AHC/WI: More Atlanta/Juneau Class Ships

The Didos had fewer, heavier but slower firing guns; better for surface action, but not as good in their designed purpose.
IIRC part of the reason for slow firing was the cramped gun-houses, as I understand it the slightly updated and enlarged ones on the post-war HMS Vanguard saw a fair improvement. Of course that's not to say that there weren't other factors such as ammunition hoists and rammers/loaders but space was an issue apparently.

Tony Williams did suggest a fair while back that the British would have been better off concentrating on just the 4-inch gun in twin mountings and the 4.7-inch gun in the 4.5-inch's high-angle twin mountings with a re-designed shell rather than the plethora of calibres they had in the 1930s and '40s. I don't remember the exact figures but size and weight-wise I believe it would have been enough to fit two extra twin mounting onto the Dido-class, at which point it starts getting much nearer to the Atlanta-class.
 
IIRC part of the reason for slow firing was the cramped gun-houses, as I understand it the slightly updated and enlarged ones on the post-war HMS Vanguard saw a fair improvement. Of course that's not to say that there weren't other factors such as ammunition hoists and rammers/loaders but space was an issue apparently.

Tony Williams did suggest a fair while back that the British would have been better off concentrating on just the 4-inch gun in twin mountings and the 4.7-inch gun in the 4.5-inch's high-angle twin mountings with a re-designed shell rather than the plethora of calibres they had in the 1930s and '40s. I don't remember the exact figures but size and weight-wise I believe it would have been enough to fit two extra twin mounting onto the Dido-class, at which point it starts getting much nearer to the Atlanta-class.

A lot of work had gone into the Twin 4.7 mount in the early / mid 30s only for the purse strings to be cut before work had finished on making it a good HA Gun - Tonys Suggestion IIRC was that for a little bit more work / money it could have been made into a much better HA gun as well (as good as the 4.5 twins) and his ultimate suggestion was to use this 'superior' Twin 4.7s as a replacement for the OTL 4.5, 4.7 and 5.25 mounts where used - with the 4" Twin still used as OTL.

That being said two of the considerations for the 5.25" was that aircraft where flying higher and higher and in the 30s where it was beleived that "the bomber will always get through" it made sense to have a weapon system not made obsolete by aircraft that could fly above its effective engagement altitude.

The expected threat to the RN operating in a littoral environment was throught to be 2 and 3 Engined bombers.

While single engined dive bombers (Mainly JU87s) did prove to be a serious threat the majority of attacks launched at the RN in the Med were by twin and triple engined bombers.

Also with ship launched torpedo ranges increasing a better weapon for engaging destroyers was required as a secondary weapon for BBs (4.5 was too short ranged and 6" too large and slow firing and not very good as a secondary AAA).

Im not suggeting that the Atlantas would have been bad in any of these 'other role' roles but part of the success of the 5"/38 was reliable proximity fused shells (so 1943+) coupled with its higher ROF (helped by a very well designed shell room and gun house) as an AAA weapon this is not the preceived primary role of the class. It was to act as a scout leader for a Destroyer Flottila.

That it happened to be very good as a AAA Ship and avaialble as that threat emerged was a happy coincidence.

Handsome ships as well IMO
 
The other factor of 4.7-inch versus 5.25-inch is of course surface warfare - whilst you can argue that increased rate of fire results in a greater throw weight the issue of the dimensions of the individual shells carries, if you will forgive the use of the term, a weight all of its own. I'd expect you to have a hard time convincing the Admirals that anything less than a 5-inch gun would be powerful enough against a battleship. Realistically I think the best you could do would be to generally standardise on the 4-inch and 4.7-inch twin mounts but keep the 5.25-inch guns for the battleships. Of course one knock-on of all this could be that if the 4.5-inch is ignored it might potentially mean you don't see the 3.7-inch Mk VI anti-aircraft gun which would be a serious loss. I think we might be drifting from the original topic though. :)
 
The 4.5 inch DP as fitted to two of the Dido's, Renown and some other ships actualy threw a heavier weight of shell at a higher rate of fire than either the 4.7" or 5.25 mounts when using seprate ammunition. If this could have been rolled out as a standard gun for all DP mounts from the mid 1930's onwards then their might have been some benefits for the RN.
(shell weight for each calibre 4.5"= 86lb. 4.7"= 50lb. 5.25"= 80lb)
 
The 4.5 inch DP as fitted to two of the Dido's, Renown and some other ships actualy threw a heavier weight of shell at a higher rate of fire than either the 4.7" or 5.25 mounts when using seprate ammunition. If this could have been rolled out as a standard gun for all DP mounts from the mid 1930's onwards then their might have been some benefits for the RN.
(shell weight for each calibre 4.5"= 86lb. 4.7"= 50lb. 5.25"= 80lb)

Oh I agree with Hindsight the Twin 4.5 might have been a better choice as a true universal DP gun but lets not forget the later MkXI 4.7s could reliably pentrate the armour (Up to 3") on most Cruisers at 10 KMs while still retaining a useful AAA Ability and a high ROF

In fact with hindsight equip everything smaller than a Town /Crown or Minator with the 4"/45 twins after 1936 - and lots of them :D
 
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