Japanese vs US AA capabilities

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aurora
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Re: Japanese vs US AA capabilities

Postby aurora » Sun Dec 21, 2014 10:15 am

The Naval Historical Center essay notes that growing the responsibility of the nascent CIC organization necessarily upset the old order of doing, who was reporting to whom, and most of all, of communications protocols where now CICs within a task group were, when possible, joined in permanent communication links to even the lowliest destroyer escort or fleet auxiliary, adding the eyes and reports of their lookouts to those of similar watch-standers about the fleet as a whole.

In short the CICs continually grew for a time, superseding old organizational structure and supplanting them with a new system filtering and shaping information to a newly empowered command group. The tasks and facilities put at the service of the CICs also grew within a ship. While in 1943 a destroyer CIC might just have been configured for anti-ship and anti-submarine warfare tasks, by the Battle of the Philippine Sea when set out as radar pickets had to undertake forward air controller (FAC) functions and somehow jam in air search radar and anti-air action control functions.

From that beginning, were added the corporate experiences of the continuing series of naval air and naval surface actions around and about the Battle of Guadalcanal in the Solomon Islands campaign. By late 1943 when the first new construction carriers of the Essex-class fleet carriers and the Independence-class light carriers with many associated fleet vessels had reinforced the refitted USS Enterprise (CV-6) and the USS Saratoga (CV-3), the U.S. Navy was prepared to take the offensive and began evolving CIC procedures and operational doctrine for a fleet of carriers.
Quo Fata Vocant-Whither the Fates call

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Garyt
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Re: Japanese vs US AA capabilities

Postby Garyt » Mon Dec 29, 2014 11:57 pm

42/43 stats RPB 42/43 RPM Birds per minute
5” 42352/96 441 19 .043
5”VT 9128/61 150 19 .127
40mm 120465/ 1451 120 .083
1.1” 67,858 1616 100 .062
20mm 853,558/ 4225 285 .067
.50 cal 447,995/47 9531 450 .047
.30 cal 77461/2 38731 450 .012

Above is a table I made using the report listed here- http://www.history.navy.mil/library/onl ... y_wwii.htm - which is a Navy report on the effectiveness of US AA fire.

I used 43/43 for a few reasons, 44/45 was a different setting that took into account the ability to kill a kamikaze, which to me should be treated a bit differently than standard AA fire.

There are a few issues here that might skew the results a bit, biggest one would be opening fire beyond the effective range of the weapon, though that should to some extent even itself out. Light (40mm and lighter) AA is somewhat easy to compare directly, the Heavy AA is a bit different.

But with the final stat of birds per minute of fire, it's pretty easy to compare light A weapons. The only thing lacking is seconds under fire, where the range of the weapon is taken into account. But one word of caution here - A 20mm has an AA ceiling of about 3000 meters- the 40mm about 6500 meters. This does not mean the 40mm is going to have twice the "time under fire", or doubling it's birds per minute compared to a 20mm. The biggest issue is that it seems most light AA declined dramatically in effectiveness after 1000 meters. Even with something like the 400mm Bofors, I'd guess after 1500 or so meters it's accuracy declines.

It's also rather difficult to compare ranges on weapon as some have an "effective" range listed, others do not. An effective range by nature is a gray judgement term anyway. A "formula" would be possibly something along the lines of using the weapons max range, and then somewhere around 750 or so meters halving everything above that, and again halving anything over 1500 meters to determine "time of fire" on the target.

For comparison sake, form the US Technical mission to Japan in 1946 " The Type 96 was most effective when used at ranges of 1,000 meters or less. Japanese military estimated that it required an average of 1,500 rounds to down an aircraft at a height of 1,000 meters and a range of 2,000 meters and that fire beyond that range was completely ineffective. Later in the war when ammunition supply was restricted, firing was held until the targets were within 800 meters range this dropped to a low as seven rounds per aircraft according to Japanese sources".

This puts the weapon somewhere between the US 1.1" and the 40mm Bofors, so it seems as though it fits right in with US light AA for it's caliber, though I would not think the kill ratio for the Japanese 25mm was quite as well documented based upon the precise statistics the US navy had access to.

But to really compare light AA to light AA - take the birds per minute x average time on target (A function of the weapons range) and I think we would have a pretty good idea of the effectiveness of the various weapons.

A few of my biggest surprises - the 40mm Bofors seems better than other weapons, but not head and shoulders above. And the US .50 caliber is not as bad as I thought it would be. The US 1.1", though not a Bofors still would have perhaps 1/2 of the effectiveness of the Bofors, depending upon the ranging characteristics I has mentioned.

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Re: Japanese vs US AA capabilities

Postby Garyt » Mon Dec 29, 2014 11:58 pm

I might add the table dd not post like I was hoping it would.

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Re: Japanese vs US AA capabilities

Postby Steve Crandell » Tue Dec 30, 2014 12:46 am

How in the world do you assign kills to 20mm, when 5" and 40mm have been shooting at the same target before the 20mm even begins firing?

How do you assign kills to 40mm when the target may have already been damaged by 5" fire? Does the 5" only get credit when it downs a target before anything else begins firing?

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Re: Japanese vs US AA capabilities

Postby Garyt » Tue Dec 30, 2014 1:11 am

How in the world do you assign kills to 20mm, when 5" and 40mm have been shooting at the same target before the 20mm even begins firing?

How do you assign kills to 40mm when the target may have already been damaged by 5" fire? Does the 5" only get credit when it downs a target before anything else begins firing?


Well, for exact details on the "scorekeeping" you would probably have to ask the Navy.

As far as a 40mm goes, it's contact fused. So unless it hits the aircraft, it's not going to detonate. So no detonation of a 40mm shell = no kill. And a 40mm is generally going to be able to knock a strike type aircraft out of the sky.

EDIT: I would also mention that I see "half kills" in the stats on the various weapons, so there must have been some method of sharing a kill in the case that both weapons caused damage.

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Re: Japanese vs US AA capabilities

Postby Garyt » Sat Jan 03, 2015 2:44 am

You know, after looking at these statistics and calculating things like range and time on target, I'm rather surprised.

I'd like to add a few other things:

From Navweaps:

Effective range during World War II against aircraft for manually aimed weapons rarely exceeded 1,000 yards (910 m), although USN Oerlikon gunners were expected to open fire at 1,200 or 1,300 yards (1,100 or 1,200 m) which allowed aiming corrections by the point the target entered effective range.


This would apply to the .30 and .50 caliber weapons, the 20mm Oerlikon (Most Oerlikon montings were a single weapon), and the single mountings of the Japanese 25mm (usually roughly 1/4 of the 25mm barrels on a IJN Vessel)

Interestingly enough, the US 20mm when used in dual mounts was considered about as effective as 1.5 singles - same with the Japanese 25mm, which the three barrel mounts were considered about as effective as two singles. The 25mm was considered to suffer from excessive vibration, but only the 3 barrel configuration, the single barrel configuration did not suffer from this.

Another problem shared by both the US 28mm quad mount and the Japanese 25mm triple mount - excessive vibration. This is often listed as a problem with the 25mm, but the US weapon had the same issue. Makes sense when you look at the weapons - both had a relatively light "mount" weight compared to pounds of projectiles fired when compared to say the 40mm Bofors.

Per Ranges, it looks as though the 20mm and lighter guns had a max effective range of maybe 910 meters, as they were manual. The Japanese weapon seemed to be more in the 1800 Maximum effective range, though this would seem to apply only to the powered triple mounts, and I'm not sure how many of these mounts were powered. I'd guess the 28mm US weapon to be somewhere around here as well.

The 40mm would of course have the best range, though I'm not sure where it would fall. It's max ceiling is about 8000 meters, compared to 5500 for the Japanese 25mm (I used the Japanese records of the captured 40mm's for max ceiling as they shold be "speaking the same language" as Japanese ascertations of their own 25mm max AA ceiling)

The things that seemed to go against my common beliefs -

1) The US .50 Caliber. It has apparently a better range than the 20mm that replaced it, I would think mostly to do with the aerodynamics of the projectiles. It seems though that both would have an effective range in the 910 meter range as both were hand operated. The 20mm seems only to be about 1.5 times as effective therefore as the .50 caliber - which seems to go against the US airforces thoughts, that a 20mm was 3 times as effective as a .50 caliber in air to air. I'm really not sure what to think here, but it seems as though from a weight perspective, you are better off with .50 calibers than 20mm's. One gun and 5 minutes of ammo puts you at 320kg or so with the .50 caliber, but at about 1000kg with the Oerlikon 20mm. I guess deck space is a consideration as well, but I really don't see the advantages based on kills to replace the .50 caliber with 20mm guns, unless something is off. Maybe the .50 caliber was more effective in the Pacific Theatre because it was used against planes without self sealing fuel tanks or armor.

2) The much maligned 25mm Japanese Weapon - When you look at the combination of it's kill ratio and range, it seems to be a pretty good weapon. Add this to the fact that it did not have a lot of topside weight per barrel, which was about 1000kg, similar to the US 20mm for barrel and 5 minutes of ammo, it seems to come out rather well. It outranged the US 20mm by a good amount, and was a lot lighter than the 40mm in terms of topside weight. My guess is that the Japanese figures could be somewhat wrong, I'd feel much more comfortable if these kills per round were confirmed by US losses, OR if it was from the same source that conformed US AA kills, which is of course impossible. Still though it seems to be a decent light AA weapon compared to the other light AA available, it just does not compare favorably to the 40mm Bofors. And I might add that it got it's "kill numbers" vs durable US planes, not against Japanese fireballs without self sealing fuel tanks.

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Re: Japanese vs US AA capabilities

Postby Steve Crandell » Sat Jan 03, 2015 4:47 am

You are apparently using "kills per round fired", which is extremely misleading. There is absolutely universal belief that the 20mm is FAR superior to the .50mg in both shipborne AA and air-to-air applications.

I think those statistics are also incorrect, because there was a lot of over reporting. I think I mentioned this before. An aircraft goes down. It was fired at in succession by 5", 40mm, 20mm, and .50 cal and it doesn't actually crash until the .50 cal shoots at it, but it has been on fire since shortly after the 5" opened fire. ALL weapon crews claim it, including every 20mm and .50 cal weapon on the ship. Let's say 50 crews claim the shoot down. Are you now going to claim 50 kills? How do you know which one shot it down?

The stats are impossible to get right. I can't imagine any way to make them very meaningful.

Here is another aspect of this which figures into the 5" results. USN ships with 5" guns were encouraged to shoot at absolutely every aircraft they might have a chance to hit. This means that if there are a few aircraft attacking a TF, every 5" weapon in the TF that can bear on the target is going to open fire, even though most of them really don't have much of a chance of hitting the target because of their location and what the target is doing. Statistically, every one of those rounds fired is going to be tabulated to determine "rounds per kill" for the 5" gun, and that is a completely inaccurate way to determine the weapon's actual performance.

Suppose instead you had some magical means to determine which 5" gun actually destroyed an aircraft. It fired 7 rounds, for 7 rounds per kill. The rest of the 5" guns on the ship and the TF fired 500 rounds at the target. We have 507 rounds per kill.

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Re: Japanese vs US AA capabilities

Postby Garyt » Sat Jan 03, 2015 5:16 am

. This means that if there are a few aircraft attacking a TF, every 5" weapon in the TF that can bear on the target is going to open fire, even though most of them really don't have much of a chance of hitting the target because of their location and what the target is doing. Statistically, every one of those rounds fired is going to be tabulated to determine "rounds per kill" for the 5" gun, and that is a completely inaccurate way to determine the weapon's actual performance.


Which is why I left out 44 and 45. In 44 and 45 you had an overabundance of flak. In 45 you had many attacks by a small amount of aircraft AND an overabundance of Flak. Plus techniques to get very close before being detected, and attacks that don't represent conventional attack - kamikazes.

I think those statistics are also incorrect, because there was a lot of over reporting. I think I mentioned this before. An aircraft goes down. It was fired at in succession by 5", 40mm, 20mm, and .50 cal and it doesn't actually crash until the .50 cal shoots at it, but it has been on fire since shortly after the 5" opened fire. ALL weapon crews claim it, including every 20mm and .50 cal weapon on the ship. Let's say 50 crews claim the shoot down. Are you now going to claim 50 kills? How do you know which one shot it down?


To a point what you are saying is correct. BUT ALL weapons on the vessel have the same chance to get credited for too many kills.

US kills were not too far from Japanese planes lost, at least in the earlier battles such as Santa Cruz. IIRC the claims from AA and CAP were about double the Japanese losses. If it was as "overclaimed" as what you write suggests, we should multiply Japanese losses by 50 fold to equal American claimed kills.

I know it not 100% accurate - but it should be somewhat accurate in comparisons from gun to gun. The red herring are the kills claimed by the 25mm, as these are likely judged by another yardstick.

But I do indeed think something is wrong with the .50 caliber to 20mm claims, though it's not as simple as "overclaiming" I don't think, unless only the .50 cal's were doing the overclaiming. I'm trying to figure out why the discrepancy. I might add that the ratio of 28mm to 40mm kills seems fairly accurate. The 40mm is going to have more time on target, making it a bit better than 2x effective as the 40mm.

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Re: Japanese vs US AA capabilities

Postby Byron Angel » Sat Jan 03, 2015 1:13 pm

Over-claiming (or "multiple-claiming") is a known feature of such relatively chaotic engagement environments. But ex post facto analyses of large numbers of such actions, where claimed kills can be retrospectively compared to actual losses as tallied by the opponent, can usefully quantify the differential between claimed and actual results. Perfect analytical precision may indeed be impossible to achieve, but I do believe that such studies are nevertheless ultimately valuable.

B

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Re: Japanese vs US AA capabilities

Postby Garyt » Sat Jan 03, 2015 6:08 pm

Absolutely Byron. The exact numbers may not be there, but it should give you a general idea.

As I said, the one thing that I question is the relative effectiveness of the .50 cal compared to the 20mm, I'm wondering why. A few ideas:

1) To small of a sample base for the .50 cal? A lot of rounds were fired, but it is based on a sample base of 47 kills in the first two years of the war, 38 of these being in 1942. The 20mm results are based on 202 kills.
2) Perhaps the 20mm would open up fire at longer ranges than their effective range, while the .50 caliber would hold their fire til closer ranges?

I'm really not sure here what the reason is, but I do think the 20mm should be more effective than the rounds per kill show. Or the .50 caliber should be less effective.

The other one is the 25mm - I think the "overkill" numbers here are more inflated than they are for the American weapons. It would seem this should be the case, though I'm also guessing the 25mm may not be as bad of an AA weapon that it is given "credit" for. Actually, it's numbers are similar to the US 28mm, whcih has a similar range, rate of fire and projectile weight, so the kill numbers may actually be accurate.

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Re: Japanese vs US AA capabilities

Postby Steve Crandell » Sat Jan 03, 2015 7:31 pm

For more info on the IJN 25mm I suggest the following link: http://navweaps.com/Weapons/WNJAP_25mm-60_mg.htm

There are good references on that site for most naval weapons.

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Re: Japanese vs US AA capabilities

Postby Garyt » Sat Jan 03, 2015 8:14 pm

Thanks Steve, that's where I get most of my info on naval weaponry.

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Re: Japanese vs US AA capabilities

Postby Steve Crandell » Sat Jan 03, 2015 9:28 pm

Garyt wrote:Thanks Steve, that's where I get most of my info on naval weaponry.


OK, but note the mention there of the small magazine size, etc. Your rounds per kill don't mean as much if you aren't able to fire very many rounds.

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Re: Japanese vs US AA capabilities

Postby Mostlyharmless » Sun Jan 04, 2015 4:07 pm

Garyt wrote:...snip...
Really the only Japanese light AA weapon of the war was the much maligned 25mm/60. Strictly as a gun only, it seemed to be fine. It had a good muzzle velocity and a maximum rate of fire in the 240 range. Unforunately there were other problems. It's loading system lowered it's effective rate of fire to 110rpm - a belt fed or feeding system similar to the 40mm bofors would have helped. ...snip...

The big difference between the 1.1 inch and the 25 mm Type 96 is that the 1.1 inch was water cooled but the Type 96 was air “cooled”. The 15 round magazine allows the barrel to cool while the magazine is being changed. If the IJN had wanted something like Bofor's system allowing continuous reloading, they would have had to add water cooling and the weight per barrel would have approached that of the 1.1 inch.

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Re: Japanese vs US AA capabilities

Postby Garyt » Sun Jan 04, 2015 8:15 pm

OK, but note the mention there of the small magazine size, etc. Your rounds per kill don't mean as much if you aren't able to fire very many rounds.


Yeah, I'm fully aware of that. Takes the rate from a cyclic of about 240 to a 115 or so practical. Compares fine to the US 1.1" with an effective of 100 (150 Cyclic), and even the Bofors 40mm with an effective of 120.

It just does not have the range or the punch of the 40mm, or in many cases it does not have the power traverse and elevation of the 40mm. Which has a few redeeming qualities as manual can traverse or elevate even if power is knocked out on a temporary or permanent basis, but it comes at a loss of traverse and elevation speed generally unless in a single mount.

It's cyclic ROF of 240 is very good compared to other weapons of similar caliber - a better method of loading would have made a huge difference, either a hopper style like the Bofors or possibly belt fed.

The big difference between the 1.1 inch and the 25 mm Type 96 is that the 1.1 inch was water cooled but the Type 96 was air “cooled”. The 15 round magazine allows the barrel to cool while the magazine is being changed. If the IJN had wanted something like Bofor's system allowing continuous reloading, they would have had to add water cooling and the weight per barrel would have approached that of the 1.1 inc


Where the 1.1" falls short is even with it's water cooling and added weight, it still does not quite match the effective ROF of the 25mm.

The 25mm certainly had it's shortcomings, and I'm not going to say it was on par with the 40mm Bofors. But it was not a bad weapon, and with a few changes (loading method, power mounts for all with sufficient traverse elevation spedd, sighting) it could have been an excellent weapon. I'd put it a step ahead of the US 1.1". Possibly better or on even terms with the 20mm Oerlikon, but it's tough to compare as the Oerlikon falls in the camp of smaller short range light AA, the 25mm is more mid range light AA. It's max AA ceiling of 5500 meters puts in more in line with the 1.1" and 40mm than the 20mm with it's 3050 max AA ceiling.


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