Secondary Battleship Batteries in WW2

[ScottyB]

IIRC, the Iowa's were originally designed for thirty 3/50's rather than their actual fit of 5/38's.

Fortunately, no one bought into that one...

 

I think the 5"/38's were in the original design, I have never read anything stating otherwise. The Iowa's were to get a bunch of 3"/50 rapid fire mounts to replace the 40MMs but that never happened as the ships were decomissioned before the money to do it was available.

 

Scott

[DesertFox]

According to NavWeap: 4.5 inch british secondard has a rate of fire of 12 rounds per minute and 5.25 have a rate of fire of 7 to 8 rounds per minute. Of course the 5 inch / 38 has a rate of 15 to 22 per minute.

[Shortround6]

Part of the debate is about the effectiveness of the few hits they thought they would get. With 88-90mm shells going about 20-25lbs and 100-105mm shells going just over 30lbs they didn't compare well to the 45-55lb 120-130mm guns in effectiveness per hit let alone the 88-105lb shells of the 150mm class guns. The higher weight shells tended to have longer effective range (longer danger space at given range) than the lighter guns.

[Scott Cunningham]

I would argue that the 5"38cal DP guns on the US battleships were THE decisive AA gun of the war (even moreso than the famed german 88). While the 88 made a name for itself more as an AT gun than as an AA gun, the 5" gun was decent in both roles. In surface engagements it worked well enough. In anti-aircraft mode, when coupled with the radar FCS and prox-fuze it was a battle winner. The US had a VERY effective layer of AA. It started with the deadly CAP's. After that was the 5" with prox fuze. That was backed up by the potent 40mm, and the last ditch (largely ineffective, but still useful) 20mm Oerlikons.

 

After the 5" came into widespread use in late 42, there were very few successful attacks on US task forces until the suicide attacks of 44-45. Hell, I think the South Dakota managed to get 27 air kills in one battle.

[Tony Williams]

According to NavWeap: 4.5 inch british secondard has a rate of fire of 12 rounds per minute and 5.25 have a rate of fire of 7 to 8 rounds per minute. Of course the 5 inch / 38 has a rate of 15 to 22 per minute.

Quite so: when I said that the 4.5" was "better" I was clearly comparing it with the 5.25". The higher rate of fire would have considerably increased the chances of scoring hits against any targets, and that would probably have made them better anti-destroyer weapons as well as AA guns. I think that only when moving up to cruiser-sized targets would the individual penetration and destructivenesss advantage of the 5.25" have taken over.

[Ken Estes]

Quite so: when I said that the 4.5" was "better" I was clearly comparing it with the 5.25". The higher rate of fire would have considerably increased the chances of scoring hits against any targets, and that would probably have made them better anti-destroyer weapons as well as AA guns. I think that only when moving up to cruiser-sized targets would the individual penetration and destructivenesss advantage of the 5.25" have taken over.

 

DK Brown wrote that the 5.25" was considered minimal at design time for inflicting damage on opposing destroyers, and the 4.5" was considered insufficient. He was, of course, not part of that deliberation and seemed to hold that the 4.5" ought to have been continued until the 5.25" bugs were worked out, cf. Vanguard. The 4.5" upgrades to the older battleships/battlecruisers were of course sorely needed in both DP categories and the 5.25" did not come into account with them.

[Tony Williams]

DK Brown wrote that the 5.25" was considered minimal at design time for inflicting damage on opposing destroyers, and the 4.5" was considered insufficient. He was, of course, not part of that deliberation and seemed to hold that the 4.5" ought to have been continued until the 5.25" bugs were worked out, cf. Vanguard. The 4.5" upgrades to the older battleships/battlecruisers were of course sorely needed in both DP categories and the 5.25" did not come into account with them.

Makes you wonder why anyone bothered to fit destroyers with 4.5-5 inch guns, or capital ships with secondaries of that calibre, doesn't it? (The US 5" L38 fired the same weight of shell as the RN 4.5") What sort of targets were they supposed to be shooting at, apart from aircraft? And to think that everyone criticised the Germans for being so stupid as to fit some of their destroyers with 5.9" guns....

[Assessor]

Makes you wonder why anyone bothered to fit destroyers with 4.5-5 inch guns, or capital ships with secondaries of that calibre, doesn't it? (The US 5" L38 fired the same weight of shell as the RN 4.5") What sort of targets were they supposed to be shooting at, apart from aircraft?

 

Motor torpedo boats etc, especially in relatively narrow seas where room to manouver might be at a premium? This a suggestion / guess, but presumably being able to obliterate an MTB at longish range might be considered quite desirable.

[hojutsuka]

Makes you wonder why anyone bothered to fit destroyers with 4.5-5 inch guns, or capital ships with secondaries of that calibre, doesn't it? (The US 5" L38 fired the same weight of shell as the RN 4.5") What sort of targets were they supposed to be shooting at, apart from aircraft? And to think that everyone criticised the Germans for being so stupid as to fit some of their destroyers with 5.9" guns....

With all due respect to DK Brown, I think he was comparing apples to oranges when he pointed out that 4.5" was used to arm destroyers while 5.25" was considered a minimum as battleship secondary armament against destroyers. The scenarios are completely different.

 

Consider a battleship encountering a destroyer. The destroyer will try to use its speed to close as fast as possible until it can fire its torpedoes, then disengage. The battleship's main concern is to avoid being damaged or sunk, so the battleship needs to cripple or sink the destroyer before it can launch its torpedoes. This means the battleship needs to hit the destroyer at long range (before it can get within torpedo range), in a limited time with the range changing rapidly (as the destroyer is likely to be using its speed to close the range as fast as possible). This heavily favors the bigger gun with its flatter trajectory giving better chance of hitting even with rapidly changing range. Just getting hits is not sufficient for the battleship; the battleship needs to cripple the destroyer so it can no longer threaten the battleship with its torpedoes. Since the engagement time will be short, the number of hits is likely to be low, so a bigger gun which can do more damage with each hit is once again favored.

 

Now consider two destroyers encountering each other. The fighting will be at close range because WW II destroyers were too small to make stable gun platforms (the Germans found this out when they armed their destroyers with 5.9" guns but found that they could only fight effectively within the range of British destroyers armed with 4.5" guns). The fighting will go on until one side starts to get the worst of it and tries to disengage. Even then, the other side are destroyers too, so can pursue and prolong the engagement. So the 4.5" gun in a destroyer can get hits at the short ranges of a destroyer vs. destroyer fight, and even if each hit does less damage than a heavier shell, the high rate of fire of the smaller gun at short range combined with the longer expected time of engagement mean that the cumulative effect of multiple hits would likely prove fatal for its opponent.

 

So does this mean that 5.25" was a better secondary armament for a battleship than the 4.5" ? No, because the whole point of a DP secondary armament is to maximize capability against both air attacks and torpedo attacks within a limited displacement. With hindsight, we can see that air attacks were far more dangerous than destroyer torpedo attacks, so a secondary armament that had more capability against air attacks was preferable even at the cost of reduced capability against destroyer attacks. But in the mid 1930's when the British battleships of KGV class were being designed, the enormous strides that air power was to make in WW II was barely in the bud (the Gloster Gladiator, a biplane fighter, was first ordered for RAF in 1935 and became operational in 1937), so it is understandable that British designers of KGV class changed the original planned secondary armament of 4.5" guns to 5.25" guns, especially as the 5.25" guns were not yet in service and therefore no one knew of the problems that would plague it in the AA role.

 

Hojutsuka

[Tiornu]

In addition, the 5.25in gun never earned criticism for its anti-ship performance--at least none that I have found. On the contrary, the reports I've read gave it good grades. But personally I still prefer the 4.5in gun.

[DougRichards]

Makes you wonder why anyone bothered to fit destroyers with 4.5-5 inch guns, or capital ships with secondaries of that calibre, doesn't it? (The US 5" L38 fired the same weight of shell as the RN 4.5") What sort of targets were they supposed to be shooting at, apart from aircraft? And to think that everyone criticised the Germans for being so stupid as to fit some of their destroyers with 5.9" guns....

 

The Type 14 Blackwood frigates of the Royal Navy designed in the 1950s were armed exactly under that philosphy, they were intended to be cheap and cheerful ASW convoy escorts, so the only AA or surface warfare weaponry they carried were a brace of 40mm Bofors. They stayed in service through the Cod Wars until the mid 1980s.

 

Of course the classic example of mixed secondaries was the Yamato, with, as designed 12x6" and 12x5"AA, later changed to 6x6" and 24x5". Would probably have been much better off with around 30x5" DP to start with, excepting of course 18" shells are a bit of overkill against cruisers.

[Shortround6]

Somethings to consider when comparing battleship secondaries to destroyer guns is that the heavier 5.9-6in shells are much harder to handle on a rolling, pitching destroyer than on a more stable battleship so that the theoretical rate of fire fell of faster in the destroyers armed with big guns in a seaway.

Another thing is the the fire control arrangements between the two types of ships. Some between the wars destroyers were lucky if they had 9 ft range finders and their gun directors were probably located closer to sea level than the battleships secondary directors. Both factors limit the maximum practical engagement range regardless of the maximum range of the particular gun. Large, long barreled guns also had problems with inertia and in hand worked mountings were difficult to keep on target when tracking fast moving, zig-zagging targets. Powered mountings help a lot but the bigger guns mountings were not stabilized and trying to chase roll, pitch and yaw in addition to target movement might favor the medium guns, at least in keeping up a good rate of fire.

Edited January 7, 2010 by Shortround6

[Ken Estes]

....

 

Of course the classic example of mixed secondaries was the Yamato, with, as designed 12x6" and 12x5"AA, later changed to 6x6" and 24x5". Would probably have been much better off with around 30x5" DP to start with, excepting of course 18" shells are a bit of overkill against cruisers.

 

Sorry, but you are not going to hurt cruisers very much with 5" guns, exploits of Samar and 1st Guadalcanal notwithstanding. An intact CLAA working over an opposing cruiser might disable it, but that caliber remains underkill vs. 10,000 tonners.

[DougRichards]

Sorry, but you are not going to hurt cruisers very much with 5" guns, exploits of Samar and 1st Guadalcanal notwithstanding. An intact CLAA working over an opposing cruiser might disable it, but that caliber remains underkill vs. 10,000 tonners.

 

I know that about the 5", I was referring to the 6" guns as being against targets that the 5" were less than capable of dealing with, but not justifying firing 18" shells at.

[Tony Williams]

With all due respect to DK Brown, I think he was comparing apples to oranges when he pointed out that 4.5" was used to arm destroyers while 5.25" was considered a minimum as battleship secondary armament against destroyers. The scenarios are completely different.

 

Consider a battleship encountering a destroyer. The destroyer will try to use its speed to close as fast as possible until it can fire its torpedoes, then disengage. The battleship's main concern is to avoid being damaged or sunk, so the battleship needs to cripple or sink the destroyer before it can launch its torpedoes. This means the battleship needs to hit the destroyer at long range (before it can get within torpedo range), in a limited time with the range changing rapidly (as the destroyer is likely to be using its speed to close the range as fast as possible). This heavily favors the bigger gun with its flatter trajectory giving better chance of hitting even with rapidly changing range. Just getting hits is not sufficient for the battleship; the battleship needs to cripple the destroyer so it can no longer threaten the battleship with its torpedoes. Since the engagement time will be short, the number of hits is likely to be low, so a bigger gun which can do more damage with each hit is once again favored.

The US seemed very happy to fit its battleships with 5" L/38 as a secondary weapon. If this is inadequate against destroyers, I can only assume that the battleships were meant to use their 16" guns against them?

[Shortround6]

I would imagine that in a battleship vrs destroyer situation the battleship would use it's main guns to defend itself in addition to the secondaries, ammo supply permitting.

 

If part of a fleet action in which the main guns were engaging the enemies heavy units the secondaries are their own against destroyers, of course in a fleet action the Battleships own escorting light cruisers and destroyers should have thinned their numbers a bit.

 

Germans may have used separate 5.9in and 4.1in batteries as much for the commerce raiding roll. Trying to save main battery ammo while still mounting an effective anti-merchant ship armament?

[shep854]

The US seemed very happy to fit its battleships with 5" L/38 as a secondary weapon. If this is inadequate against destroyers, I can only assume that the battleships were meant to use their 16" guns against them?

 

Wouldn't the BB's greater stability permit accurate 5" fire further out, closer to the gun's theoretical 18000yd effective range? Also, could the main directors be used to direct the secondary batteries in a surface engagement?

[Guest aevans]

Wouldn't the BB's greater stability permit accurate 5" fire further out, closer to the gun's theoretical 18000yd effective range? Also, could the main directors be used to direct the secondary batteries in a surface engagement?

 

The 5" and 16" guns used different computers that were hardwired to the directors. This is back in the days when computers were made out of cams, gears, and relays, remember. The ballistic characteristics of the gun being directed were physically built into the machine.

 

As for the question of stability, I think th fire control systems were responsive enough that they could adequately compensate for the motion of any platform.

[ScottyB]

The 5" and 16" guns used different computers that were hardwired to the directors. This is back in the days when computers were made out of cams, gears, and relays, remember. The ballistic characteristics of the gun being directed were physically built into the machine.

 

As for the question of stability, I think th fire control systems were responsive enough that they could adequately compensate for the motion of any platform.

 

I believe the MK37 directors were capable of controling the 16" guns as well as the 5"/38s. My best friend said the Iowa haa a huge switchboard that allows the directors and mounts to be matched up. I concur with you about the FC systems and stability.

 

Scott

Edited January 9, 2010 by ScottyB

[Guest aevans]

I believe the MK37 directors were capable of controling the 16" guns as well as the 5"/38s. My best friend said the Iowa haa a huge switchboard that allows the directors and mounts to be matched up.

 

From what I've read, each stable element had to be calibrated for the difference in position between itself and the director it sent leveling instructions to. (The sights and rangefinders had to be corected as well as the gun mounts, or the director crew would have been spending all of their time trying to maintain line of sight with the enemy vessel or aircraft.) The stable elements were in turn mechanically linked with the fire control computer. It couldn't provide accurate leveling commands to a director it wasn't calibrated for, or to a type of gun that the computer it was connected to couldn't control. The switiching system your friend told you about was probably for assigning 5"/38 mounts to directors.

[JOE BRENNAN]

Wouldn't the BB's greater stability permit accurate 5" fire further out, closer to the gun's theoretical 18000yd effective range? Also, could the main directors be used to direct the secondary batteries in a surface engagement?

On the first question, I would guess yes in certain circumstances. In USN ops in Pacific relatively few (hard to recall any offhand) surface actions were fought in really rough conditions. But there was some motion limit beyond which both fire control and eventually, physical operation of the guns became difficult. Considering actions like the chase by British cruisers of German DD's in Bay of Biscay in late '43, where the ships were suffering extreme motion at high speed in very rough seas, a BB, all else equal, ie if it were as seakindly for its size, would move less, have lower accelerations specifically. But in general for engaging DD's at ~18k yards (or more) just using the main battery would be more likely, as in USS Massachusetts v French DD/super-DD's at Casablanca, landing hits on them at long range (along with hits from US cruisers).

 

On second, yes to some degree and some cases. On USN fast BB's of WWII the fire control switchboards were by 1944 set up for the secondary battery fire control computers to receive train and radar range data from the main battery director. This was not the case originally, apparently. This is described in action reports from BB's in "Operational Experience of Fast Battleships" by the Naval Historical Center. In other direction, the main battery from the start could be controlled from a secondary battery director, on USN WWII cruisers and BB's, to enable long range barrage AA fire with the main battery, though the USN (in contrast to the IJN) seldom if ever employed such tactics in combat. In that case, arbitrary spot corrections were cranked into the secondary battery fire control computer. This is described in manuals for those systems.

 

Joe

[hojutsuka]

The US seemed very happy to fit its battleships with 5" L/38 as a secondary weapon. If this is inadequate against destroyers, I can only assume that the battleships were meant to use their 16" guns against them?

Perhaps I did not make my point clear?

 

My post #34 was principally concerned with pointing out that comparing the size of guns desirable for a destroyer with the size of secondary armament guns desirable for a battleship is comparing apples to oranges even though both guns may be required to target enemy destroyers, so that it was not unreasonable for RN ship designers in 1935 to have felt that 4.5" was adequate as destroyer armament while at the same time feeling that 4.5" was too small as battleship secondary armament.

 

Perhaps another example will make it clearer. At the end of World War II, British fighter armament was beginning to converge to 4x20mm, which was seen as powerful and fast-firing enough to deal with both bombers and fighters. As shipboard AA, the British felt that 20mm was not powerful enough and replaced it where ever possible with bigger weapons like the 2pdr or the 40mm Bofors. The target in both situations were the same (enemy aircraft) but the different scenarios in which the 20mm guns were employed meant that in one role they were considered optimal and in the other not powerful enough, and rightly so.

 

I did not claim that 4.5" (or 5") was inadequate against destroyers. In fact, I pointed out in my post #34 that with hindsight 20x4.5" would have been a better secondary armament for the KGV class than the real life 16x5.25" when considering AA as well as anti-destroyer role. But I do feel that those British warship designers who considered 5.25" minimal as anti-destroyer armament for battleships had reasonable grounds for feeling that destroyer armament and battleship secondary armament were separate roles, so that dismissing them as fools by saying that 4.5" was considered adequate for destroyers is hardly warranted.

 

As for the USN and the 5"/38, what is adequate against destroyers is a judgment call since the limitations in size means that every feature of a battleship is a matter of compromise. So why should we be surprised that the USN did not choose the exact same caliber as the RN? Especially when you consider that historical data played a major role back then in a navy's decision on what was adequate. The RN could look back to World War I when 6"-5.5" guns were felt to be necessary for battleship secondary armament, and destroyers had grown larger and tougher since then. The USN battleships had traditionally used 5" guns (actually 5"/51) for anti-destroyer armament for battleships, so quite reasonably they were willing to accept 5"/38 (which was admittedly a bit less powerful than the 5"/51, but was useful against aircraft as well). And note that the USN was not perfectly satisfied with the anti-surface performance of the 5"/38. During World War II, the USN started to develop a more powerful secondary weapon specifically to improve anti-surface performance. This was the 5"/54, which was very close to the British 5.25" (70lb shell at 2650 feet/sec as opposed to the 5.25", 80lb shell at 2672 feet/sec) and which was planned to be the secondary armament for the Montana class battleships, as well as being used for the Midway class carriers and becoming the main armament of post-WW II US destroyers.

 

Hojutsuka

[Scott Cunningham]

In the end, it was AA performance that mattered. I think every battleship used its guns in the AA role. I am hard pressed top think of any that used their secondaries in the surface role (maybe some at Guadalcanal) other than for shore bombardment (*where it wasn't critical)