Iowa Class real performance

[Bgile]

Something to add:
The German 15" shell performance, good or bad, was proven in BB vs. BB combat as was the German armour. We know how it really works due to factual evidence as that from Bismarck´s mission.
We don´t have that factual evidence from the Iowas because they never engaged in BB vs BB combat, we only have test evidence that is not the same as real post action forensics.
On paper the 16"/50 MkVII is a faster and more powerfull gun-shell combination than 15"/47 of Bismarck. But I don´t believe that an Iowa would shoot the German ship and win easily, if wining at all is the climax of such combat.

The US shells performed quite well against Kirishima and Jean Bart. The very same shells, just lower muzzle velocity.

[Tiornu]

"The German 15" shell performance, good or bad, was proven in BB vs. BB combat as was the German armour. We know how it really works due to factual evidence as that from Bismarck´s mission."

What was the 15in shell proven to do? Defeat limited thickness of HT steel? And what was German armor proven to do? Fail when struck by large shells? How is this proof of any quality.

"We don´t have that factual evidence from the Iowas because they never engaged in BB vs BB combat, we only have test evidence that is not the same as real post action forensics."

No, we also have evidence from battle. SoDak took a direct hit on her barbette armor at short range from a 14in shell. Not only did the shell fail to penetrate, but the turret remained in action.

[Karl Heidenreich]

Tiornu:

What was the 15in shell proven to do? Defeat limited thickness of HT steel? And what was German armor proven to do? Fail when struck by large shells? How is this proof of any quality.

No, we also have evidence from battle. SoDak took a direct hit on her barbette armor at short range from a 14in shell. Not only did the shell fail to penetrate, but the turret remained in action.

The Bismarck armour didn´t failed so miserably. The amidship hit by PoW hit below the armoured belt, so the shell didn´t went thru the armour at all. And that hit proved to be unsusbtancial.

About the So Dak hits I must agree that it´s evidence... of Japanese 14" against So Dak. No 15" L/47 hits.
Anyway, as I said before: the Iowa stands a better chance, but I will not underestimate the Bismarck. Last felow who did it blew with her ship.

[marcelo_malara]

No, we also have evidence from battle. SoDak took a direct hit on her barbette armor at short range from a 14in shell. Not only did the shell fail to penetrate, but the turret remained in action.

The 14" was an HE shell, not AP.

[Dave Saxton]

The faceplate angle was a plus. It presented a sharp angle to low trajectory high velocity (close range) hits, and only got closer to "normal" impact angle at long ranges where the shells were much less likely to retain enough velocity to penetrate.

Tests were apparently (source: Nathan Okun) performed postwar which showed the British 14" was unable to penetrate the Iowa class faceplates at any range. The shells deformed and ricocheted. In general, it was apparently unlikely for a shell to penetrat any armor thicker than the shell's diameter.

It's a simple matter of physics that the US 16"/50 cal gun was more powerful than the German 15"/47. There is a large difference in muzzle energy, and there is anecdotal evidence that the US Shell performed better at the target.

Once again I see equating the penetrating power of the KVG 14" with the German 15"/48.5. The 15"/48.5 is much closer to the 16"/50, than the 14"/45 is to the 15"/48.5 in penetrative power.

It would be nice if all that need be done is make sure that the armour is thicker than a potential attacking shell, but it doesn't work that way in most cases. An AP shell could penetrate armour of greater effective thickness than it's diameter. At long range the German 15" has enough terminal velocity to penetrate the Iowa face plate at the likely striking angle.

Of course the larger 16"/50 is more powerful. That's not in question. What is in question is to what extent. As it turns out, the difference in penetrative power is marginal, not great.

Which AP shell has the more powerful bursting charge?

[Tiornu]

The 14" was an HE shell, not AP.

Incorrect. It was an AP shell.

[marcelo_malara]

Sorry Tiornu, are you speaking about the Guadalcanal night battle where the Japanese had their guns loaded with HE because they were going the shell Henderson? I didn´t know they managed to load AP.

[Tiornu]

You're right that there's a lot of confusion about the ammo the Japanese were using. The key shell was the Type 3, which was neither AP nor HE, but a hollow shell filled with incendiary capsules, virtually useless against ships. The night of Nov 13, San Francisco got hit by a dozen 14in shells--fortunately for her, all were Type 3's. On the night of Nov 15, when engaging SoDak, Kirishima managed to fire Type 3's and some Type 0 HE shells and some Type 91 AP shells. The hit on SoDak occurred while Kirishima was firing AP only. The fragmentation damage on SoDak is also consistent with an AP hit.

[marcelo_malara]

In what angle did the shell strike?

[Bgile]

Once again I see equating the penetrating power of the KVG 14" with the German 15"/48.5. The 15"/48.5 is much closer to the 16"/50, than the 14"/45 is to the 15"/48.5 in penetrative power.

You completely missed the point. It wouldn't penetrate at MUZZLE VELOCITY, which is much more energy than Bismarck's 15" at 20k yds. We have no reason to believe Bismarck's shells would perform better.

It would be nice if all that need be done is make sure that the armour is thicker than a potential attacking shell, but it doesn't work that way in most cases.

How are you going to cover your citadel with 18" of armor? Leave out the guns and the engines? In most cases, it DOES work that way, but there is no way to include armor that thick except in limited areas.

An AP shell could penetrate armour of greater effective thickness than it's diameter. At long range the German 15" has enough terminal velocity to penetrate the Iowa face plate at the likely striking angle.

First, it can't because of the effects above. Secondly, show me the numbers to back up your assertion. The facehard equation shows partial penetration of 17.6" at 22K. Is that the "long range" you refer to? And that doesn't take into effect the 30 deg angle of the US Turret face. As the range gets less, the impact angle gets greater, unlike hits on the German armor. The US 16" can penetrate 14.4" of German face hardened armor at 28K. Isn't that an advantage?

Of course the larger 16"/50 is more powerful. That's not in question. What is in question is to what extent. As it turns out, the difference in penetrative power is marginal, not great.

I don't dispute that except for deck armor penetration, which is much greater for the 16" gun. My point is that the heavier gun will penetrate Bismarck's turrets at longer range than the reverse because bismarck has much thinner armor on the turret faces, and the German armor is vertical.

Which AP shell has the more powerful bursting charge?

Bismarck's does. 41.4 lb vs 40.5 lb. The difference is so small as to be insignificant, except that the much heavier body of the 16" shell (800 lb heavier) imparts a lot more kinectic energy to whatever it hits and is more likely to penetrate instead of breaking up. That is why the US used very heavy shells with proportunately small filler.

I think this really comes down to two things. The 16" shell can penetrate more deck armor. I don't think that is in dispute. The German weapon can't penetrate the US ship's deck armor at any range.

What you are disputing is turret armor penetration. I submit that if a British 14" shell can't penetrate 18" of US class B armor at range 0, neither can Bismarck at any reasonable range because the shell will shatter or deform and ricochet.

[tommy303]

To expand some on what Bgile is saying, the USN used Ammonium Picrate as a filler while the Germans used preformed TNT/wax blocks. Ammonium Picrate, being a heavier compound, required less volume per weight than TNT, resulting in a smaller explosive cavity; it was also less prone to concussive shock than TNT and did not require the extra volume needed for a wooden shock absorbing block as was incorporated into German shells. The result was that while the weight of filler was almost the same in the German and USN shells, the volume of the explosive cavity was much larger in the German design, thus weakening the structural integrity of the German shell. On the plus side, the TNT charge was more powerful, both in terms of weight and potential explosive effect, provided the shell functioned properly.

[Dave Saxton]

You completely missed the point. It wouldn't penetrate at MUZZLE VELOCITY, which is much more energy than Bismarck's 15" at 20k yds. We have no reason to believe Bismarck's shells would perform better.

You may want to recant. This shows a lack of understanding of penetration dynamics when it comes critical velocities. I suggest perusung the primary document literature, such as ADM213/951, Calculations of Heavy Armour for Ships, GKdos100, and so forth..instead of taking a secondary source given in one context and appling it generally.

By using the penetration curves for the 38cm and plugging in the numbers for obliquity vs a 30* laid back surface, and the velocity numbers, we find that the face plate is partially penetrable out to about 31, 000 meters, and fully penetrable out to about 24,000 meters. That is long range.

There is no evidence that German shells had poor impact integrity, and it's bad science to infer the performance of a different sample to the German shells.

[Tiornu]

The impact on SoDak's barbette was about as close to 90deg as was possible at that range. The hit was dead-center on the barbette.

[Tiornu]

By using the penetration curves for the 38cm and plugging in the numbers for obliquity vs a 30* laid back surface, and the velocity numbers, we find that the face plate is partially penetrable out to about 31, 000 meters, and fully penetrable out to about 24,000 meters.

I'd be interested in hearing about this penetration curve for the 38cm shell against American armor. Is it available somewhere?

[Nlneff]

"I'd be interested in hearing about this penetration curve for the 38cm shell against American armor. Is it available somewhere?

All I can say is using Nathan Okun's M79APCLC (which is the relevant calculator, since its STS/Class B plate), given a 30 degree slope to the turret front plate, and a effective thickness of 18.5in STS plate, it looks like Bismarck can penetrate the front plate to just past 16000 yards (net obliquity 19.6 degrees, velocity is 1889, limit velocity is 1849, which suggests that ~16000 yards would a good bet for a used liner, according to M79APCLC.

When the US calculated the vulnerability for its faceplates there was a outer limit as well, as the plate became vulnerable to plunging fire, but it doesnt appear to become vulnerable again to the 38cm at any range.