the 25mm round. I'm pretty sure there's a report or two (again restricted but later declassed) refering to the shortage of 25mm ammo that existed throughout 1942-45. What the Japanese did to deal with this shortage also tells you that they too knew that the first 1-2 seconds was about the only time you had a reasonable chance of hitting anything with light AA and after that it became nothing more than a revenge gun.

_____________________________

Gary S (USN 1320, 1985-1993)
AOCS 1985, VT10 1985-86, VT86 1986, VS41 1986-87
VS32 1987-90 (NSO/NWTO, deployed w/CV-66, CVN-71)
VS27 1990-91 (NATOPS/Safety)
SFWSLANT 1991-93 (AGM-84 All platforms, S-3 A/B systems)

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Post #: 27
RE: Japanese 40MM? - 11/18/2012 7:44:02 PM   
Natali

 

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quote:

ORIGINAL: sandman455
Analyzing the joules per second of a AA gun? Not sure if that qualifies as ballastics. Novel idea I guess, but it completely negates the imperative issue of having to hit the target. It is after all the MOST important issue. And because of this the true ballistics (as normally defined, check wikipedia) of a gun is the #1 stat in gauging the accuracy and effectiveness of said gun. The higher the velocity, the heavier the round the more likely you will hit the target with an aimed shot. It is supported by every single document I've ever read regarding not only AAA but shooting in general.

You are soooo right. And if this was real life, everything would go arsey-versy. But the game doesn’t calculate like real life so you have to figger out data in game terms and not real life terms. JWE said he paid more attention to the DP and big bore AA guns when he did his AA fix and he just cut a big swag for the auto guns. I am just trying to get the auto guns in line for the update to Babes I am making. Sent my equations to JWE and he likes them, so ….

There is a weird circular calculation in the game about chance to hit and damage by hit. It is almost like calculating damage and if it’s bigger than a threshold, you must have hit. It’s way not that simple, but seems so sometimes; at least that’s what the equations I got say.

Trying to get the data to line up means that everything must be done in exactly the same way. An Effect, that depends on energy delivered per barrel per second is a good start for the game system, even though it is not reality. And you may completely hate my equation for exploding shells and how they figger in, but it is all done to work into the game system.

So people who want to talk about real life this-and-that can do it to their hearts content. But unless they know how it figgers into the game they are just talking about making a pretty OOB, without any thought about how that OOB works in a game way.

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Post #: 28
RE: Japanese 40MM? - 11/18/2012 7:57:14 PM   
PaxMondo


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Gary,

Appreciate your thoughts, but I really disagree.  Your documents are fine, but our interpretations are quite divergent.

Yes, swing and train rates for 5" are not that important.  Range to target is considerably farther, thus vectoring changes are much slower.  25mm swing and train rates would have higher importance as targets are considerably closer, unless all targets are coming in from the same starting position which neither biligerent in this game did.  The concept of multiple vectors was understood by both sides for attack, however the ability to execute these simultaneously was not techinical achievable in the WWII. 

Yes, only a couple of rounds are critical, but to suggest they are the only ones fired is ... let's just agree that a LOT more rounds are fired than those critical 2 by most gunners.  There is plenty of film history (from all billigerents) demonstrating this contrary to AA theory and training.  It takes a lot of combat experience and conditioning to train this reflex out, and not everyone can be so trained. 

Thus during an air attack that might last ~10 min (first to last contact), it would be highly likely that at least one reload would happen.  Probably more.  Slow swap time would mean the gun would not necessarily be in service at a time it could be deployed in defense.  Whether the gunner is replacing the cannister (he didn't) is moot, the gun is OOS. 

So, for modeling purposes, we do have to look at ROF ... not instantaneous ROF, but rather average over a 10 minute engagement.  It is the only way we can account for the fact that some guns will be OOS during that time. OOS might be reload, jam clear, inability to train, whatever.  For modeling, we don't care why, only how much.

Finally, the modern PHALANX system design debunks the concept that ROF doesn't matter ... ROF matters a great deal when TTT (Time To Target) flights are short.  Think of it this way: if I have a high enough ROF, it starts to look like a bat instead of a ball that I am attempting hit my target with.  It is a lot easier to hit a ball with a bat instead of another ball.  WWII systems never got even close to the ROF's of a gattling system in current use, but the theory holds.  And of course, attack speeds then aren't what they are today either ...


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RE: Japanese 40MM? - 11/18/2012 10:37:27 PM   
Natali

 

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So sorry. Thought this was a thread talking about Japanese 40mm T-91s. Didn't know it got turned into wargamers trolling the internet for things to say about gun mounts. I will be more careful in the future.

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