6-inch semi-auto gun superior to 8-inch gun for cruisers?

The non-rapid firing 8-inch gun for cruisers was basically as slow to reload as a 14-inch battleship gun. With six-inchers, the Japanese had something similar to the US Mk 16 6/47, which was semi-automatic, with three times the rate of fire of the 8-inchers.

At Savo, 8-inch guns (from Chokai, Kako, Aoba) were predominant in sinking the Allied cruisers. At Cape Esperance and first Guadalcanal, the 6-inch with SG radar proved its effectiveness in close night action.Then, the 6/47DP gun can also be used for anti-aircraft.

Would you fit your entire cruiser fleet with semi-auto 6-inchers?

 

Neither.. A balance is needed. Sometimes one will need the penetration of the 8". Where the 6" is needed is in engaging destroyers, which are fast and agile. Guns with a rapidity of fire can adjust quicker.

 

^
And maybe if ever your cruiser has to (heavens forbid) trade shots with an honest-to-goodness battleship.

 

Not sure where you got your information on Japanese guns from, but it is incorrect.

On the average, rounds per minute was thus:
Battleships. 1-2
8-inch cruisers. 3-4
6-inch Japanese. 5
6-inch American. 8-10

Also benefiting the Brooklyn clad was the ability to fire the super-heavy 6-inch AP, which gave roughly twice the penetration of the Omaha's 6-inch regular AP.

The Japanese might have achieved 7 rounds per minute, but the powder hoist could only move 5 powder bags per minute.

Also, range factored into the Japanese decision, so as to out distance the Americans.

As such, the 6-inch vs 8-inch decision is much more clear for the Americans and far less for the Japanese.

Edit:
As to American 6-inch AA capability, it was more potential than actual. The guns had the ability to elevate to 60 degrees, but the gun port openings only allowed for an elevation of 41 degrees. Only late in the war were the gun port openings elongated to allow the guns to elevate to their maximum of 60 degrees. However, firing at 60 degrees reduced the rounds per minute to 5, because their maximum loading angle of 20 degrees. Also, the turret train rate was ineffective against crossing targets.

 

..more ship to ship naval battles in the beginning compared to later when air power was the main killer ...so, the Japanese would want the best anti-air gun later in the war, correct? [ or even from the beginning? ] where as the US usually had air superiority ...

 

"The Japanese might have achieved 7 rounds per minute, but the powder hoist could only move 5 powder bags per minute."

This is one thing that stymies me. Rate of fire seems to be tied to this ability to hoist ammo from the magazine. But it's not an absolute limit. Gunners continually hoist ammo, even when there's no firing (or when firing is sporadic.) Therefore, actual rate of fire may be higher due to stock on hand available for loading.

 

Stocking powder bags is not a good idea.

 

AA was certainly a concern, but not that relevant to the 6- or 8" main battery issue. Several navies tried to endow their 6" or 8" guns with AA capability, mainly high elevations, but they were minimally effective.

Cruiser Maya had her #3 8" turret - the one with the poorest arc of fire - wrecked by a bomb in 1943, and it was replaced by two additional twin 5" mounts. This may have just been because of the difficulty of replacing an 8" turret, but it also showed an understanding of the importance of AA firepower. Some sources describe this as Maya being converted to an antiaircraft cruiser, but her new armament of eight 8" and twelve 5" was fairly typical for a heavy cruiser.

 

I'd agree a mixed force was best, though it's still challenging to get the right ships in the right place. One of the principal advantages of 8" over 6" gun cruisers was range, which is mostly relevant to daylight action, but both USN and IJN found themselves using heavy cruisers in the night battles around Guadalcanal.

The large 6" cruisers like the Brooklyn class proved very effective, but they were an artificial development based on treaty restrictions. The Brooklyns were a response to the Mogamis, which were designed for conversion to 8" guns as soon as the treaty limits lapsed; they might have been just as valuable or more so with their original 6.1" armament.

 

Actually, it is more or less an absolute limit. Simply because there is not enough room in the turret to stock additional shells and powder.

Perhaps, you are thinking of the powder & shell flat within the turret, but below the gun house, think of this as ready ammunition storage. The shells & powder were hoisted from the magazine to the shell & powder flats inside the turret, and the from the flats to the guns.

As has been pointed out, it was very dangerous to have excess powder & shells laying about in the gunhouse.

 

..and I thought there were night battles farther up the Solomons, also ...?--but those were more often destroyer battles?

 

On the Japanese side they were almost entirely destroyers or the old light cruisers they used as squadron flagships. On the US side several actions involved light cruisers, largely because of the losses of heavy cruisers in the Guadalcanal battles

At Cape Esperance the IJN again committed two heavy cruisers; apparently the landing close to Rabaul was considered sufficiently critical to justify it. The USN had its first division of four Cleveland class CLs, which had fortunately arrived in theater a couple of months earlier; every other Allied cruiser in surface action in the Solomons had been sunk or crippled.

There were a number of all-destroyer battles too, including two of the USN's famous successes at Vella Gulf and Cape St. George.

 

I'm confused, I thought Cape Esperance was fought on 11-12 Oct 1942 and the US had San Francisco (8" New Orleans Class CA), Boise (Brooklyn Class 6" CL), Salt Lake City (8" Pensacola Class CA) and Helena (another Brooklyn Class 6" CL) vs Japan's Furutaka, Aoba, Kinugasa all 8" (actually 7.9") cruisers.

The USS Cleveland, the first commissioned Cleveland class CL didn't start its first deployment until 10 October 1942 when it sailed for Bermuda then to North Africa. Columbia, 2d in the class didn't deploy until 9 November 1942 on her way to the Pacific. Four Cleveland's were involved in the Naval Battle of Empress Augusta Bay on 1/2 November 1943 near Bougainville; (USS Montpelier, Cleveland, Columbia, and Denver) vs 2 Japanese 8" Cruisers and two 6" light cruisers. I think this is the engagement you are referring to.

 

Yes, I meant Empress Augusta Bay. Thanks for the correction.

 

I figured as much because you mentioned the proximity to Rabaul and Bougainville is mighty close.

 

Two things.

First, in answer to the original question, a mix is best. Depending upon the tactical situation you might need the range and punch of the 8" and/or the volume of fire of the 6". In most situations both types are advantageous.

Secondly, a question arises in regard to US cruiser development. The Brooklyn's were good capable ships, they led to the Cleveland's which most experts consider the best light cruisers of the war. The Cleveland's had a sub-class the Fargo's that were completed with a more compact superstructure and single funnel to improve AA arc's. All excellent ships.
The one-off CA-45 USS Wichita armed with 9 x 8" guns in three triple turrets, on an improved Brooklyn hull was the basis for the Baltimore class. The Baltimore's are generally regarded as the best heavy cruiser class of the war. They had the Oregon City sub class that like the Fargo's were completed with a more compact superstructure and single funnel to improve AA arc's. The Baltimore's led to the Des Moines class, two of which were laid down before the wars end, and three of which were completed immediately after the war. The Newport News CA-148 served continuously for 25.5 years and gave good service as a naval gunfire platform off Vietnam. Though too late for WWII they were excellent ships.

The Atlanta class light cruisers were originally envisioned as flotilla leaders but ended up serving more in the AA escort role. They were fairly well armed with heavy AA, having the 5"/38 in 8 twin mounts for a total of 16 tubes (the same as the USS South Dakota BB-57, it being fitted as a flagship. Her sisters still had twenty guns in ten mounts like all the other US fast battleships). They were, not able to be used to their fullest potential because they had only two Mk37 directors. They were also extremely vulnerable in surface actions and were very top heavy and crowded. Some of this was corrected in the Oakland sub-class. The two wing turrets were deleted which helped the top weight and crowding. The following Juneau class were commissioned as the war ended or shortly thereafter. Like the Oregon Cty and Fargo sub-classes they had a more compact superstructure that decreased topweight and improved LOS.

So, what in the world were they thinking with the Worchester class? RF 6" guns in twin turrets with a layout similar to Juneau's.

 

I'm sure you can appreciate the value of automatic loading, dual-purpose 6" guns, something the Navy had been working on since the late 1930s, so I suppose the question would be why make the platform for them so large? It's one I would ask also; 14,700 tons is certainly pushing the limits for a "light" cruiser!

I've always thought an eight-gun ship of more conventional size and design would have made more sense. It would still put out more 6" firepower than a Cleveland. I wonder if it might have been possible to redesign some of the later Clevelands. The twin 6" turret was heavier than the triple, but the 5" battery would be omitted, or replaced by the new automatic twin 3"/50s, in which case the 40mms could be deleted (3"/50s in #1 and #6 positions on the centerline fore and aft would be particularly valuable). Weight/topweight would also be saved by eliminating the Mark 34 main armament directors; the Worcesters used their Mark 37s for surface fire control, augmented by a couple of Mark 13 radars.

Speaking of directors, the Worcesters had no fewer than four Mark 37s, enabling them to conduct three air engagements on either broadside. An eight-gun ship could made do with two, as in the Clevelands.

 

I'm glad you replied! I was hoping either yourself or Takao would. (Huge knowledge base and great at converting the data into useable information).
The Navy was developing the 5"/54 Mk 16 (15-18 rpm) as the replacement for the 5"/38, it had been planned as the secondary armament on the Montana's but was still not auto-loading. The 3"/50 Mk 22 was being developed to replace the 40mm bofors so you'd think the next logical step in evolution, if you were wanting an AA type cruiser would be 5"/54 twin mountings, with a Juneau layout, on an improved Cleveland hull and 3"/50 secondary/medium AA suite. The 6"/47 Mk 16 DP turret while having good train and elevation rates only ever realized a (ROF) of 9-10 rpm. The 5"/54 Mk 18 auto-loading gun in lightweight turret Mk 42 was further developed alongside the 3"/70 Mk26 and fielded in 1953, IIRC. (This is the progenitor of the 5"54 Mk 19 in Mk 45 lightweight mount and the Mod 4 with a 62-caliber barrel is the standard US Navy deck gun).
Now, immediately post-war the US Navy was beginning to realize that AA guns were not going to be adequate against the high-speed jet aircraft coming into service and began to focus on missiles. Would it not have made more sense, on a ship that size, to mount 2 x 5"\54 twin turrets, one fore and one aft and missiles in 2-3-4-5 turret positions? (Actually the 3 and 4 positions being super firing might have been better). The Terrier was first launched in 1953.

 

Thanks, I enjoy chatting with you also. There was some thought that the range of the 6"/47 might be needed to deal with fast aircraft or guided missiles, but the 5"/54 had comparable range and muzzle velocity, so I'm inclined to agree with you. You probably know there were a couple of 5"/54 cruiser designs, basically enlarged/improved Atlantas, but they never went forward. They included the two midships mounts which I also question the value of.

The key point of the 3"/50 was that it was the smallest weapon at that time that could accommodate proximity fuses; this plus range were its advantages over the 40mm. The Navy had hoped to replace two 40mm with one 3", but it ended up being more like 2.5:1, so there wasn't much gain in weight of metal.

You may recall from some of our earlier discussions of AA escorts that I like an eight-gun ship, two twin DP mounts and a heavy multiple automatic weapon at each end, and of course two DP directors. I'd call it a large destroyer, but one might say small cruiser.

The USN in WWII was starting development of surface-to-air missiles, but that might be a different topic from designing the 1940s generation of gunnery ships. Operational missile ships didn't go to sea until 1956 (cruisers Boston and Canberra) and ships designed as such until 1960 (Farragut/Coontz class DLGs, Adams DDGs). Numbers of missile launchers were not as significant as directors. Prior to Aegis, missile engagements required a director locked onto a target from before launch until detonation and confirmation of destruction of the target. USN practice was to provide two directors per launcher, plus search radars. Electronic systems and a Combat Information Center required interior space, causing ships to become "volume critical". Early missiles like Terrier, Talos, or Seaslug also needed large spaces for final assembly and checkout of the weapons before loading onto the launcher. Just a gun mount and a launcher at each end could require a cruiser-sized ship.

 

Agreed. What is interesting is that when it reached its developmental apex in the 3"/70 it was only used on a few ships.

One of your earlier points was the large size of the 6" twin mount Worchester, that's why I suggested a Cleveland hull. It is smaller and that's not subtracting the weight or four triple 6" turrets and barbettes. I still don't see why the Navy pursued the 6" twin and actually produced a class using a gun that had a lower ROF than the 5"/54 and laid it out in a similar manner to its least capable light cruiser class.
I was not aware of the Navy providing two directors per missile launcher.