40mm Bofors or 1.1" ?

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maxs75
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40mm Bofors or 1.1" ?

Postby maxs75 » Fri Jan 21, 2011 6:38 pm

Hello,
It seems that during the second half of 1942 the production of 40mm Bofors guns didn't reach the desired level, an not all the ships (new building or refits) could be fitted with the 40mm Bofors.
For example the first three Fletchers were sent to South Pacific with 1.1" quad mount, and cruisers New Orleans and Minneapolis got two quad 40mm on fantail but retained 2 quad 1.1" as well.

I asked myself if the early escort carrier conversions were built with 1.1" instead of 40mm guns.
Friedman's US carrier design history says that
Early conversions had four quadruple 1.1" guns scheduled for replacement on a one-to-one basis by twin 40mm.
Late in 1942 however the 40mm envisaged for C3 were doubled, and those for the Sangamons increased to 9 twin 40mm guns.
About a year later the Sangamon battery was set at seven twins and 2 quads.


Now I'd like to know which ships actually carried the 1.1".
From photo at navsource.org, it seems that the following ships were completed with only 4 positions for quad 1.1" or twin Bofors.
In each case the positions were: two on the fantail and two on both sides of the fore flight deck.
ACV-9 Bogue
ACV-12 Copahee
ACV-16 Nassau
ACV-18 Altamaha
and the four Sangamons
Probably some or all of them could have the 1.1" fitted.
The question is: any info about that?
Copahee was commissioned first so she is the most probable one.

Card, Core and all ships commissioned in 1943 had 8 twins before going to combat. By that time the 40mm availability was better than in 1942. For that reason I guess that they all had Bofors as built.
The earlier Long Island and Charger probably never carried neither 1.1" nor Bofors.

Thank you in advance for any answer.
Max

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aurora
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Re: 40mm Bofors or 1.1" ?

Postby aurora » Sun Dec 14, 2014 5:17 pm

Due to labour shortages in Sweden-the United States Navy's Bureau of Ordnance purchased a twin-mount air-cooled example directly from Bofors, which arrived in New York on 28 August 1940. During that month another Dutch ship, the van Kinsbergen, demonstrated the Hazemeyer mount to Navy observers. The gun was quickly chosen as the Navy's standard anti-aircraft weapon, and the Navy secretly imported a set of imperial designs from England and started production illegally. A formal contract with Bofors followed in June 1941.

The resulting Mark 1 and Mark 2 weapons were intended for the left and right side of a twin mount, respectively, and were adapted by Chrysler for water cooling. After the war, the 3"/50 caliber gun Mark 27 mount began to replace the Bofors, because the "VT" proximity fuse would not fit a 40mm projectile.The Navy's satisfaction with the weapons was demonstrated by their practice of telegraphing Chrysler Corporation with the serial numbers of guns when they shot down an aircraft.
Quo Fata Vocant-Whither the Fates call

Jim

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Re: 40mm Bofors or 1.1" ?

Postby Garyt » Mon Jan 12, 2015 9:32 pm

Can't help you on which vessels carried the 1.1" weapons, Aurora.

But I do think the changeover was well worth it.

The Bofors had a better rate of fire, batter range, hit with a heavier shell so a better chance of destroying an aircraft.

It also did not seem to have many of the reliability and teething issues that plagued the 1.1".

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aurora
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Re: 40mm Bofors or 1.1" ?

Postby aurora » Tue Jan 13, 2015 10:36 am

This weapon was developed when an October 1928 Board convened by BuOrd decided that the 0.50" (12.7 mm) machine gun was too light a weapon for future air defense. Design began in March 1929 and initial testing with a single barrel weapon was conducted between March and May 1931. BuOrd decided to use these weapons in a quadruple mount as the combined rate of fire approached that of a single 0.50" (12.7 mm) MG of roughly 500 rounds per minute. It was felt that this rate of fire would result in a disabling amount of hits on even a fast-diving plane.

The projectiles for the 1.1" (28 mm) differed substantially from those for the 0.50" (12.7 mm) MG by having an explosive filler which was set off by a "super-quick" fuze. A 1934 report to the Navy General Board concluded that a single hit on any part of an aircraft would probably result in a forced landing.

This weapon was rushed into production as soon as it had passed its proving ground tests and was widely used on US warships before and during the first years of World War II. During early service use, it was found to be unreliable, prone to jamming and ineffective as an AA weapon. Never popular, they were rapidly replaced by the 20 mm Oerlikon and 40 mm Bofors AA weapons during World War II and by January 1945 they were in active service only on a few smaller ships.

All surviving guns and mountings were ordered scrapped in 1945 but some of the power drives were retained as being suitable for the twin Bofors mountings. In retrospect, it would appear that these defects were little more than teething problems and that the basic design was sound. However, this weapon still lacked the range and larger bursting charge of the 40 mm Bofors.

Construction was a monobloc barrel with chromium plating both internally and externally. Mod 1 had a threaded muzzle to accept a flash suppresser. Mark 2 was an experimental gas operated version that did not enter service.

The quad mountings were used with the Mark 44 Director, which was the USN's first off-mount director for automatic anti-aircraft weapons. This was a simple "dummy gun" type director and was manually trained and elevated. The Mark 44 contained optics and a spotting glass, but did not have any lead angle computing elements such as were found in later directors for automatic weapons such as the Mark 51.

The Mark 44 simply removed the operator away from the noise and smoke of the weapon, providing a clearer line of sight to the target. However, the Mark 44 did provide a basis for further development for the remote control of automatic weapons and greatly influenced the design of the Mark 51 and later small AA directors.

http://www.navweaps.com/Weapons/WNUS_1-1-75_mk1.htm
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Jim

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Re: 40mm Bofors or 1.1" ?

Postby Garyt » Tue Jan 13, 2015 7:21 pm

During early service use, it was found to be unreliable, prone to jamming and ineffective as an AA weapon.


Sometimes I think these writings about replaced weapons go a bit overboard on how terrible the original weapon was.

The 1.1" did shoot down a lot of planes the first two years of the war. The 40mm bofors was definitely better, and it was a good idea to replace with the better weapon, but "ineffective" seems to me to be a gross overstatement.

There were a fair amount of Japanese losses to AA fire at Coral Sea - and the 1.1" was in use on many vessels at that time.

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Re: 40mm Bofors or 1.1" ?

Postby Steve Crandell » Tue Jan 13, 2015 7:52 pm

Garyt wrote:
During early service use, it was found to be unreliable, prone to jamming and ineffective as an AA weapon.


Sometimes I think these writings about replaced weapons go a bit overboard on how terrible the original weapon was.

The 1.1" did shoot down a lot of planes the first two years of the war. The 40mm bofors was definitely better, and it was a good idea to replace with the better weapon, but "ineffective" seems to me to be a gross overstatement.

There were a fair amount of Japanese losses to AA fire at Coral Sea - and the 1.1" was in use on many vessels at that time.


Once the bugs were worked out it was fine, and some ships retained it for the duration of the war. The Bofors was a more powerful weapon, so of course it was used in most cases.

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Re: 40mm Bofors or 1.1" ?

Postby aurora » Tue Jan 13, 2015 8:06 pm

Quote Steve
"Once the bugs were worked out it was fine, and some ships retained it for the duration of the war. The Bofors was a more powerful weapon, so of course it was used in most cases".

All surviving guns and mountings were ordered scrapped in 1945; but some of the power drives were retained as being suitable for the twin Bofors mountings. In retrospect, it would appear that these defects were little more than teething problems and that the basic design was sound. However, this weapon still lacked the range and larger bursting charge of the 40 mm Bofors.
Quo Fata Vocant-Whither the Fates call

Jim

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Re: 40mm Bofors or 1.1" ?

Postby Garyt » Tue Jan 13, 2015 8:31 pm

Give me a Japanese 25mm, with a gyro stabilized sight, belt fed and water cooled over the Oerlikon 20mm or the 1.1" any day! :D

Throw in a more substantial mount that does not vibrate as much while you are at it too :think:

Dod Grile
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Re: 40mm Bofors or 1.1" ?

Postby Dod Grile » Tue Jan 13, 2015 9:13 pm

Some years ago I interviewed an old Asiatic Fleet vet (a GM3c) who survived the Java Campaign & was then sent to smaller ships, sub-chasers and such...On one vessel later--I don't recall which--he worked w/the 1.1" weapon again. This after having been around the earlier variation in the Asiatic Fleet...which indeed gave considerable trouble. According to him it was a sound weapon, but needed more maintenance & care than they were able to give it in the NEI, and I was a little surprised to hear that from him. But, he was quite unequivocal about it. (I would consult the notes I took of our talk, but too much trouble right now...Something about a lighter grade lubricating oil being important, I remember.) However, I do not believe for an instant it would have ever been preferred over the 40mm Bofors.

Additionally, while the MK44 director was associated w/the 1.1" it did not make it to all ships; e.g., HOUSTON had no directors for her four 1.1" quads at all. Nor did she have jigs to keep them from shooting into the ship on extreme bearings, but one of her officers devised this (ad hoc) during the campaign.


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