1. #1
    As far as I have discerned by reading various posts on this forum, US aircraft carriers during the war in the Pacific carried 20mm, 40mm, and 5-inch AA guns.

    Why those calibers? 20mm being the smallest, wouldn't those still be hard to aim when firing at an aircraft at close range? Would not twin .50 cal or even quad .50 cal mounts have been more effective at close ranges? Especially considering the weakness of Japanese aircraft to .50 cal, often lacking armor plate or self-sealing fuel tanks?

    How were these weapons arranged on the ship?

    Were the aircraft carriers of other nations similarly armed? If not, how were they?

    Are there any websites related to this topic that may be of assistance?

    - Lat
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  2. #2
    As far as I have discerned by reading various posts on this forum, US aircraft carriers during the war in the Pacific carried 20mm, 40mm, and 5-inch AA guns.

    Why those calibers? 20mm being the smallest, wouldn't those still be hard to aim when firing at an aircraft at close range? Would not twin .50 cal or even quad .50 cal mounts have been more effective at close ranges? Especially considering the weakness of Japanese aircraft to .50 cal, often lacking armor plate or self-sealing fuel tanks?

    How were these weapons arranged on the ship?

    Were the aircraft carriers of other nations similarly armed? If not, how were they?

    Are there any websites related to this topic that may be of assistance?

    - Lat
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  3. #3
    Tater-SW-'s Avatar Senior Member
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    Early war USN CVs also had a large number of MG mounts. The reason for 20mm over cal .30 or .50 weapons was most likely hitting power. You'd just assume that if you get a stray hit, it does the most damage possible, particularly from the front where the engine is.

    The other issue is range. .50s have pretty decent range, but I'm unsure of theri stopping power vs aircraft at extreme ranges. At low alt the planes you are dealing with are torpedo planes, once they are inside 1000 yards you are in serious trouble, the idea is to kill them, or foil their aim before they get close enough to drop. High alt cons are dive or level/glide bombers. Same thing applies, by the time they are in the effective range of .50 cals, it is probably too late to prevent them from taking an aimed shot.

    Later in the war, kamikazes were an issue, in which case the only thing that mattered was utterly destroying the target.

    tater
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  4. #4
    U.S. carriers started the war with .50-cal machine guns and the 1.1-inch (about 28mm).

    Japanese has .50 cals and a 25 mm.

    The .50 cal didn't have enough range and the 1.1 was simply horrible, prone to overheating, misfires and all other sorts of problems.

    The purpose of an AA gun is not just to shoot a plane down, but to shoot it down or at least to distrupt it's approach before it drops its ordinance. Fat lot of good that shooting down a torpedo bomber will do, for instance, if it's torpedo is already in the water and headed to your ship to sink it.

    So the .50 cal was no good. It could tear planes up after they zoomed over at masthead height, but by then it was too late.

    The 40 mm Bofers was a license-produced Swedish design. It was so good, Germany license-produced it during the war too. It was highly reliable, had a great rate of fire, a good fire control system and it's two-pound explosive shell was quite lethal. Great weapon.

    The 20 mm, another license-built design from some European neutal nation, had a huge advantage -- you could put one anywhere. It was relatively lightweight so you could stick one on just about any open space on deck without creating weight or top-heaviness problems.

    The 20 mm was the last line of defense. It took a horrible toll on low-flying torpedo bombers and on dive bombers as the pulled out of their dives.

    The 5" 38-cal (5-inch bore, 38 "calibers" long, or 38*5" = almost 16 feet) was picked because it was one of the biggest gun you could use for AA that still had some anti-ship punch. (Both the British and the Japanese experimented with 8" dual-purpose guns on their cruisers, but neither country could develop a version that really worked.) The 5-38 was a pretty good AA gun that got a lot better when the U.S. discovered they could increase the velocity of the shell by trimming off some of the rear edge of the shell to streamline the projectile, when it was hooked up to excellent, radar-guided fire control systems and, finally, when the proximity fuse was invented. The smallest gun that could use a 1940s proximity fuse would be a 3-inch.

    The Japanese 25 mm was good enough early in the war, but had a slow rate of fire, as I recall. The big problem, though, was a widening technological gap that really started in 1942. American fire control, including automated systems, keep getting better while the Japaneses pace of improvement didn't.

    The real turning point was the battle of Santa Cruz. The Japanese and Americans were roughly equal, at least, before that point. This was the Enterprise's first battle after a refit and repair that added tons of 20mm and 40mm guns to her.

    The Japanese "won," but lost so many planes that they carriers might as well have been sunk too. They had nothing left, allowed the damaged Enterprise to ferry planes to Guadacanal after the battle, which is all that kept the island from falling.


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    [This message was edited by Doug_Thompson on Wed August 04 2004 at 02:34 PM.]
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  5. #5
    Latico's Avatar Senior Member
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    The 5 inch gun turrets for and aft of the island on the US CV's were removed and replaced with quad 40mm Bofars soon after the war began. As the war continued, the armament was constantly upgraded each time one went in for repairs or overhauls. I don't think the Essex Class CV's ever had the 5" guns.

    The DD's and DE's that escorted the CV's had plenty of the 5" AAA though.
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  6. #6
    Tater-SW-'s Avatar Senior Member
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    The Essex class CVs had 4 5/38 guns in dual mounts, fore and aft of the island. There may have been other 5 inch guns as well.


    BTW, this is the new Yorktown, CV 10.


    tater
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  7. #7
    The Essex Class CV's carried their dual 5" 38 cal mounts till the fleet modernizations in the 50's and 60's. Bunkerhill still had hers when she went to the knackers in the late 60's.

    With the VT (proximity) fuse and the excellent MK 37 director system the 5" 38 remained the premier Naval AAA weapon throught the war.

    The Orlikon 20 mm canon (Swiss design) was an excellent close in weapon, but did not have the range to STOP a Kamakaze if it got past the 40mm Bofors. The rattle of the 20's signaled that it was about time to "hit the deck".
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  8. #8
    You got some of it right, Latico. The Lexington and Saratoga had twin 8" turrents, just like cruisers. The Sara's were removed shortly after the war broke out and were replaced by 5", I think. I'm pretty sure the Lex took her cruiser guns down with her.


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  9. #9
    Do a google search for "Helena proximity fuse." Some good reading. I remember reading an account from someone stationed below decks on a CV during WWII and as Fliger747 said he recounted when you heard the 5 inchers open up you new something was going on. Then when you heard the 40's go you got a little more concerned and when the 20's kicked in you became very worried.
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  10. #10
    Latico's Avatar Senior Member
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    <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Doug_Thompson:
    You got some of it right, Latico. The Lexington and Saratoga had twin 8" turrents, just like cruisers. The Sara's were removed shortly after the war broke out and were replaced by 5", I think. I'm pretty sure the Lex took her cruiser guns down with her.

    http://www.model-news.com/projekt/335col/baerlog.jpg
    _Proud Charter Member of the Do-Do Birds Luftwhiners Chorus_<HR></BLOCKQUOTE>

    The 8" turrets were removed from the Lex, too, probably replaced with the 5/38's. This was done during repairs at Pearl after the first time she was torpedoed.

    I think the 8" gun turrets removed from both the Lex and Sara were used as coastal shore batteries around Oahu.
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