From an outgrowth of the Graf Zep thread; Battle ship secondary armaments.
This is a complex question of fire control, throw weight, protection and a whole host of other things. But the main purpose of secondary armament is to provide air defense against dive bombers and torpedo bombers; and to provide defense against destroyers and fast attack craft.
There are two school of thoughts, of using dual purpose armaments (Like the US 5" guns and the British 5-1/4" guns) or having dedicated anti air and anti surface armaments (like the Riechelieu and the Littorio Class; whom specifically rejected dual purpose guns in light of their respective navies previous experience with them)
The lines are actually quite blurred as the Yamato's 155mm secondary guns are dual purpose, but can only elevate to 55 deg and have a RPM of 6; which is quite low for AA work - which is really more of a surface action gun. While the 105mm AA guns on the Bismark can engage both air and surface targets - which actually had a further range than the US 5" gun and a very similar ceiling.
Design considerations are also very different, European navies tend to optimize secondary armament against destroyers and FAC as the smaller Atlantic and Mediterranean, have so much more coast line for FAC and destroyers to lurk. Pacific navies, tend to be optimized against air craft as they are optimized for firing rate instead of being able to out range destroyer's own main guns. Of course, with dual purpose weapons comes the question about how much fire power to distribute to attacking aircraft and attacking FAC if so happen that they engage at the same time.
I am less concerned about fire control suites, and radar suits or specialist ammo like proximity fuse, because in most cases each belligerent have something that is equivalent; but did not have the capital or the need to deploy them. e.g. why spend money and resource on the Tirpitz when she is bottled in Norway; but for sure the FuMG 65 Würzburg-Riese which was accruate to 25 meters can be adapted for BB gun laying; and the Jagdschloss (i.e. the grand daddy of the phase array radar) be used for surface scanning. Similarly, Rheinmetall Borsig AG had developed proximity fuse for the 88mm AA.
I am also less concerned about light AA weapons, at the end of the war all, battleships are bristling with light AA weapons; the Tirpitz went from 12 2cm gun to 58; while the Yamato went from 24 25mm gun to 162 25mm gun. North Carolina went from 16 1.1 inch guns to 60 40mm gun and 46 20mm gun.
So looking at our favorite contestants:
- HMS King George V
- KMS Bismark
- USS Iowa
- IJN Yamato 1941
- IJN Yamato 1944
Driving away destroys and FAC before they can use their main guns and release their torpedoes – receiving non-penetrating hits can still rake up a battleship considerably destroying and damaging fire controls, exposed gun crews, radar and observation equipment, motor and aircraft launches; etc.
The US Fetchers DD with the 5” have a maximum surface range of around 16 km, torpedos, lets say have an effective range of 5 km and assuming a destroyer travels at 40 knots towards the battle ship across its side.
Well, since the US secondary weapons are destroyer weapons, they will therefore be in range at the same time when the destroyer’s gun come within range. Given that each shell can easily damage a destroyer, and the bismark and yamato can easily sink one with a 150mm or 155 mm shell (as per the table below, the muzzle energy of the 155 and 150 is significantly more powerful), KGV, Bismark and both version of the yamato can put up enough shells to sink a small flotilla of destroyers before having any chance of receiving damage.
Now consider that the british 4.5” can shoot out to 18,970 meters, and the Japanese 127mm gun can shoot out to 18,400 meters; i.e. technically, the US BB have a dead zone of around 3 km where “theoretically” destroyers can pepper US BBs where the slow firing main guns will find it hard to hit the small fast moving DDs while staying out of range of the BB’s secondary armaments.
Now anti-aircraft, which gun performance is important is rate of fire to fill the sky, good muzzle velocity so the shell reaches its target quickly, a good ceiling and a good bursting charge. No surprises that the US 5” is really good, being able to throw 150 rounds per minute into the air to one side of the ship. What is really surprising is that 10.5 cm can throw an impressive 288 shells into the air per minute; and most impressive of all, the 105mm’s bursting charge at 3.8kg is larger than the 5” bursting charge of 3.3kg. This shouldn’t be a surprise as how excellent the 88mm is in the AA role, and the 105mm is really just it’s bigger cousin.
Assuming that the explosive filler is equivalent, I used the only reliable data on lethal radius of the air burst – the Japanese 5” had a lethal radius of 18.8 meters with a 1.8kg bursting charge – linearized the volume of explosion to the mass of bursting charge; the Bismarck can put up more than double the lethal volume that Iowa can throw up. Where Iowa can throw up more than double that of KGV and Yamato. Yamato do better post refit, but still doesn’t match the AA throw weight of Iowa – note this is including the 155mm guns which can only elevate 55 degrees and have a slow firing rate.
To conclude, obviously every ship presented here is a mighty one and each was designed to fulfill a specific role under a different set of limitations. This analysis is devoid of things like fire control, AA fire control on the Bismarck and the Prince of Whales had teething issues. Some of these data collaborated with battle reports, like the Japanese 5” had a low ceiling and a weak punch, that given it’s slow velocity would make it harder to target fast moving planes. Anti-surface units – destroyer, frigates and FAC wise; Iowa is strangely weaker than the other contestants.
This is a complex question of fire control, throw weight, protection and a whole host of other things. But the main purpose of secondary armament is to provide air defense against dive bombers and torpedo bombers; and to provide defense against destroyers and fast attack craft.
There are two school of thoughts, of using dual purpose armaments (Like the US 5" guns and the British 5-1/4" guns) or having dedicated anti air and anti surface armaments (like the Riechelieu and the Littorio Class; whom specifically rejected dual purpose guns in light of their respective navies previous experience with them)
The lines are actually quite blurred as the Yamato's 155mm secondary guns are dual purpose, but can only elevate to 55 deg and have a RPM of 6; which is quite low for AA work - which is really more of a surface action gun. While the 105mm AA guns on the Bismark can engage both air and surface targets - which actually had a further range than the US 5" gun and a very similar ceiling.
Design considerations are also very different, European navies tend to optimize secondary armament against destroyers and FAC as the smaller Atlantic and Mediterranean, have so much more coast line for FAC and destroyers to lurk. Pacific navies, tend to be optimized against air craft as they are optimized for firing rate instead of being able to out range destroyer's own main guns. Of course, with dual purpose weapons comes the question about how much fire power to distribute to attacking aircraft and attacking FAC if so happen that they engage at the same time.
I am less concerned about fire control suites, and radar suits or specialist ammo like proximity fuse, because in most cases each belligerent have something that is equivalent; but did not have the capital or the need to deploy them. e.g. why spend money and resource on the Tirpitz when she is bottled in Norway; but for sure the FuMG 65 Würzburg-Riese which was accruate to 25 meters can be adapted for BB gun laying; and the Jagdschloss (i.e. the grand daddy of the phase array radar) be used for surface scanning. Similarly, Rheinmetall Borsig AG had developed proximity fuse for the 88mm AA.
I am also less concerned about light AA weapons, at the end of the war all, battleships are bristling with light AA weapons; the Tirpitz went from 12 2cm gun to 58; while the Yamato went from 24 25mm gun to 162 25mm gun. North Carolina went from 16 1.1 inch guns to 60 40mm gun and 46 20mm gun.
So looking at our favorite contestants:
- HMS King George V
- KMS Bismark
- USS Iowa
- IJN Yamato 1941
- IJN Yamato 1944
Driving away destroys and FAC before they can use their main guns and release their torpedoes – receiving non-penetrating hits can still rake up a battleship considerably destroying and damaging fire controls, exposed gun crews, radar and observation equipment, motor and aircraft launches; etc.
The US Fetchers DD with the 5” have a maximum surface range of around 16 km, torpedos, lets say have an effective range of 5 km and assuming a destroyer travels at 40 knots towards the battle ship across its side.
Well, since the US secondary weapons are destroyer weapons, they will therefore be in range at the same time when the destroyer’s gun come within range. Given that each shell can easily damage a destroyer, and the bismark and yamato can easily sink one with a 150mm or 155 mm shell (as per the table below, the muzzle energy of the 155 and 150 is significantly more powerful), KGV, Bismark and both version of the yamato can put up enough shells to sink a small flotilla of destroyers before having any chance of receiving damage.
Now consider that the british 4.5” can shoot out to 18,970 meters, and the Japanese 127mm gun can shoot out to 18,400 meters; i.e. technically, the US BB have a dead zone of around 3 km where “theoretically” destroyers can pepper US BBs where the slow firing main guns will find it hard to hit the small fast moving DDs while staying out of range of the BB’s secondary armaments.
Now anti-aircraft, which gun performance is important is rate of fire to fill the sky, good muzzle velocity so the shell reaches its target quickly, a good ceiling and a good bursting charge. No surprises that the US 5” is really good, being able to throw 150 rounds per minute into the air to one side of the ship. What is really surprising is that 10.5 cm can throw an impressive 288 shells into the air per minute; and most impressive of all, the 105mm’s bursting charge at 3.8kg is larger than the 5” bursting charge of 3.3kg. This shouldn’t be a surprise as how excellent the 88mm is in the AA role, and the 105mm is really just it’s bigger cousin.
Assuming that the explosive filler is equivalent, I used the only reliable data on lethal radius of the air burst – the Japanese 5” had a lethal radius of 18.8 meters with a 1.8kg bursting charge – linearized the volume of explosion to the mass of bursting charge; the Bismarck can put up more than double the lethal volume that Iowa can throw up. Where Iowa can throw up more than double that of KGV and Yamato. Yamato do better post refit, but still doesn’t match the AA throw weight of Iowa – note this is including the 155mm guns which can only elevate 55 degrees and have a slow firing rate.
To conclude, obviously every ship presented here is a mighty one and each was designed to fulfill a specific role under a different set of limitations. This analysis is devoid of things like fire control, AA fire control on the Bismarck and the Prince of Whales had teething issues. Some of these data collaborated with battle reports, like the Japanese 5” had a low ceiling and a weak punch, that given it’s slow velocity would make it harder to target fast moving planes. Anti-surface units – destroyer, frigates and FAC wise; Iowa is strangely weaker than the other contestants.
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