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The PERFECT WAR Mod : Guns - 8/18/2011 7:08:51 PM   
JWE

 

Posts: 6580
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Status: offline 		Didn't think it right to step on the main thread for this, so opened another for gunbunnys everywhere. Lest I be accused of being a fanboi for one side or t'other, here's the US 6"/47 shooting the Mk-35 and 8"/55 shooting the Mk-19 and Mk-21 plotted (blue) over the corresponding Japanese guns.

The 6 inch gun specs are wicked close. US 8 inch gun specs are significantly better. Read shell steel for them. For 6 inchers, it gets down to RoF, and dispersion. The US guns had 4x the former and 1/2 the latter. Even at the end of the war, Japan could never come close to even the Mk-4 of the 1936 Brooklyns, in any way, shape, or form. Sigh ... what a sad day for JFBs. Japanese gun technology sucked so bad (when viewed realistically) it might be worthwhile forgetting about it.

Ciao.




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< Message edited by JWE -- 8/18/2011 7:09:58 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 7:32:49 PM   
oldman45


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Status: offline 		My understanding was they used a process called wire wound in making their barrels and that caused a lot of problems. Was it something else?

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 8:37:53 PM   
JWE

 

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quote:

ORIGINAL: oldman45
My understanding was they used a process called wire wound in making their barrels and that caused a lot of problems. Was it something else?

Not really. Wire winding was cool, so was monoblock, so was lined, on either base. Technology to make a good gun barrel was decades well understood. There's a lot of hard humping wire wound barrels (particularly in the larger calibers) still shooting today. Land Systems, in South Africa, is banding their barrels, with longitudinally stressed composit steel bands.

The witch was floating and fretted liners.

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 8:39:06 PM   
JuanG


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Status: offline 		While I agree that the Japanese had several issues to overcome, I dont feel this was one of them.

John paints a surprisingly one sided picture. I'd be very interested in your sources for blanket statements like "4x ROF and 1/2 dispersion".

Heres what I've got on the subject.



Dashed lines are deck penetration vs US Class B, solid ones belt penetration vs US Class A.

The blue lines are the US 6"/47 firing the Mk35 Mod1-8 130lbs shell at 2500fps.

The green line is the same gun with the Mk35 Mod9-11, which was introduced in 1944 and like other US latewar shells enjoyed superior metalwork. This shell did not appreciably change the deck penetration capabilities of the weapon.

The red lines are the IJN's 6.1"/60 firing the Type 91, 123.2lbs @ 3020fps. While a lighter shell, the insane muzzle velocity of this weapon gave it armour penetration capability almost on par with 8" weapons.

The long and short of this is; no contemporary shell design will overcome a 20% difference in MV. Now of course, the Japanese paid for that MV as they did with most of their weapons with a shorter barrel life, about 25-30% of that of the US gun, but thats a trade off they had to make to get the performance they wanted.

Regarding rates of fire; the IJN 6.1"/60 turrets had shell hoists at 6rpm and powerhoists at 5rpm; which was the maximum sustained rate. The US 6"/47 had shells at ~8rpm (Brooklyn class) or ~10rpm (Cleveland class). While this is noticably higher (60-100%) than the IJN mount, one has to remember that the US is using semi-fixed ammo vs the IJNs shell+bags. It is likely that a semi-fixed IJN mount could have achieved perhaps 7 or 8 rpm.

Regarding dispersion; the IJN 6.1"/60 had a dispersion of ~1.4% of range past 15kyds just before the war. I do not have any dispersion data for the US weapon, but given that the Iowa 16"/50s had a dispersion of ~0.65% of range when they were reactivated and updated in 1980, I'm a little bit skeptical about the claim of the 6"/47 having the same sort of performance. Certainly unlikely if one goes by the US heavy cruisers track records. Another issue entirely in fire control in general, but even here the US was not that far ahead at the beginning of the war, though US ships did benefit from RPC whereas Japanese ones did not, which helped improve accuracy through the elimination of operator error, an important consideration for tired crews at sea.

I'll do another post on CA's later, as things are more interesting and even there...

John; please could make it clear what is what on your graph? I had some trouble figuring out what was what, and thats considering I knew roughly what to look for. Thanks.

< Message edited by JuanG -- 8/18/2011 8:58:26 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 9:32:17 PM   
JWE

 

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Status: offline 		OMG, another gunbunny!! Juan, I love you like a brother!! Towards thee I roll, thou all-destroying but unconquering Spaniard; to the last I grapple with thee. You make my life fun, mi amigo. Bring it, Bro. Gosh, I love your posts.

No, I only plotted the early war stuff, because that's where John and Stan were going. I used Nathan Oakuns program, because I used it for Babes and because it gives consistent numbers.

I can't understand where you would get a US 6" gun penetrating 8" of armor, or a Japanese 6" gun penetrating 10" ??? Bad, bad, bad, if we are talking from differented bases. Would you please provide a source for this !!!

As to the 4x value, it's simple, it's differential RoF reported by NavWeaps. 10 vs 5 is 2x. As to dispersion, in 1941, the reported Japanese dispersion value for her 8" gun was 360 meters. According to the USN gunnery tables from 1939, the dispersion of the 8"/55 was 200m at 20kyds. I don't know at what range the 360m Japanese dispersion was measured at, but 200 vs 360 is pretty close to 1:2. Ok, it's 0.5555 ... so sue me.

From hell's heart, I shall never stab at thee.

Ciao. John


< Message edited by JWE -- 8/18/2011 9:45:13 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 9:33:36 PM   
FatR

 

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quote:

ORIGINAL: JuanG

While I agree that the Japanese had several issues to overcome, I dont feel this was one of them.

John paints a surprisingly one sided picture. I'd be very interested in your sources for blanket statements like "4x ROF and 1/2 dispersion".

4xROF is completely unbelievable. It will require 20/minute ROF. Actual practical ROF was more like 8 (with 10 as theoretical maximum probably). I've taken 8-10 from navweaps as well, and I haven't seen "20" there. As about dispersion, what are actual figures for 6in/47?

Going on a tanget a bit, the result of actual fighting do not confirm superiority of US weapons. The only naval battle which might be considered as an US victory in a gunnery duel against a superior force is First Guadalcanal. And even then, even after a quite lucky hit, Hiei would have limped away, turning it into an IJN "victory by points", had Japanese been able to provide sufficient aircover for her. The Battle off Samar might be considered a serious failure of Japanese gunnery, but I'm not knowledgeable enough to say what role the need to avoid air attacks played there. Cape Esperance, Second Guadalcanal and Empress Augusta Bay all featured significantly heavier Allied forces, never mind Surigao Strait. In smaller-scale ambushes on Tokyo expresses (Battle off Horaniu, Cape St.George) US forces similarly always had numerical advantage and/or ships of a heavier weight category (an APD converted from ten- to twenty-years long DD isn't exactly a match for a Fletcher one-on-one), never mind a tactical advantage of not having tasks other than seeking the enemy.

So, I look at supposed awesomeness of US cannons and don't see it reflecting in actual combat results. The only area where Japanese seem inferior is their desroyer gunfire, which hardly ever hit anything during various Tokyo Express battles, and even then, it should be considered that a noticeable part of destroyers running the Express just didn't have many (or modern) guns, and that the decisive American victories stated above were achieved by torpedo ambushes. IJN's armament system had enough real flaws to count inability to produce victory in surface combat against superior forces more than half the time as one).

Juan, thanks for producing some actual numbers, instead of mere deliberations).



< Message edited by FatR -- 8/18/2011 9:39:52 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 9:40:46 PM   
JWE

 

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quote:

ORIGINAL: FatR
4xROF is completely unbelievable. It will require 20/minute ROF. Actual practical ROF was more like 8 (with 10 as theoretical maximum probably). John, this does not look like an impartial assessment. I've taken 8-10 from navweaps as well, and I haven't seen "20" there. As about dispersion, what are actual figures for 6in/47?

Whoops. Yes, 2x not 4x. A Senior moment.

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 9:54:24 PM   
JuanG


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quote:

ORIGINAL: JWE

I can't understand where you would get a US 6" gun penetrating 8" of armor, or a Japanese 6" gun penetrating 10" ??? Bad, bad, bad, if we are talking from differented bases. Would you please provide a source for this !!!

As to the 4x value, it's simple, it's differential RoF reported by NavWeaps. 20 vs 5 is 4x. As to dispersion, in 1941, the reported Japanese dispersion value for her 8" gun was 360 meters. According to the USN gunnery tables from 1939, the dispersion of the 8"/55 was 200m at 20kyds. I don't know at what range the 360m Japanese dispersion was measured at, but 200 vs 360 is pretty close to 1:2. Ok, it's 0.5555 ... so sue me.

Ciao. John



I'm also using Okuns Data, run though NaAB, with NavWeaps as the main source for MV, RoF and weight parameters.

No idea where you got 20 rpm from on NavWeaps. 6"/47 lists 8-10rpm, and even 6"/47DP only hits 12 rpm. 20rpm is comparable to the 5"/38. EDIT: Ah, no worries then. Glad were on the same page.

Note that the penetration data I posted does NOT correct for the effects of caliber/thickness ratio increase, etc which tends to flatten it out at the lower end. This is simply because the data was calculated as hypothetical maximum penetration as a comparison tool.

In 1936 Nachi class was getting 300-360 yards dispersion at 22-24kyds. This was improved by some 10-15% by 1941, which would give us 270-325yds or so. The 6.1"/60 is in the same category, as the increase in MV correlates with the increads barrel length, both around 20% (this is important because as a rule short barrel + high velocity = dispersion -> see Nelsons 16"/45, incase anyone in interested). If the US tables say 200m, then thats 220yds or so (~1.1%).

I have a little trouble believing that figure for the Mk9 guns which werent all that accurate; which is why the Mk12 from CA-37 onwards reduced MV by 100fps. It is possibly that this figure is for those guns, in which case it is believable. The same gun with the 335lbs projectile would have had slightly better performance yet.

The 6"/47 is interesting as altough the MV is lower, so is the barrel length. I would guess that it would most likely be a little worse off than the US 8"/55, so maybe 250-275yds at 20k (~1.25%?).


quote:

ORIGINAL: FatR

The Battle off Samar might be considered a serious failure of Japanese gunnery, but I'm not knowledgeable enough to say what role the need to avoid air attacks played there.



I think Samar serves to illustrate the importance of the "niceties" the US ships had compared to the IJN, with regards to fire control. RPC and radar FC are both things that can work to counter human error; case in point, Samar. After suffering air attack and probably being at battlestations all night out of fear/hope of crashing into a US task force, I have no doubt that the IJN sailors were both exhausted and nervous. Couple this with the fact that they suffered from air harrassment during the action and I can very easily see a series of compounding human errors leading to rather erratic shooting. One salvo might be a straddle, the next off several hundred yards, as the guy adjusting the elevation reads his pointer wrong and adjusts incorrectly. Do this for all 3 turrets and youve got a confused fire director who now has no idea what went wrong, and has to start from scratch more or less. RPC was nice because it did all (most of) this for you. This is just my own theory on why the IJN botched their shooting that day, but I think its reasonable enough.


< Message edited by JuanG -- 8/18/2011 10:13:42 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 10:18:26 PM   
FatR

 

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quote:

ORIGINAL: JWE

OMG, another gunbunny!! Juan, I love you like a brother!! Towards thee I roll, thou all-destroying but unconquering Spaniard; to the last I grapple with thee. You make my life fun, mi amigo. Bring it, Bro. Gosh, I love your posts.

No, I only plotted the early war stuff, because that's where John and Stan were going. I used Nathan Oakuns program, because I used it for Babes and because it gives consistent numbers.

I can't understand where you would get a US 6" gun penetrating 8" of armor, or a Japanese 6" gun penetrating 10" ??? Bad, bad, bad, if we are talking from differented bases. Would you please provide a source for this !!!

As to the 4x value, it's simple, it's differential RoF reported by NavWeaps. 20 vs 5 is 4x. As to dispersion, in 1941, the reported Japanese dispersion value for her 8" gun was 360 meters. According to the USN gunnery tables from 1939, the dispersion of the 8"/55 was 200m at 20kyds. I don't know at what range the 360m Japanese dispersion was measured at, but 200 vs 360 is pretty close to 1:2. Ok, it's 0.5555 ... so sue me.

The last pre-war numbers provided by Lacroix/Wells put mean dispersion of 203mm guns as 380m at 20km, 330 at approximately 20k yards. (155/60 by comparison had around 280m dispersion at 20km.) In theory US gun is much superior. In the practical test of long-range gunnery at Komadorski Islands, Salt Lake City fired 832 8in shells and hit nothing (all five hits on Nachi were by 5in shells), while Maya and Nachi fired 1613 203mm shells, achieving 9 hits. (Data for Jap cruisers is from Lacroix/Wells, for Salt Lake City I got lazy and consulted Wikipedia). So, while one actual engagement doesn't provide enough data for a definite conclusion, it makes me seriously doubt assertions about inferior accuracy of Japanese cruiser guns (127 3YT's on destroyers are another matter - you might have noticed that I don't like this gun at all...). Maybe the key to success was in other element of the gunnery system, of course, but then the guns themselves at least weren't inadequate enough to undermine it.




< Message edited by FatR -- 8/18/2011 10:19:39 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 10:38:59 PM   
JuanG


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Status: offline 		And, as promised, the 8" weapons;

Same deal, dashed is deck vs Class B, solid is belt vs Class A.

First lets have a look at the whole set.



Okay, thats a mess; lets do this in sets of 3 weapons. First up, the US Mk9 and Mk12 with the Mk19 260lbs shells.



The light blue is the US 8"/55 Mk9 firing the Mk19 Mod4-6 260lbs shell at 2800fps.

The dark blue is the US 8"/55 Mk12 firing the same shell at 2700fps.

The pink line is the IJN 8"/50 3YT-II firing the Type 91 277.4lbs shell at 2756fps.

And next the late war guns.



The light green is the US 8"/55 Mk12 firing the Mk21 Mod1-4 335lbs shell at 2500fps.

The dark green is the same gun firing the Mk21 Mod5 335lbs shell at 2500fps. This was introduced in 1944. No real change to deck penetration.

The pink is the IJN 8"/50 3YT-II firing the Type 91 277.4lbs shell at 2756fps (same as above).

Again, the IJN weapon is a solid contender, especially compared to the prewar guns, and is a noticably better deck penetrator than the light US shell. Compared to the heavier 335lbs shell, it maintains an edge up close, but looses out medium-long range, and against deck armour.

Back to dispersion; that 360 meter/yard figure seems to be suffering from unit ambiguity it seems. Regardless, I think its not unreasonable to conclude that yes, although the IJN 8" did have more dispersion than comparable US guns (though I still claim the Mk9 with 260lbs shell was just as bad), the difference was not noticeable and no doubt occluded by other factors.

< Message edited by JuanG -- 8/18/2011 11:46:18 PM >

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 11:41:54 PM   
JWE

 

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Status: offline 		Yep, as I said elsewhere, it's not 20 it's 10. OK.

But your curves are from Mars, dude. Where in the world do they come from? I'm using FACEHARD, and I would be pleased to pm you with the input parameters. It's important to speak from the same bandstand.

Ciao. J

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RE: The PERFECT WAR Mod : Guns - 8/18/2011 11:54:40 PM   
JuanG


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quote:

ORIGINAL: JWE

Yep, as I said elsewhere, it's not 20 it's 10. OK.

But your curves are from Mars, dude. Where in the world do they come from? I'm using FACEHARD, and I would be pleased to pm you with the input parameters. It's important to speak from the same bandstand.

Ciao. J


Feel free. I can also pass you the paramaters I'm using in NAaB for these. Maybe better to take this to PMs as you say since we seem to be drifting into specifics.

< Message edited by JuanG -- 8/19/2011 12:05:26 AM >

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 4:34:05 AM   
oldman45


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Status: offline 		Just when it gets interesting and you two take it to PMs......... so unfair!

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 2:37:39 PM   
JWE

 

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quote:

ORIGINAL: oldman45
Just when it gets interesting and you two take it to PMs......... so unfair!

Oh, we'll be back. Rest assured. We're just ironing out the nitty gritty differences between the programs and the input variables; make sure we understand which hymnbook we're each singing from.

Besides, it's too much fun discussing this stuff with someone like Juan to ever pass the chance by.

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 3:55:33 PM   
oldman45


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RE: The PERFECT WAR Mod : Guns - 8/19/2011 6:32:17 PM   
JWE

 

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Status: offline 		Ok, enuf with the pm’s. I’m not ignoring anybody, just getting tight with Juan. Am astonished, and quite pleased at the number of people who actually run Nathan Oakun’s program. Am impressed. For ya’ll, here’s my nitty gritty. Juan’s is a skoosh different, because his program is different, so no worries, this is just my side. So for them of you who can play with the math:

Use FACEHARD, v 6.8. It’s DOS and a bitch to input and resolve, but works for me, who is an old legacy fart anyway. Heck, I can still use a slide rule and know what a logarithm is. Some inputs are:

8”/55, AP Mk-19/1, 260lb shell, 216lb body, muzzle velocity 2800 fps
8”/55, AP Mk-19/4, 260lb shell, 203lb body, muzzle velocity 2800 fps
8”/55, AP Mk-21/4, 335lb shell, 268lb body, muzzle velocity 2500 fps
6”/47, AP Mk-35/1, 130lb shell, 107lb body, muzzle velocity 2500 fps
6”/47, AP Mk-35/9, 130lb shell, 100lb body, muzzle velocity 2500 fps

203/50, AP 91-T, 277lb shell, 263lb body, muzzle velocity 2750 fps
155/60, AP 91-T, 123lb shell, 117lb body, muzzle velocity 3015 fps

For the ballistics program that calculates striking angle and velocity, ogive crh and bourelette are directly from OP 1664 (TM 60A-2-1-11/12). Assumed best case (same) values for Japanese shells (everybody’s equal in my eye). Ballistics coefficient (BC) is assumed 1 to begin, and curves normalized to reported data, to extract effective BC, then re-ran with ‘e’BC. All atmospherics are standard, and best case; 750 mm HG, 15° C, no cross perturbations, and ignored altitude atmospheric density differential for everybody.

Made best case assumptions for obliquity. 90° target aspect, no yaw or tumbling; straight forward strike angle.

Used the ‘Effective’ naval ballistic limit; where things penetrate with the body and fuse in condition to operate. There are many other penetration limits that look at different penetration parameters. My personal choice is EBL, and I use that for all results (my consistency metric).

Am trying to figure out how to do my strike angle/strike velocity tables for these guns so they look nice. Might just have to dump the wretched beasties as an excel file in a zip.

Am doing a massive data dump for Juan. Got his NaAB program and am running my stuff with it. We should (hopefully) get some congress on this stuff.


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RE: The PERFECT WAR Mod : Guns - 8/19/2011 6:51:34 PM   
Big B

 

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Status: offline 		Juan and JWE, I am happy to read you guys are pouring into this stuff.

One point in getting accurate gun data on penetration to keep in mind when using Nathan Okun's stuff (he has printed tables for all of his data) -
For Allied guns use indexes vs Japanese armor & vice versa - for Japanese guns use indexes vs American armor.

You do get substantially different results than when using US to US, & Jpn to Jpn figures....


B

< Message edited by Big B -- 8/19/2011 6:52:16 PM >

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 7:01:04 PM   
JuanG


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Status: offline 		Looking forward to it. Sorting through my own data and putting it into a better format to share/post.

Out of curiousity I tried to find if NAaB or FCHD68 came up with different results given the same imputs, but the results are identical.

Example, IJN 6.1"/60 at pointblank.


So I'm not sure where we seem to be falling out of sync. One thing you said caught my attention though; you said your data was all at best case strike angle; I hope this does not mean you are disregarding angle of fall?

Also, excel is fine. It is the program of kings...


quote:

ORIGINAL: Big B

Juan and JWE, I am happy to read you guys are pouring into this stuff.

One point in getting accurate gun data on penetration to keep in mind when using Nathan Okun's stuff (he has printed tables for all of his data) -
For Allied guns use indexes vs Japanese armor & vice versa - for Japanese guns use indexes vs American armor.

You do get substantially different results than when using US to US, & Jpn to Jpn figures....


B


I run everything versus the same target armour, in this case US Class A. Otherwise no comparison can be made. I suppose a second set vs something else like KC or JVH could be done, but Im pretty sure the same trend continues.

The effects of armour quality and slope is not something thats modelled in AE, though I have done my best to adjust armour to account for these in AltWNT Mk2.

< Message edited by JuanG -- 8/19/2011 7:03:26 PM >

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 7:07:24 PM   
Big B

 

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Status: offline 		Yes - but the different armor types are exactly what needs to be taken into account - because US guns are not used against US armor and vice versa....except of course during friendly fire.
quote:

ORIGINAL: JuanG


I run everything versus the same target armour, in this case US Class A. Otherwise no comparison can be made. I suppose a second set vs something else like KC or JVH could be done, but Im pretty sure the same trend continues.

The effects of armour quality and slope is not something thats modelled in AE, though I have done my best to adjust armour to account for these in AltWNT Mk2.



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RE: The PERFECT WAR Mod : Guns - 8/19/2011 7:31:00 PM   
JuanG


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quote:

ORIGINAL: Big B

Yes - but the different armor types are exactly what needs to be taken into account - because US guns are not used against US armor and vice versa....except of course during friendly fire.
quote:

ORIGINAL: JuanG


I run everything versus the same target armour, in this case US Class A. Otherwise no comparison can be made. I suppose a second set vs something else like KC or JVH could be done, but Im pretty sure the same trend continues.

The effects of armour quality and slope is not something thats modelled in AE, though I have done my best to adjust armour to account for these in AltWNT Mk2.




If I was doing this to calculate penetration values to work out values to use for a device, then yes, I agree.

However, as I am doing this to prove that Japanese weapons were not as inherently inferior as claimed in the first post, then the standard against which they are tested needs to remain constant regardless of the weapon in order to reach a workable conclusion.

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 8:29:07 PM   
JWE

 

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quote:

ORIGINAL: JuanG
So I'm not sure where we seem to be falling out of sync. One thing you said caught my attention though; you said your data was all at best case strike angle; I hope this does not mean you are disregarding angle of fall?

No, Sir. Strike angle is the angle at which a shell will impact a target, along a ballistic trajectory. Angle of fall, all that stuff. Only using vertical obliquity, no yaw, no twist, no tumble, just simple orthogonal ballistics trig.

For the raw ballistics, I use Interleave Systems v104. Math is the same as Nathan's, so just normalize to reported values. All that's of interest is striking angle and striking velocity, anyway. And it's all normalized.

< Message edited by JWE -- 8/19/2011 8:37:56 PM >

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 8:40:09 PM   
JuanG


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quote:

ORIGINAL: JWE


quote:

ORIGINAL: JuanG
So I'm not sure where we seem to be falling out of sync. One thing you said caught my attention though; you said your data was all at best case strike angle; I hope this does not mean you are disregarding angle of fall?

No, Sir. Strike angle is the angle at which a shell will impact a target, along a ballistic trajectory. Angle of fall, all that stuff. Only using vertical obliquity, no yaw, no twist, no tumble, just simple orthogonal ballistics trig.


Figured it would be something like that, so I apologise for even asking. Was just grasping at straws hoping to find where things go wrong. Right now I can only assume were working to entirely different calculated limits for the weapons, but even that should only shift our results in one direction or the other; we seem to be getting different trends entirely for some of them.



quote:

ORIGINAL: JWE

For the raw ballistics, I use Interleave Systems v104. Math is the same as Nathan's, so just normalize to reported values. All that's of interest is striking angle and striking velocity, anyway. And it's all normalized.



I use NAaBs ballistics model which is based on Robert McCoys work, backed up by BigGun from Rick Robinson (particularly for non-historic weapons), and check this all against secondary data where possible. Generally NAaBs model is within 1-2% of secondary data, and can be corrected where needed. Would be interested in hearing more about this program you use as I've never come across it, despite scouring the internet for ballistics programs.


< Message edited by JuanG -- 8/20/2011 6:13:21 AM >

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RE: The PERFECT WAR Mod : Guns - 8/19/2011 10:36:12 PM   
FatR

 

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Status: offline 		I just want to say that I'm wathching the discussion with interest... Thanks, Juan and John.

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RE: The PERFECT WAR Mod : Guns - 8/20/2011 6:28:12 PM   
JWE

 

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Status: offline 		Hi Juan, Interleave isn't a specific ballistics program, it's a full boogie math analysis program. Costs a butt load, but we have a small-site license, so I can play with it.

Input the complete (as I can get them) ballistics equations, including all the drag and dynamic motion crap. Then set everything I could rationally justify to '1':
No vertical displacement - gun and target on same plane
No horizontal deflection - target axis is 90 degrees to gun azimuth
.. no pitch motion; gun and target are stationary
.. no track motion; gun orthogonal and target axis are parallel
Standard meteorology - Nav OP standard conditions
.. ignored altitude function of atmospheric density
.. no wind
Standard trajectory of shell axis - tangent to calculated trajectory
.. no yaw, pitch, skew (might give +/- 5 degrees to SA), assumes direct tangent
Standard ballistics coefficient
.. nominal except 'form factor' (i) which is extracted from G5 body type and normalized to 1
.. bourelette diameter set to nominal shell diameter

That pretty much seems to be the booger. So ran it and plotted the results against the published range tables in Nav-OP 1237, 830, 807, 243, et seq. Did a curve fit with K' as the fitting parameter, and went for a four point fit, at 0k, 10k, 20k, 30k yds, and lo and behold, with a K' of 1.31, I get a curve match with a maximum of 1.3% offset for any calculated data point. And that ain't bad. Especially considering the Navy used an emperical K' in constructing the tables anyway. Because they couldn't do the complex atmospheric math either, so they went empirical and extracted a K' value. Go figure. Woof !!

Sending you the data tables: Actual OP-Nav numbers compared to calculated JPr numbers from 0 to 26k-32k, in 2k increments. Giving the K' numbers, the bourelette diameters, ogive diameters, crh calcs, shell and body weights, and bears, oh my!

Ciao. John

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RE: The PERFECT WAR Mod : Guns - 8/21/2011 4:16:24 AM   
PaxMondo


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quote:

ORIGINAL: JWE

Hi Juan, Interleave isn't a specific ballistics program, it's a full boogie math analysis program. Costs a butt load, but we have a small-site license, so I can play with it.


Now, that's what I call a nice perk.



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RE: The PERFECT WAR Mod : Guns - 8/21/2011 6:05:43 AM   
el cid again

 

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There are advantages and disadvantages to different national technologies. If you pick your argument carefully - well - one might come to
quite different conclusions.

While I am not quite a JFB - my Navy chief was right when he alleged "Japan had better warships." That wasn't entirely a matter of gunnery,
nor the technical specs of the guns - but there are cases where it was.

There is universal consensus, internationally, that the best Japanese gun was the 10 cm (3.9 inch 65) Type 98. Used on AA destroyers and in more than 110 mountings ashore, it was a superb weapon, for which there is nothing comparable in the US at all. It is a fine weapon in terms of ballistic performance - weight of shell - ROF - range - etc. But much more - also in terms of rate of elevation and traverse of the mountings, and in terms of the fire control system - which was almost unique in Japan. But there is still more - Japanese naval AAA was supported ashore by what, today, we would call "simulator" training - for which we had no comparison. While the Japanese did not permit AA gunners to fire live ammunition - they had much less need to do that than we did - since they could train in the simulators. These used actual directors, actual fire control computers, and scale models of target aircraft "flying" on wires - inside something like a planetarioum which could simulate all lighting conditions. So - wether one takes the weapon purely as a gun - or as a weapon system - it was absolutely fine. The AA destroyers - with four twin mountings - were able to outrange and put more weight of metal on a traditional destroyer - and in simulation, at least - you don't want to have to face one.

There is a lesser case, far less well known. This weapon is actually related, designed at the same time, as a pure AA mounting - and it is comparable really only to a post war US 3 inch 50 - the kind I served with 20 years later - better than similar sounding wartime and pre-war 3 inch 50s. But the Japanese had it operational during the war. This is the 76 mm (3 inch 60) Type 98. It used the same fire control system as the 4 inch described above. It was, however, not widely made - serving in a light cruiser class and in four twin mountings ashore at Maizuru. But IF the Japanese had produced it instead of older 3 inch guns - it would have changed the game. It replaces the need for medium AAA - not just is superb heavy AAA.

Other cases of superior Japanese guns exist. The Japanese had a late war 5 inch comparable to a US 5 inch 54 - except the US model - I served with it as well - NEVER was successful. But the Japanese perfected the weapon in 1945 - not a bad achievement in the conditions.

On land, the IJN fielded something almost wholly unknown. Japanese naval 8 inch guns were adapted into single mountings for AAA use - so were 6 inch - and the 8 inch was wholly unknown for 60 years - except insofar as it was the basis for orders that B-29s not attack Singapore (we were not entirely sure what the weapons was?). The battery was found a few years ago - in a park - covered with foliage. Remarkably, the mountings look for all the world like the 155 mounting intended for modern US destroyers and, sometimes, for support ships - a very sleek, streamlined - and light weight - mounting. There was also an Army 149.1 mm weapon fielded only to defend the Imperial Palace - but it was only of marginal performance - particularly in elevation and traverse. The 8 inch - as the 5 inch - and the 4 and 3 inch described above - wes without peer - in that era. Only decades later did the French field a somewhat similar 100 mm - we never have done - and as I noted - our post war 3 inch 50 was at least in the same league. But for 1938 designs? Remarkable work.

So - "forget the whole thing" is complely unfair and misleading.


quote:

ORIGINAL: JWE

Didn't think it right to step on the main thread for this, so opened another for gunbunnys everywhere. Lest I be accused of being a fanboi for one side or t'other, here's the US 6"/47 shooting the Mk-35 and 8"/55 shooting the Mk-19 and Mk-21 plotted (blue) over the corresponding Japanese guns.

The 6 inch gun specs are wicked close. US 8 inch gun specs are significantly better. Read shell steel for them. For 6 inchers, it gets down to RoF, and dispersion. The US guns had 4x the former and 1/2 the latter. Even at the end of the war, Japan could never come close to even the Mk-4 of the 1936 Brooklyns, in any way, shape, or form. Sigh ... what a sad day for JFBs. Japanese gun technology sucked so bad (when viewed realistically) it might be worthwhile forgetting about it.

Ciao.





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RE: The PERFECT WAR Mod : Guns - 8/21/2011 3:11:53 PM   
JuanG


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quote:

ORIGINAL: JWE

Hi Juan, Interleave isn't a specific ballistics program, it's a full boogie math analysis program. Costs a butt load, but we have a small-site license, so I can play with it.



Handy. Probably would have had access to something similar at University, but unfortunately that opportunity is gone.

Regardless, I think its clear that theres some differences were getting on our ballistic data, as well as possibly using a different standard to measure against.

I propose we both post the ballistic data for the IJN 6.1"/60 and the US 6"/47 and see where our results differ, and compare them to the real figures.

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RE: The PERFECT WAR Mod : Guns - 8/21/2011 8:06:06 PM   
JWE

 

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Joined: 7/19/2005
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quote:

ORIGINAL: JuanG
Regardless, I think its clear that theres some differences were getting on our ballistic data, as well as possibly using a different standard to measure against.

Think so, too. Might have found at least one source of discontinuity. Ran NaAB and found few significant differences in the 6", Mk-36, between NaAB model and mine/Nathans. Striking angle/velocity were all ok. My form factor was a skoosk different, but when I tweaked the NaAB model with a (slightly) different ballistics coefficient, it came in, perfect, for angle and velocity as a function of range/elevation. Pen still bit the Willy, so wtfo?

Then, the light dawned. NaAB uses the standard Mk-36, Mod 1-?, with 106.9 lb body wt. It shows the parameters, but one can't modify them. Hope to gosh that I was specific enough, somewhere, to say I was plotting the Mk-35, Mod 9, with 100.2 lb body wt. This dude penetrates better then the earlier shell. The earlier shell penetration numbers agree reasonably well between FACEHARD and NaAB, but NaAB can only run its standard shell set. One cannot tweak shell parameters in NaAB ... sigh ...
[am furiously adding the nominal and the differences to the the data set. Think I see just where we agree, and where/why we do not]
quote:

I propose we both post the ballistic data for the IJN 6.1"/60 and the US 6"/47 and see where our results differ, and compare them to the real figures.

Yeah, let's definitely do that. I haven't had this much fun since I ran into the Le Petomaine thruway and had to go back home to get a $hitload of dimes (Mel Brooks joke). Seriously, let's do that.

Ciao. John

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RE: The PERFECT WAR Mod : Guns - 8/21/2011 9:00:05 PM   
JuanG


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quote:

ORIGINAL: JWE


quote:

ORIGINAL: JuanG
Regardless, I think its clear that theres some differences were getting on our ballistic data, as well as possibly using a different standard to measure against.

Think so, too. Might have found at least one source of discontinuity. Ran NaAB and found few significant differences in the 6", Mk-36, between NaAB model and mine/Nathans. Striking angle/velocity were all ok. My form factor was a skoosk different, but when I tweaked the NaAB model with a (slightly) different ballistics coefficient, it came in, perfect, for angle and velocity as a function of range/elevation. Pen still bit the Willy, so wtfo?

Then, the light dawned. NaAB uses the standard Mk-36, Mod 1-?, with 106.9 lb body wt. It shows the parameters, but one can't modify them. Hope to gosh that I was specific enough, somewhere, to say I was plotting the Mk-35, Mod 9, with 100.2 lb body wt. This dude penetrates better then the earlier shell. The earlier shell penetration numbers agree reasonably well between FACEHARD and NaAB, but NaAB can only run its standard shell set. One cannot tweak shell parameters in NaAB ... sigh ...
[am furiously adding the nominal and the differences to the the data set. Think I see just where we agree, and where/why we do not]


The Mod9 thru Mod11 with 100.2lbs body, introduced in 1944 is available in NAaB too, 3 lines below the earlier Mod1 thru Mod8 shell used for the early years. Slightly misguiding as the line starts with 3", but its right there. I plotted it on my first curve too.

I get exactly the same numbers out of NAaB as I do out of facehard for that shell.

Will get you a table of 6.1" ballistics at 5.5kyds intervals, and a 6" table at 6k, 10k, 16k, etc later tonight.

< Message edited by JuanG -- 8/21/2011 9:05:44 PM >

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RE: The PERFECT WAR Mod : Guns - 8/21/2011 10:02:01 PM   
JWE

 

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Status: offline 		You are a Prince, Juan. Thank you.

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