The PERFECT WAR Mod : Guns

[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. [8D]

[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?

[JWE]

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.

[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".

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.

[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. 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

[FatR]

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).

[JWE]

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. [8D]

[JuanG]

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%?).

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.

[FatR]

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.

[JuanG]

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.

[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

[JuanG]

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.

[oldman45]

Just when it gets interesting and you two take it to PMs.........[8|] so unfair! [:)]

[JWE]

ORIGINAL: oldman45
Just when it gets interesting and you two take it to PMs.........[8|] 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. [8D][8D]

[oldman45]

There are certain people I will follow their threads so I know what ya mean.

[JWE]

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.

[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

[JuanG]

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...

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.

[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.

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.

[JuanG]

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.

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.