Comments by "Steve Valley" (@stevevalley7835) on "The History and Development of the 5"/38 - Turns out you can take the sky from someone" video.

  1.  @pedenharley6266  In the late 30s, several old C Class (older than Delhi) cruisers were tagged to be converted into AA cruisers, with, first, single, then twin 4"/45s. That work seems to have been suspended when the war started. Navweaps says that, no matter how many 4"/45s were built, the Admiralty never had enough of them. The USN's supply of 5" guns was probably as tight. I have read about how the USN ramped up production of 4 and 5 inch guns during WWI, farming production out to a large number of companies, but never had enough to arm all the convoy ships, and escorts. I would expect the situation to have been the same in WWII.
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  2. As an exercise, I wondered what would have happened if the USN had started installing the twin 4"/50 that was experimented with in the late teens, as battleship secondary, instead of the 5"/51. Came up with mount weight and weight of fire numbers that made the 4" look like a good bet. From there, development into an analog of the British 4"/45 QF Mk XVI/twin Mk XIX mount would be a logical progression. If all the standards at Pearl had twin DP 4"/45s, in place of the 5"/51s, that would leave the entire upper deck, where the 5"/25s were historically, open for light AA.
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  3.  @TheJudge2017  I could guess, it was a matter of inertia. Having a long, heavy, barrel makes it harder to change the direction the barrel is pointing. I don't know if that is the case, specifically, with the 38, but I have read of other guns intended for AA use being cut down to improve their responsiveness.
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  4.  @gregorywright4918  yes, I am assuming a twin 4" mount, which the USN experimented with on a couple Clemsons. Looking at the photos of the mounts in use, the issue is clear. There was not enough deck room on the foc'se of a Clemson for the crew required to operate a twin mount. (all data taken from Navweaps) weight of a 5"/51 with single mount: 15.36-17.26mt. Weight of a twin 4"/50, guns and mount, 12.33mt. Rate of fire is the same, 8-9rpm, but adoption of a sliding breech, combined with the 4" fixed ammo could double that. Weight of the 5" common shell: 50lbs, vs 33 for the 4". Charge in common shell 5": 1.73lbs, 4": 1.39lbs. Range to penetrate 2" of armor 5": 8000yds, 4": 6300yds. So the twin 4" mount can fire more steel, with more charge than a single 5". Go to a sliding breech, and the twin 4" can fire a lot more steel and a lot more charge. Yes, the 5"/51 can penetrate more armor, but the DDs and torpedo boats that would usually be attacking are not armored. It would take a light cruiser to stand up to the 4". Yes, the 5"/51 has more range, 18,800yds @ 25 degrees, than the 4": 15,000yds @ 19.9 degrees, but torpedo boat armament was aimed by the Mk 1 eyeball, and, particularly hull mounted casements offered such a poor view of potential targets that maximum range is probably academic. I took my investigation one step farther: cutting the 4"/50 down to 45 calibers, and mounting them in a copy of the British Mk XIX mount. The result was lighter than the combination of a single 5"/51 and a single 5"/25, while being able to throw more steel than either of the 5" guns, and freeing the upper deck for more light AA armament. Yes, I am assuming the 1.1" for light AA, as that is what they had.
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