Japanese vs US AA capabilities

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Garyt
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Re: Japanese vs US AA capabilities

Post by Garyt »

..... I'd venture that the real issue with the 25mm was that the IJN was never able to provide better than iron sights for it.
Single mounts had iron sights. The triple mounts used the type 95 fire director. Not sure about the dual mounts, but most were single or triple.

IIRC, the Yamato for instance was orginally equipped with 8 triples, and by wars end it had 40 triples and 30 singles.

The usage of the single weapons may have something to do with the misconceptions as to the range of the weapon. From Navweaps regarding the manual aimed weapons:
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.
alecsandros
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Re: Japanese vs US AA capabilities

Post by alecsandros »

Garyt wrote:
AA Ceiling @ 85 degrees Effective: 9,843 feet (3,000 m) Maximum: 18,040 feet (5,500 m)
... the USN TM to Japan has "AA ceiling less than 1000m", and "fire beyond that that range was completely ineffective".
I read that, however the only thing I see about a 160 RPM rate of fire is this - "The 40mm gun can be operated either fully automatic or single fire. In automatic, it is capable of a maximum cyclic rate of fire of approximately 160 rounds per minute."

That is indeed true, but I see nothing where it retains the 160 ROF at elevation. Check Navweaps - it goes more in depth into the rate of fire issues.
Reports from the Fleet occasionally pointed out that the performance of 40mm guns was sluggish at high angles of elevation. Exhaustive tests proved that with an increase from 0 degrees to 70 degrees the cyclic rate of fire is reduced by approximately 20 rounds per minute. It has been demonstrated, however, that with a wide open setting of the needle valve, a maximum rate of fire at high elevations can be approached.[85]
Note this is a discussion on the types of ammo available for the 40mm. It is stating how long the tracer burns for and how many yards out it burns - which is certainly not the equivalent of the effective range of the weapon. I had mentioned that some rounds self destruct at this range to avoid friendly fire issues. Again, this is not the same as effective range of the weapon.
No,
it is not a question of friendly fire, as the USN ships operated at 1000y from each other during AA formation. The fuze was set in a specific manner to ensure a wall of AA explosions at a particular distance from the firing ship, slightly smaller than the tracking range of the Mk51 directors. The Mark51 would track from 5000y, and the fuze would make the round explode at 4500y - or the range at which the plane would be presuming fire was opened at 5000y [5000y - time of flight for the round. All USN medium and light AA systems were calibrated against 180kts aircraft].
Garyt
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Re: Japanese vs US AA capabilities

Post by Garyt »

.. the USN TM to Japan has "AA ceiling less than 1000m", and "fire beyond that that range was completely ineffective".
Your first quote seems to be very much an incomplete paraphrase. I've directly quoted the two sentences you are pulling from the US technical mission below.

"For the 25mm machine guns at less than 2000 meters range and less than 1000 meters height,a figure of 1500 rounds is quoted.

During interrogations it was stated that beyond the ranges quoted fire was completely ineffective, and that the only result of attempting such fire was to waste ammunition"
Full AA ceiling and Full range with weapons are roughly equivalent. From the above, it looks as though the effective range per the Japanese was abut a total of a little over 2000 meters.

One thing I think we would agree on - there are a fair amount of sources for any of these and other WW2 weapons, and some conflicting information as to ranges, rate of fire, etc.

Judging from a few sources out there, Navweaps and the US technical mission, the effective range of the 25mm seems to be in the 2000-3000 meter range. I would not discount either one of these, but you really need to realize that "effective range" is a very gray area as opinions may vary.

Using the 800-1000 meter range as the effective range for the weapon is sheer fallacy, as this was clearly done to conserve ammo.

The only way I would see an effective range of only 1000 meters is if it were the single barrel manually operated mounts, as I have read a few other places that 1000 meters is about the maximum effective range with any manually operated light AA. The 3 barrel mounts would have a fire control director and powered mount. SO on the late war Yamato, you have 120 barrels in triple mounts, 30 single manual barrels.

I also hope you can see that doctrine plays a roll in range as well. The US believed that fire beyond 1000 meters with a manually aimed weapon was abut useless, but still had their gunners open fire a few hundred meters beyond effective range to sight the weapon in better. A clear departure from Japanese doctrine, largely due to plentiful ammo for the US and no so plentiful for Japan.
Reports from the Fleet occasionally pointed out that the performance of 40mm guns was sluggish at high angles of elevation. Exhaustive tests proved that with an increase from 0 degrees to 70 degrees the cyclic rate of fire is reduced by approximately 20 rounds per minute. It has been demonstrated, however, that with a wide open setting of the needle valve, a maximum rate of fire at high elevations can be approached.[85]
I see a pattern. You find the lowest ROF or range for the 25mm and post it as if it were gospel. You also then post the highest ROF or rnge for the Bofors and post it as if it were gospel. I've certainly found docmentation of a lower ROF for the Bofors than even the 120 RPM due to loading issues. It's Wikepedia, but I've seen this passage many times:
The gun fired a 900 g (2.0 lb) high explosive 40 × 311R (rimmed) shell at 2,960 ft/s (900 m/s).[2] The rate of fire was normally about 120 rounds per minute (2.0 rounds per second), which improved slightly when the barrels were closer to the horizontal as gravity assisted the feeding from the top-mounted magazine. In practice firing rates were closer to 80–100 rpm (1.3–1.7 rounds per second), as the rounds were fed into the breech from four round clips which had to be replaced by hand. The maximum attainable ceiling was 7,200 m (23,600 ft), but the practical maximum was about 3,800 m (12,500 ft).
From the documentation we have, I'd guess the Japanese 25mm had an effective range in the 2000-3000 meter range, the Bofors about 3800 meters. With the US propensity to fire rounds beyond "effective range", this may even be a tad bit overstated. Again, doctrine has much to do when declaring a weapon's effective range. And the Bofors practical rate of fire when used in an AA role was no higher than 120. Even the quote you have about the rate of fire at level at 160 states " a maximum rate of fire at high elevations can be approached."

A maximum rate of fire can be approached. Not equal to, can be approached. Hardly a specific rate of fire mentioned. It does state that maximum cyclical rate is 160, but the maximum cyclical of the 25mm has a maximum cyclical rate up to 260 RPM. The "approaching" of the maximum cyclical rate may well be the mentioned rate of fire of 120. Cyclical is not practical rate of fire.
Garyt
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Re: Japanese vs US AA capabilities

Post by Garyt »

One thing also - look at the muzzle velocity of the 25mm. While it of course is not the only measure of potential range, with similar sized weapons it is indeed of importance. Obviously a larger shell does better as it has less surface area compared to mass, and there are aerodynamic issues with the shells as well, but it is helpful in a comparison.

.50 Caliber - 893 m/s
20mm Oerlikon - 835 m/s
1.1" - 792 m/s
40mm - 881 m/s

25mm - 900 m/s

The .50 caliber has good range for it's size, having similar range to 20mm weapons. Muzzle velocity is one reason why.

The 25mm has a higher muzzle velocity than any of these weapons, though the 40mm with it's larger size and reasonably high muzzle velocity is pretty good as well.
alecsandros
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Re: Japanese vs US AA capabilities

Post by alecsandros »

@Garyt
USN TM to Japan was a very serious project, while navweapona is a site built by enthusiasts, that is growing every day.
When 2 sources are in stark disagreement you should use the primary one.

It seems you avoid the phrases "less then 2000m" and "completely ineffective beyond that range".

Rate of fire for Bofors, as quoted from the document, is of course in reference to the practical expectafions. Thst you do not accept what it is written is another aspect.
The 25mm gun had a practical rate of fire of about 100rpm because of tje very small magazine (15 rounds ? ) - another aspect which should have been improved along with gun sights...
For comparisons you should study the German 20mmflak and the USN 1.1" in terms of effective range . The 25mm will fit about in the middle between them.
Steve Crandell
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Re: Japanese vs US AA capabilities

Post by Steve Crandell »

I was at one time a Tank crew member. We had a 30 cal coax and a 50 cal gun for the TC. Both have about the same muzzle velocity, but I can tell you the ballistics aren't even close. Obviously muzzle velocity is important, but there are a number of other factors. One of the important things when shooting at aircraft is the range at which you don't have to allow very much for shell drop. It is very hard to tell when shooting a gun at a fast moving aircraft whether the rounds are going high or low.
Garyt
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Re: Japanese vs US AA capabilities

Post by Garyt »

Obviously muzzle velocity is important, but there are a number of other factors.
Of course, which is why I prefaced what I said regarding muzzle velocity with this -
While it of course is not the only measure of potential range, with similar sized weapons it is indeed of importance. Obviously a larger shell does better as it has less surface area compared to mass, and there are aerodynamic issues with the shells as well, but it is helpful in a comparison.
If you were in an M60 tank, you probably had the .50 BMG with a muzzle velocity in the 880-920 range depending upon ammo. Your .30, of the 7.62 NATO round would be in the 830-790 range. You have the worst of both worlds with the .30, smaller round and lower muzzle velocity.

I was not saying the Japanese 28mm outranged the Bofors 40mm - but it should outrange the 1.1", and should have overall good range characteristics for it's size.

But muzzle velocity is indeed very important. Look at the British 40mm "Pom-Pom" weapon, deemd about 1/2 as effective against conventional attack vs the Bofors by the British. It had about the same sized shell as the Bofors, it's ROF was a bit worse, in the 96-115 range. It's reall issue - Muzzle velocity. 585-701 meters per second depending on ammo used to the Bofors at 881 meters per second. Huge difference, the Pom-Pom was more of an early interwar design, at least as used as AA for a naval vessel. It could handle slower moving aircraft of the late 20's better than aircraft of WW2.
Garyt
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Re: Japanese vs US AA capabilities

Post by Garyt »

USN TM to Japan was a very serious project, while navweapons is a site built by enthusiasts, that is growing every day.
When 2 sources are in stark disagreement you should use the primary one.
First of all, the 2 sources are not in "stark disagreement". They way you are twisting the statements of the technical mission may be in stark disagreement with the Navweaps info.

Secondly, I'm surprised you are disparaging the work on the NavWeaps site. I consider Nathan Okun as one example more than just "an enthusiast", and the Navweaps info in generally very well researched. Indeed the USN tech mission to Japan was a serious project - but look at the passages in there you are hanging your hat on.

It is based on interviews with defeated Japanese officers. These are opinions, not quantified results. educated opinions yes - but opinions. And really, we are not going to get truly quantified numbers from anyone. Even testing of the weapons as not going to be the same as trying to shoot down moving aircraft in a combat enviroment.

Navweaps is a very research intensive site. Where they came up with the numbers I do not know, I may ask. But I would not just blow off their research as you have done.
It seems you avoid the phrases "less then 2000m" and "completely ineffective beyond that range".
Do not avoid them at all. First of all, this is opinion as I have stated above. Secondly, "completely ineffective beyond that range" would imply effective within that range would it not? Less than 2000 meters distance, 1000 meters elevation. Per Pythagoras about 2200 meters. Maximum effective range judging from what they are saying.
Rate of fire for Bofors, as quoted from the document, is of course in reference to the practical expectafions. Thst you do not accept what it is written is another aspect.
This is almost amusing. You have one document, and it's NOT your highly touted US technical mission to Japan. Tis one site, the hyperwar site that you believe supports your higher rate of fire for the Bofors than listed anywhere else. This then must be right, and every other bit of info wrong, because it supports your opinion I assume.

And the funniest thing about it is that it does not specifically state your 160 rate of fire. I mention how the how the maximum rate of fire "may be approached". Again, not quantify. And again, it does not say "may be equaled". So what does approaching a cyclical rate of 160 mean? 120? And you fail to give any credence about the comment regarding the manual reloading procedures lowering the rate of fire to somewhat less than even the 120rpm.

I can perhaps see where you would want to rely on the technical mission to Japan. Again, it's opinions of interviewed Japanese when discussing the effective range of the 25mm, but I see why you may like this source. However, when it comes to the various info on the Bofors, you pick one site (Hyperwar) which is clearly an enthusiast site (which is how you discredit Navweaps) and view it as having the only accurate info on the Bofors.

This is hardly a sound principle for research. Pick only the sites that concur with your opinion, even twist them a bit, and ignore any shred of contradictory evidence. That's research done only to try to prove your opinion correct, not open minded minded research to find the truth.



Have a few questions for you, alecsandros.
1) What is your definition of "effective range"?

2) In your opinion, how do you quantify this? Asking for specifics here.

3) Do you think the fact that Japanese withheld fire until allied planes were within 1000 meters at a a later stage of the war had something to do with conservation of ammo?
alecsandros
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Re: Japanese vs US AA capabilities

Post by alecsandros »

Garyt wrote:
Have a few questions for you, alecsandros.
1) What is your definition of "effective range"?

2) In your opinion, how do you quantify this? Asking for specifics here.

3) Do you think the fact that Japanese withheld fire until allied planes were within 1000 meters at a a later stage of the war had something to do with conservation of ammo?
1) It is the range at which the guns were considered to be effective by their operators
2) Through empirical research.
3) Yes.

I have a few questions for you as well:
1) "defeated Japanese officers" in 1946 know less about their own weapons then the posters from Navweapons in 2015 ?
2) What do you understand from
"The 40mm gun can be operated either fully automatic or single fire. In automatic, it is capable of a maximum cyclic rate of fire of approximately 160 rounds per minute. A unique characteristic of this gun is that the trigger mechanism controls the rammer operation only; once the ramming cycle is started, the round is loaded and automatically fired without further control."
[...]
"Exhaustive tests proved that with an increase from 0 degrees to 70 degrees the cyclic rate of fire is reduced by approximately 20 rounds per minute"
[...]
"that with a wide open setting of the needle valve, a maximum rate of fire at high elevations can be approached.[85]
[/i]
Mostlyharmless
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Re: Japanese vs US AA capabilities

Post by Mostlyharmless »

As I knew nothing about this topic, I have been using Google to try to find something to say. I still know very little but I have begun to suspect that the effective range of light AA was as much determined by the gun sights as by the gun's ballistics and rate of fire. There is of course a trade off in that a predictive gun sight has less work to do if the time of flight is reduced.

One of the source found was a discussion here a few years ago viewtopic.php?f=36&t=897&start=45 from which I can quote dunmunro giving the RN view:

The "Maximum Effective Ranges" of close range weapons are as follows:-
2-pdr. multiple Pom-Pom and Bofors in local control 1,700 yards.
Oerlikon 20 mm. single gun 1,000 yards.
0.5 in. Machine gun. 800 yards.
0.303 in. and 0.30 in. weapons 400 yards.
http://hnsa.org/doc/br224/part4.htm#par473 (paragraph 470 for above data)

An interesting unofficial USN view from Robert Wallace, who trained many USN gunners, can be found at http://ibiblio.org/hyperwar/USN/rep/DamnNeck/index.html including some interesting points.

For example, his view of the 1.1 inch was not wholly positive:

“...while the 1.1-inch proved to be a disappointment in many ways. A number of critics have mentioned the frequent premature explosions of the excessively sensitive shells within the gun barrel itself. Commander Gallery commented that they would "go off when fired into heavy rain." Our "prematures," like those at Dam Neck, tended to explode just abaft the flash shield, to the great discomfiture of both crew and bystanders. Unlike at Dam Neck, however, we were lucky that nobody ever got hurt in the process. Even if satisfactory ammunition had been developed, our 1.1-inch required the nearly full-time service of a gunner's mate first-class to keep it firing with a minimum of jams.”

He mentions that the Oerlikon and the 40 mm Bofors were much more reliable and explains the advantage of self-destructing shells:

“To anyone who has ever had the terrifying and helpless experience of being in an anchorage during a night or twilight air attack (real or imagined), in company with a lot of auxiliaries whose nervous 20mm gunners needed only a shot or two to cause panic, the 40mm Bofors had another advantage. The old saying "What goes up must come down," while unfortunately true of the Oerlikon, did not apply to the Bofors. Once the tracer element burned out at 4,000 to 5,000 yards, the ammunition self-destructed.”

His estimate of effective range was on the low side, i.e. “In practice, range setting was less important than it might seem, particularly within the ranges at which the 20s and 40s could be expected to have their main effectiveness, say inside 600-800 yards for the 20mm and 1000-1500 yards for the 40mm. The reason was that out to these ranges the trajectories were relatively flat.”

However, the best part may be his discussion of gun sights. Wallace was an advocate of using the gyro sight rather than using tracers to aim (tracers were still useful to distract enemy pilots).

“As a lifelong wing-shot, I became enamored of the Mark 14 sight and was soon an advocate. The sight needed an advocate at that point in the war because it tended to have a bad reputation among many old hands. Older gunner's mates would sometimes tell trainees to look around the sight and direct the tracers like a stream of water. This method was known as tracer control. What its advocates did not realize was that the human eye, with limited inter-pupillary space, could judge distance only to about 400 yards, beyond which all is optical illusion. As soon as I began firing it myself, the reason for the problem became clear. Firing-line instructors were gunner's mates. They felt their job was to teach the guns and to put the students through the firing line. The guns were not the problem. The students simply were firing before they were ready. I soon had students dry-tracking and learning to handle the reticle before actually firing. And just to show that the Mark 14 was not as bad as they might have heard, I often fired demonstration runs myself in those early months, sometimes on the 20mm and sometimes on the 40mm. I well recall an experience that indicated something of the nature of the problem. With Larry Springer setting range, I announced that we would fire three runs with a 40mm twin. However, when we shot the sleeves down on the first two runs and the flyer was stringing another sleeve, our chief came to me and said, "Mr. Wallace, I wish you and Mr. Springer wouldn't shoot anymore. We have to get these men to lunch."

This matches Yoshida Mitsuru comments from “Requiem for the Battleship Yamato”, pages 75-6:

“The muzzle velocity of a 25 mm machine-gun bullet is less than 1,000 meters per second, barely five or six times the average speed of the American planes.
Using tracers to correct the aim of weapons at such a speed disadvantage is like chasing after butterflies with our bare hands.”

Thus the 25 mm Type 96 was a reliable gun with high velocity but with its rof limited by a small magazine. Changing barrels was also much slower than for the Oerlikon, which may have made a large magazine less attractive. However, the Type 96's real problem was that the single mount had only iron sights whilst the Type 95 short range H.A. director, which normally controlled three triple mounts, received the comment “It is curious that the Japanese Navy took no steps at all to design any other form of sight based on more advanced principles or which were tachymetric” in the USN Technical Mission to Japan Report O-30, page 54, http://www.fischer-tropsch.org/primary_ ... 200-30.pdf. By “more advanced”, they may have meant something containing gyroscopes, which was an area where Japan was behind the USA.

Finally, note that the IJN may have been asking their 25 mm guns to do a job that even the Bofors could not have managed. When the IJN chose the 25 mm in preference to the Oerlikon, the main aerial threat to battleships were torpedoes dropped by biplanes less advanced than the Swordfish at about 90 knots. During the dispute in the 1930s between Yamamoto Isoroku and Takahashi Sankichi advocating air power and battleship admirals such as Nakamura Ryozo, Koga Mineichi, the leader of the General Staff section in charge of equipment, stated that battleships could defend themselves. He may have meant that such a slow biplane forced to fly a constant course for up to 20 seconds to set the torpedo's gyro could be hit.

Unfortunately for Yamato in April 1945, torpedoes had improved. By 1944, the recommended dropping speeds and heights for USN torpedoes were 260 knots and 800 ft. This gives a flight distance of about 1000 yards and thus the torpedo is dropped at a range of 1,400 yards to allow it to arm https://www.youtube.com/watch?v=R552QfbD8AU. The time to set the gyro was reduced to 10-12 seconds, so that the aircraft was flying a predictable course from just beyond 3,000 yards to 1,400 yards.

Of course, IJN torpedoes had also improved. Even in 1941, IJN torpedoes had been able to be dropped at higher speeds than other nations torpedoes (note Adm. Phillips insistence as the first attack on Prince of Wales developed that the IJN aircraft were flying too fast to drop torpedoes) and the 45 cm Type 91 Mod 3 from 1943-4 http://www.navweaps.com/Weapons/WTJAP_WWII.htm could more or less match the torpedoes described in the USN video. However, the USN had the 5”/38 with the proximity fuze.

Interestingly, the last battleship to be completed, Jean Bart, had 57 mm “light” AA and Germany had a prototype 55 mm working by 1945 http://www.navweaps.com/Weapons/WNGER_55_Gerat58.htm, which could get shells to 3,000 metres in about 4.34 seconds.
Garyt
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Re: Japanese vs US AA capabilities

Post by Garyt »

Thank you for jumping in. mostly harmless. You input is helpful and interesting. It's nice to have someone else posting instead of Alecsandros and I beating up on each other :D
I think one of the biggest problems is "effective range" cannot and or is not defined in a quantifiable manner. We even have a number of terms relating to it - "Maximum effective range", "effective range", etc. etc.

Interesting about the 1.1" - there seem to be some problems with it not relating to the obvious such as range, ROF, magazine size, etc.

Interesting also about the 25mm. It seems as though the practical ROF of 110 might be it's practical maximum even with a better feeding system - unless a quick barrel change or even better a water cooling system was used.

To really "beef up" the 25mm you would need a cooling system, a better fire director and perhaps more substantial (massive) mounts. This would make it a pretty effective weapon that could throw a decent sized shell with high velocity and a great rate of fire - But it would also make it a lot heavier and of course be lacking in range compared to something like the Bofors.
1) It is the range at which the guns were considered to be effective by their operators
2) Through empirical research.
3) Yes.
1) Well, this puts a lot of faith in them and again is still not quantitatively defined unfortunately.
2) LOL, I asked for a specific answer and this is about as vague as possible :D
3) At least there is one thing we agree on
1) "defeated Japanese officers" in 1946 know less about their own weapons then the posters from Navweapons in 2015 ?
It's not "posters" from Navweaps, it's those that write the articles. But to answer your question - very possibly so. Ask any US fighter pilot what the best US fighter craft of WW2 was, and they will tell you theirs, unless perhaps they were unfortunate enough to be in a Brewster the entire war. I think sometimes asking the end user gets bad information because they cannot see "the forest for the trees. And these "posters" as you say are researchers, they glean their info from a good amount of research.

I'll ask you something - who knows better as to how many inches of belt armor the Yamato's shells can penetrate at what range - one of those in the gun crew, or Nathan Okun? Please let me know your answer.
2) What do you understand from
Well, I understand that everything you are quoting from that article is referencing CYCLICAL rate of fire, not practical rate of fire. Heck, in that case the Japanese 25mm has a ROF of about 240. Please look:
it is capable of a maximum cyclic rate of fire of approximately 160 rounds per minute. A unique characteristic of this gun is that the trigger mechanism controls the rammer operation only; once the ramming cycle is started, the round is loaded and automatically fired without further control."
[...]"Exhaustive tests proved that with an increase from 0 degrees to 70 degrees the cyclic rate of fire is reduced by approximately 20 rounds per minute"
Speaking of cyclical rate of fire as opposed to practical rate of fire is like comparing apples to walnuts.
alecsandros
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Re: Japanese vs US AA capabilities

Post by alecsandros »

... @MostlyHarmless, GaryT,
I am surprised as to the banality with which you treat official USN documents. :think:
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