London & Washington era Heavy vs. Light Cruisers

[RETAC21]

16 hours ago, Argus said:

Yep and thanks for reminding me about the THRID thing I forgot to mention earlier

"Even if the enemy have a speed advantage it only rests on one shell not ended up in the wrong place, and until radar allowed blind fire though smoke chasing an enemy was no picnic. But the tendency was to turn and fight instead." 

Wut? not really, only if there was no other choice. Examples:

Schanhorst & Gneisenau:  

1) "Both battleships, accompanied by the heavy cruiser Admiral Hipper and two destroyers, sortied to attack convoys travelling between the Shetland Islands and Norway on 18 February 1940. This force was detected by the British soon after it sailed and the Home Fleet attempted to intercept it. No combat eventuated, and the German ships returned to port without having encountered any British shipping on 20 February."

2) Operation Berlin: Convoy HX-106 "Scharnhorst's crew spotted Ramillies at 9:47 am, and reported this to the flagship. In accordance with his orders to avoid engagements with powerful enemy forces, Lütjens cancelled the attack."

3) Convoy SL-67: "The German battleships searched for the convoy on 8 March, finding it at 1:30 pm. Lütjens attempted to attack at 5:30 pm, but broke off at high speed when Malaya was identified"

3) Admiral Hipper: https://en.wikipedia.org/wiki/Operation_Nordseetour

etc. Even Bismarck was trying to draw away from the British cruisers when met by Hood and Prince of Wales.

Auxiliary cruisers couldn't run away, but tried to pass as allied or neutral merchants, which was what Kormoran was trying to do when Sidney dropped by. Combat was the last choice of the raider captain vs an enemy warship, and even a merchant could be a problem, as Stier found SS Stephen Hopkins too much to handle.

[Yama]

On 1/12/2024 at 7:11 AM, Argus said:

Speaking about the Towns and later 'big' 6" cruisers, RN and USN alike, practically the range advantage of the 8" was moot, hit probabilities out at that distance were too low to covert theory into practice. By the time the 8" were in with a chance to get salvos to stick against ships maneuvering at 30 knots, the 6" were close enough that their rof gave them an equal chance of getting hits, and neither ship could shrug off 6", the odds running against whoever took the first hits. Sure the RN did a lot of missing at Matapan, the Italian cruisers were sensibly doing a very good job not letting them close the range. But 8" wouldn't have changed that picture for the better.  An 8" Mk.VIII takes 55.9 seconds to get a shell 25,000 yards down range, for a 30 knot ship that's 950 yards she's moved between bang and splash. The 6" Mk.XXII was a tad over 70 seconds, so more like 1200 yards run. But at 20,000 yards, the difference in target run over time of flight was down to a 150 yards between the two guns against the 2:1 advantage in rof (@ sustained rate) for the 6".... 

8" cruiser was not like to hit anything at 25 kyds, true, but that was quite long range even for battleships. Armour penetration of 6" shells was very poor at ranges over 15 000 yards - around 2 inches or less. Also, RoF advantage of smaller gun was obviously reduced at long ranges, when they had to observe fall of the shot.

[Argus]

3 hours ago, Yama said:

<snip> Armour penetration of 6" shells was very poor at ranges over 15 000 yards - around 2 inches or less. Also, RoF advantage of smaller gun was obviously reduced at long ranges, when they had to observe fall of the shot.

The penetration depends on which value you are looking at, belt/vertical penetration does go down, but deck/horizontal goes up (20,000 yards was about 40d angle of fall), and 6" fire was not really about armour penetration. The RN didn't even issue 6" AP most of the time, whatever SAP/CPC/HE being fired, it was about getting into the un-armored parts of the ship, generating cumulative dammage and ideally starting fires. 
The full spotting cycle with its slower ROF was only one mode of fire, once the directed thought it was 'on' they'd switch to rapid and adjust as required. Even at longer ranges where the 8" was superior in long range accuracy as an individual weapon, an extra 3 or 4 guns firing twice as fast over all filled the beaten zone better to a result that was on par or better in terms of hits per salvo. Yes the 6" was less effective but a 6" hit was a lot better than an 8" miss.  

[Argus]

9 hours ago, RETAC21 said:

"Even if the enemy have a speed advantage it only rests on one shell not ended up in the wrong place, and until radar allowed blind fire though smoke chasing an enemy was no picnic. But the tendency was to turn and fight instead." 

Wut? not really, only if there was no other choice. Examples:

Schanhorst & Gneisenau:  

1) "Both battleships, accompanied by the heavy cruiser Admiral Hipper and two destroyers, sortied to attack convoys travelling between the Shetland Islands and Norway on 18 February 1940. This force was detected by the British soon after it sailed and the Home Fleet attempted to intercept it. No combat eventuated, and the German ships returned to port without having encountered any British shipping on 20 February."

2) Operation Berlin: Convoy HX-106 "Scharnhorst's crew spotted Ramillies at 9:47 am, and reported this to the flagship. In accordance with his orders to avoid engagements with powerful enemy forces, Lütjens cancelled the attack."

3) Convoy SL-67: "The German battleships searched for the convoy on 8 March, finding it at 1:30 pm. Lütjens attempted to attack at 5:30 pm, but broke off at high speed when Malaya was identified"

3) Admiral Hipper: https://en.wikipedia.org/wiki/Operation_Nordseetour

etc. Even Bismarck was trying to draw away from the British cruisers when met by Hood and Prince of Wales.

Auxiliary cruisers couldn't run away, but tried to pass as allied or neutral merchants, which was what Kormoran was trying to do when Sidney dropped by. Combat was the last choice of the raider captain vs an enemy warship, and even a merchant could be a problem, as Stier found SS Stephen Hopkins too much to handle.

Sorry, I obviously wasn't as clear as I thought. The ships I had in mind were the raiders caught in distant waters who accepted action rather than tried to run; Graff Spee, Emden & Cap Trafalgar (arguably), K W de Grosse, Konginsberg (sort of). 
Your examples were S&G using their tactical initiative to pick and chose their engagements, not what I was trying to talk about. But you have me with Bismarck   I never think off her as a raider, and yep she ran and Prinz Eugene with her. 

[RETAC21]

12 hours ago, Argus said:

Sorry, I obviously wasn't as clear as I thought. The ships I had in mind were the raiders caught in distant waters who accepted action rather than tried to run; Graff Spee, Emden & Cap Trafalgar (arguably), K W de Grosse, Konginsberg (sort of). 
Your examples were S&G using their tactical initiative to pick and chose their engagements, not what I was trying to talk about. But you have me with Bismarck   I never think off her as a raider, and yep she ran and Prinz Eugene with her. 

No problem, I suspected I was missing the point

I rather think that the decision to engage was led by the classic "insufficient intelligence", ie, the raiders thought the enemy was weaker than it was (certainly the case with Graf Spee).

There's also luck. KMS Thor ran into 3 AMCs! It tried to outrun HMS Alcantara and when it couldn't, it disabled her and ran away; later on, she ran into HMS Carnavon Castle, which she engaged proving to be tactically superior and forced to disengage. 

Then she met HMS Voltaire - I guess by this point the Germans were quite confident and she engaged the AMC outright, sinking it.

[Yama]

On 1/15/2024 at 4:25 AM, Argus said:

I'll stand by my comment, as I worded it quite carefully. The sort of merchant shipping converted to raiders and AMC's were not EASILY killed with 6" guns. Provided the crew could keep the fires to a tolerable level and nothing got into a magazine or torpedo warhead (so essentially the same criteria as a proper warship). A big merchie or medium sized liner could and did absorb an immense amount of punishment, they sort of made up in reserve buoyancy and volume what they lacked in armor, to soak up the hits. The ships would die, but they died hard if the crew did their bit, eg Kormoran or Kaiser W d Grosse, even going up against 11" guns, look at Jervis Bay and Rawalpindi. 

True perhaps for patrol cruisers, but merchant raiders were tightly packed with various things which, if hit, would have catastrophic consequences. Two or three German merchant raiders blew up spectacularly when hit, and at least two (Stier and Kormoran) were lost to damage which would not have been serious for a real warship with protection and redundancy.

[Argus]

Thor did indeed drink deep of her luck

I agree insufficient intelligence was a factor as you suggest. But even if Harwood had only had a Leander and 2x H class destroyers under his command and a convoy to defend, Langsdorff would have still been better off avoiding the action if he could. As a raider engaging convoys is a mugs game; a/ you are doing the hardest part of the enemies job for them - pin pointing yourself, b/ face all the risks of engaging with escorts and/or defensive fire from the ships, c/ the inefficiency, better to stop 5 ships independently than have to sink the same number while fighting a battle. 

[Yama]

On 1/16/2024 at 7:37 AM, Argus said:

The penetration depends on which value you are looking at, belt/vertical penetration does go down, but deck/horizontal goes up (20,000 yards was about 40d angle of fall), and 6" fire was not really about armour penetration. The RN didn't even issue 6" AP most of the time, whatever SAP/CPC/HE being fired, it was about getting into the un-armored parts of the ship, generating cumulative dammage and ideally starting fires. 
The full spotting cycle with its slower ROF was only one mode of fire, once the directed thought it was 'on' they'd switch to rapid and adjust as required. Even at longer ranges where the 8" was superior in long range accuracy as an individual weapon, an extra 3 or 4 guns firing twice as fast over all filled the beaten zone better to a result that was on par or better in terms of hits per salvo. Yes the 6" was less effective but a 6" hit was a lot better than an 8" miss.  

Difference was not necessarily that big, as 8 inch shell was big enough that fragments from a near-miss could penetrate hull steel of an unarmoured ship, such as destroyer. As for the types of shells, you're right, however 'cumulative damage' would come to play only on large amount of hits, which were very difficult to achieve with 6-inch guns at ranges over 15 000 yards. In actual battles, hit rates may have been as low as 1 per 1000.

[CaptLuke]

On 1/11/2024 at 9:11 PM, Argus said:

Speaking about the Towns and later 'big' 6" cruisers, RN and USN alike, practically the range advantage of the 8" was moot, hit probabilities out at that distance were too low to covert theory into practice. By the time the 8" were in with a chance to get salvos to stick against ships maneuvering at 30 knots, the 6" were close enough that their rof gave them an equal chance of getting hits, and neither ship could shrug off 6", the odds running against whoever took the first hits. Sure the RN did a lot of missing at Matapan, the Italian cruisers were sensibly doing a very good job not letting them close the range. But 8" wouldn't have changed that picture for the better.  An 8" Mk.VIII takes 55.9 seconds to get a shell 25,000 yards down range, for a 30 knot ship that's 950 yards she's moved between bang and splash. The 6" Mk.XXII was a tad over 70 seconds, so more like 1200 yards run. But at 20,000 yards, the difference in target run over time of flight was down to a 150 yards between the two guns against the 2:1 advantage in rof (@ sustained rate) for the 6".... 

 

It may be worth expanding the conversation to take a couple of additional things into consideration.  Using the USN 8" Mk 12 vs. 6" Mk 16 as examples:

• The shell weight ratio for corresponding US land howitzers was roughly 2.1-1 (8" howitizer 203lbs vs. 6" howitzer 95 lbs) but for the naval weapons the 8" fired 335lb/152kg shell vs. the 6" 130lb/59kg, so a 2.6-1 advantage.  The ratio for the UK guns you used is similar: 256lb/116kg vs 100lbs/45kg, so again roughly 2.6-1   This goes a ways towards offsetting the rate of fire advantage for 6" guns.
   
• Your points about fire control are well taken but there is also the issue of flatter trajectories for the 8" giving a larger beaten zone.   At 16,000 and 20,000 yards, the US 8" was coming down at 17 degrees and 25 degrees, while the US 6" was coming down at 24 and 36 degrees.   So the 8" advantage, from a fire control perspective, is not just a time of flight reduction but also a greater beaten zone. 

I'm not arguing that these two things "prove" anything about the 6" vs. 8", just that they are worth throwing into the discussion.

[Argus]

3 hours ago, CaptLuke said:

It may be worth expanding the conversation to take a couple of additional things into consideration.  Using the USN 8" Mk 12 vs. 6" Mk 16 as examples:

• The shell weight ratio for corresponding US land howitzers was roughly 2.1-1 (8" howitizer 203lbs vs. 6" howitzer 95 lbs) but for the naval weapons the 8" fired 335lb/152kg shell vs. the 6" 130lb/59kg, so a 2.6-1 advantage.  The ratio for the UK guns you used is similar: 256lb/116kg vs 100lbs/45kg, so again roughly 2.6-1   This goes a ways towards offsetting the rate of fire advantage for 6" guns.
   
• Your points about fire control are well taken but there is also the issue of flatter trajectories for the 8" giving a larger beaten zone.   At 16,000 and 20,000 yards, the US 8" was coming down at 17 degrees and 25 degrees, while the US 6" was coming down at 24 and 36 degrees.   So the 8" advantage, from a fire control perspective, is not just a time of flight reduction but also a greater beaten zone. 

I'm not arguing that these two things "prove" anything about the 6" vs. 8", just that they are worth throwing into the discussion.

Point taken, but I think it worth note those USN guns are running 'super heavy' shells. Their older 260lb &105lb shells are closer to the norm. Doesn't change the essential point, but between nations, data sources and assorted variations there's enough mess in this field, I like to at least get the basic fruits lined up before chopping them into the salad

The 8" is a better gun taken on its own, and if like the USN towards the end of WWII you have an automatic one with a ship big enough for the magazines to feed the beasts, then there's just no argument - if you can have your cake and eat it too why not?  But that's the crux of it, there is no right answer because it shifts with context and technology, the key decisions that frame the ships are usually being made years if not decades before the systems got used for real, and the actual differences between comparable 6" and 8" is less than the variability of the battles they fought.

 

Edited January 18, 2024 by Argus