Naval Gun Projects

RP1

RP1

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I have various images of naval gun projects. I'll add them here as I scan them. Unless here is moved to a somewhere else. :)

RP1
 
First up, a 35mm CIWS proposal presented at the 1991 US Navy League show.

35mm_ciws_1991_1.png


Source: Navy International, October 1991, Vol 96, No 11, Publ: Maritime World Limited

EDIT
Some information from the same source:

• GD proposal to use GE Cased Telescoped ORDALT 35mm weapon system.
• 8 barrels.
• 8000rpm.
• Balanced linkless feed holding 1200 APDS rounds.
• Nearly 6x on target energy per shot compared with 20mm Phalanx.
• Dispersion of less than 1mrad.
• MV greater than 1130m/s.

[Edit: corrected date]
 
Last edited:
Cool! ;D ::)

More! GIMMEE MORE! (Was that over the top? I can never tell. <G> )

Bigger guns, MORE POWER!
 
RP1 said:
First up, a 35mm CIWS proposal presented at the 1991 US Navy League show.

35mm_ciws_1991_1.png


Source: Navy International, November 1991, Vol 96, No 11, Publ: Maritime World Limited
Click to expand...

That would be a beast. :eek:
 
How many barrels did the gun have??

It looks like they stuffed a tree trunk in there!!

Any idea of it's performance specs??
 
Next, Myriad:

25mm_ciws_1991_1.png


Sources:
Navy International, November 1991, Vol 96, No 11, Publ: Maritime World Limited
Friedman, N, "The Naval Institute Guide to World Naval Weapons Systems 1997-1998", Naval Institute Press, Annapolis, Maryland

• Joint venture between Breda, Contraves, Elsag and Selenia.
• BARRAGE gun mount has 2 25mm 7 barrel KBD Gatling guns on a canted platform, to reach the zenith.
• 10,000rpm.
• MV. 1270m/s.
• Each gun plus 1000 rounds is 1600kg.
• Each BARRAGE mount is 7700kg with 2000 rounds (4 boxes of 500).
• Balanced linkless feed system with 2 ammo boxes per gun, so they can switch between KBB AMDS and APFDS-T.
• Patented "hangfire" detection mechanism.
• Similar to Sea Zenith and AK-630 in that it uses separate directors, surveillance radars and gun mounts.
• Several directors and guns can be tied into a common bus, using standard MAGICS consoles.

I remember this weapon appearing a later issue of Janes. There were some issues regarding the rigidity of the mount. Similar problems had been discovered by the RN when trialling the Sea Zenith system. [Friedman] This implies that the quoted dispersion may have been optimistic.
 
Now, the Kashtan CIWS will deliver 10000rpm too , but a muzzle velocity of 1270m/s is incredible ;D
 
More Myriad. This system seems to have got around a lot.

25mm_ciws_1989_1.jpg


Mock-up presented at the Italian industry expo Mostra Navale, May 1989.

Source:
International Defense Review, 7/1989

-RP1
 
And now for something completely different...

27mm_ciws_1990_1.jpg


Model shown at Defendory International Exhibition, Athens, Greece, 1990

• Diehl group
• "Third Generation CIWS"
• Primarily against sea-skimmers
• 4 27mm Mauser guns, combined ROF of 7200 RPM
• APFSDS ammunition
• Mount 3500kg including 1440 rounds
• No deck penetration
• Trials were expected from mid-1991 on a German FPB

And no, I can't quite figure it out either. I think the entire mount shown in the picture traverses, like crew-served 20 and 30mm guns.

Source:
International Defense Review 11/1990

-RP1
 
Looks like something out of Star wars, quite frankly.
I wonder how it comes that with so many advanced concepts the " Vulcan" CIWS is still the industry standard in the West.
 
One possible issue is dispersion when one of the guns of a multi-gun system jams or otherwise fails. I had read (can't remember the source but I'll track it down) that this issue had arisen with the Contraves Seaguard/Sea Zenith system when in went into service on Meko 200's sold to Turkey (I think).

The other may be size and complexity, hence cost. The more guns, the more ammo feeds and the bigger it gets with more things that can go wrong and so on. I think readers on this board will recognize the vicious circle that this will lead to.

Anyway, those are my thoughts on the issue.

8)
 
"Vulcan" CIWS is still the industry standard in the West
Click to expand...

It's not that much of a standard:

• US CIWS = Phalanx
• UK CIWS = Goalkeeper (Based on trials of Phalanx, Goalkeeper, Sea Zenith and Meroka). Phalanx used for retrofits due to smallest ship impact.
• Dutch CIWS = Goalkeeper
• Italian CIWS = 40mm / 76mm guns
• Spanish CIWS = Meroka
• French CIWS = None, Mistral (?) ILMS instead

There is a lot to be said for "getting there first". That combined with a very large order (The USN) reducing unit cost, and a relatively small footprint (especialy when compared to Sea Zenith) made Phalanx very attractive for smaller navies wishing to include a CIWS in a design which in many cases was not designed specifically for it.

- RP1

PS: Regarding the dispersion issue with Sea Zenith, my notes from Friedman (1) are below:

Guns to close together lead to interference, vibration due to open flexible mount, jamming can occur during long engagements

(1) Friedman, N, "The Naval Institute Guide to World Naval Weapons Systems 1997-1998", Naval Institute Press, Annapolis, Maryland

 
I have seen references in Admiralty documents dating from 1948 to an anti-aircraft and anti-missile system called "DACR" - Direct Acting, Close Range apparently. I've tried chasing it up, but all I could find was that it MAY have been a sextuple Bofors L70 on a Mk.12 mounting or a quad Vickers D.10. The mounting was also refered to as Scarecrow V.

Sounds like a variation on the "Antlered Beast" officially called STAAG - Stabilized Tachiometric Annti-Aircraft Gun.

Perhaps some-one with more naval material could shed light on DACR. It has bugged me for years.

KB
 
It has bugged me for years
Click to expand...

You and me both. IIRC not even Anthony Williams can find anything about it. I think he described it as a "Sextuple 40mm Bofors on a Scarecrow mount".

Given that it was to be fitted to the never-built cruisers, which had 6 and 3 inch rapid fire radar-directed AA guns, I suspect it was somewhat simpler than the STAAG, and was intended for last-ditch blasting at aircraft coming straight at the ship. The "Direct Acting" implies that in my mind.

RP1
 
I seem to remember a 32mm Oerlikon being involved, but that was about it. 32mm was such an odd calibre (like the 42mm RED QUEEN) it was probably too bizarre for the Admiralty.

Thanks

KB
 
This might be a further development of the 4*27mm Mauser mount shown above:

"MIDAS (or AMS-4-27, later Drakon) consists of a Vierlings arrangement of the outstanding BK-27 airplane mounted gun on a modified 40mm Bofors carriage and reaches a cadence of with 1.800 RPM per pipe, thus 7,200 RPM altogether. MIDAS uses for weight reasons only a Signaal target illumination system, the raw target datas come from the ship sensors. The range is 3.000m. Equipment with two additional IR-guided Stinger air defense missiles was originally intended. Developed to become the standard CIWS of the Federal German Navy for its FACs, mine countermeasures units, tenders and frigates but was dropped after the end of the cold war for cost reasons. Renamed Drakon for international marketing. MIDAS fires wing-stabilized APFDS darts with very higher kinetic energy. The BK-27 and the ammunition were probably convincing enough, because as the German Navy chose the single recoilless 27mm gun mount (MLG-27) as replacment for all its 40mm Bofors and 20mm Rh-202 guns."

Drakon.jpg
 
I found this on Globalsecurity.org

mg-1-s.jpg


MDG-351 35-mm Millennium Gun

In March 2002 Lockheed Martin, Akron, Ohio, and Oerlikon Contraves, Zurich, Switzerland, joined forces to produce and market the rapid-fire Millennium Gun. The Millennium Gun is the only multi-mission close-in weapon system capable of engaging fast-attack surface craft and near-shore land targets in littoral and riverine waters, as well as defending against anti-ship missiles and aircraft in all environments.

The gun's highly effective inner layer defense capability extends ship self-protection to ranges greater than any other close-in weapon systems. Creating a "wall of steel," the Millennium Gun fires 35-mm ammunition, including the advanced Ahead round, at 1,000 rounds per minute. Each Ahead round dispenses 152 subprojectiles that form a cone-shaped pattern. The subprojectiles destroy a target's control surfaces, seeker and other vital components as it moves through the wall of steel.

The Millennium Gun is a low-cost, unmanned, remotely controlled gun mount. It is compatible with all modern and legacy sensors and fire control systems. It fits on a number of ship classes, including such advanced designs as the U.S. Coast Guard National Security Cutter and the Littoral Combat Ship. Oerlikon Contraves has received expressions of interest from several navies for mounts on frigates and corvettes.

The Millennium Gun will give navies a multimission-capable deck gun, defending against sea-skimming cruise missiles and other air threats in the open ocean and against the asymmetric threat of small surface craft in littoral and riverine waters.

The gun's kill radius varies according to the type of threat it engages. Testing has shown it to be lethal against aircraft and helicopters at 3.5 km, against cruise missiles at 2 km, and against anti-ship sea-skimming missiles at 1.5 km. These distances extend the close-in defensive perimeter and the time available for a ship to engage and destroy an imminent threat

The Millennium Gun's versatility and modularity was demonstrated during the U.S. Navy's Fleet Battle Experiment-Juliet, scheduled for July and August 2002. Lockheed Martin's Sea SLICE, an advanced technology demonstrator vessel participating in the exercise, was fitted with the Millennium Gun on its bow. The exercise highlighted the gun's adaptability to fit on a number of ship classes. Its low weight, small footprint and easy loading of ammunition make it ideal for new ship construction and existing ships earmarked for modernization.
Click to expand...

Is this one operational?
 
It sure is. It was bought by Denmark and will be installed on the Absalam class and on the new Patrol Ship.

Regards
 
more naval material could shed light on DACR
Click to expand...
I'm not sure it will!
There is a long and authoritative article "Post war cruiser designs for the Royal Navy `1946-1956" by George Moore in Warship 2006 (pp38 - 58). The background to the changes in design is money, and the changes from gun to missile armament. DACR gets several mentions, the last of which (a table of 1951/52 cruiser designs some with 6" and 3", some with 5", but all with 4 DACR) has a footnote:
DACR: Direct Acting Close Range - probably cancelled sextuple Bofors L70
No details, and none of anything other than the Bofors. George Moore is pretty thorough, and gives his ADM and DNC dept Work Book sources, and his article traces well the progress, or lack of it, with the larger calibre AA weapons of the period - 6", 3", and 5".
The sextuple Bofors L60 was mounted on HMS Vanguard, twins and singles elsewhere. The navy considered the L70 (which the army adopted rather than Red Queen) to replace their L60s but did not adopt it.
The impression I get from the first mention of DACR is that it was an acronym for a requirement for the post war cruisers, to supplement their 6" and 3" guns, rather than a particular design of weapon system. That requirement that might be most easily met by the sextuple L70 expected (in 1948) to enter service in 1957. Given the long lead time from 1948 to 1960ish before the relevant cruiser designs might be built, it could well have been a "see what turns up" approach, such weapon developments being very fluid at the time, but probably with a timescale hoped to be a little shorter. There are (good?) naval precedents for this approach. The Vickers 2pdr pompom was included in the armament of the cancelled 1921 G3 battlecruisers (with 6 or 10 barrels), although the County cruisers of 1927 had to wait 3 years for their definitive 8 barrelled version, fitting single barrelled guns in the meantime, and destroyers until the late 30s for their quad. A more recent equivalent to DACR would perhaps be the rush to mount Phalanx after the Falklands war.
 
Hello, I got some more detailed info about Myriad directly from Oto Melara.

1 Myriad CIWS
1.1 History and development background
To meet the threat from the next generation of high-speed manoeuvring anti-ship missiles, Oerlikon began to examine a Gatling principle gun and in 1984 developed a six-barrel prototype.
The company continued this work and in 1988, developed the seven barrel KBD 5000 (later Breda-Oerlikon KBD or Barrage) which was selected by an Italian consortium as the basis for a new CIWS system, Myriad.
This system was revealed at Mostra Navale in May 1989 when a mock-up of the system was displayed.
1.2 Technical description
The purpose of the Myriad system is to predict the area which a missile or missiles had to travel, saturating that area with projectiles in order to ensure the destruction of the target.
These objectives is met by means of a system which used twin 25 mm calibre Gatling-type guns capable of firing more than 10000 rds/min using an ammunition designed to penetrate even armoured missiles.
Each barrel is at 20° angle to the cradle’s axis, positive for the right hand and negative for the left-hand. This compensates for shell drift when each barrel rotates. They are supported by a dual-band, acquisition and tracking radar displaying data to a high resolution display system.
The gun is the Oto Melara Barrage Twin Gatling Naval Mounting, a new generation CIWS that fully satisfies the following requirements :
• extremely high rate of fire: 10.000 rounds /min.;
• high dynamic characteristics ;
• complete automation;
• plentiful availability of rounds ready to fire (2000);
• dual feeding system;
• high reliability and ease of maintenance;
• capability of operation in NBC conditions;
moreover
• the design of ammo loading system allows reloading from a protected environment (below deck);
• favourable centre of gravity position, by virtue of a proper mass distribution, ensuring high firing accuracy.
The characteristics of the mounting together with an appropriate Fire Control System make the system particularly suitable for operation against the following targets:
• all types of the present generation "Sea Skimming missiles";
• "Sea Skimming Missiles" of the new generation (with particular regard to those highly manoeuvring at both subsonic and supersonic speed);
• ARM missiles;
• high and very high diver missiles;
• anti ship bombs (gliding, laser guided, etc.);
• low level attack aircraft.
The gun rotates at 12 rps and is capable of firing up to 5000 rds/min. It is controlled by a microprocessor and features an elevation compensator to adjust the feed so that it remains parallel to the barrel.
Firing takes place when barrel rotation has reached a steady speed in order to avoid dispersion, with the fire control system programming the burst length. The software allows for a 0.5 second interval before the fire command. This interval has no effect upon reaction times because the ballistic solution allows for it.
Click to expand...
 
more...

1.2.1.3 Automatic Feeding System.
The automatic feeding system consists of, for each cannon :
• 2 Ammunition Magazines,
• 2 Ammunition Conveyors (Front and Rear),
• 1 Ammunition Exchanger,
• 1 Cannon Conveyor,
• 1 Elevation Compensator,
• 1 Empty Cases Box,
• 1 Channel for Empty Cases.
1.2.1.3.1 Ammunition Magazines.
Each magazine is completely independent one of the other.
The automatic link-less magazine consists of a box with a vertical fan fold of special transfer roller chain provided with round carriers; the paths into which the chain slides are milled into the box walls.
The chain is moved by a hydraulic servo motor controlled by a digital servo valve through a reduction gear.
The automatic Ammunition Magazine and the relevant conveyor transfer rounds to the exchanger.
1.2.1.3.2 Ammunition Magazine Conveyor ( Front and Rear).
The conveyor consists of a closed loop special transfer chain, different from that of the magazine and a supporting structure which guides the chain to the exchanger.
The conveyor feeds live rounds to the exchanger.
Each magazine, front and rear, is connected from a feeding point of view to the Ammunition Exchanger via its conveyor.
At the bottom , each conveyor is provided with a transfer station that receives rounds from the ammunition magazine chain and transfers them to the conveyor cup chain.
1.2.1.3.3 Ammunition Exchanger.
The Ammunition Exchanger gives the possibility to feed the Cannon Conveyor either with the front or the rear magazine.
This gives a high survivability of the feeding system and also permits having two different types of round ready to fire in the two magazines when required.
The Exchanger is composed of :
• a supporting structure,
• 3 shafts with three couples of starwheels,
• 2 claw clutches hydraulically operated (for the Ammo Magazine selection),
• 3 deviators to determine the feed path inside the Exchanger in consequence of the selection actuated,
• the relevant solenoid operated valves and tubing.
1.2.1.3.4 Cannon Conveyor.
The Cannon Conveyor consists of a closed loop special chain very similar to the one employed for the Ammunition Conveyor.
This chain passes through the Elevation Compensator and transfers the live rounds to the Cannon Transfer Station and the empty cases to the empty case duct.
1.2.1.3.5 Elevation Compensator.
The Elevation Compensator is a two ways twistable duct composed of plates packed together by means of a central shaft and connected to each other by means of extendible rubber cords.
It is fixed on one side to the cradle and to the Exchanger structure on the other one.
In the plates are present the guides for the chain of the Cannon Conveyor.
The Elevation Compensator allows the feeding of the cannon at any elevation.
1.2.1.3.6 Empty Cases Box.
The Empty Cases Box is fixed to the basket structure by means of quick release fasteners and collects the empty cases through the duct from the Ammunition Exchanger.
It can be removed quickly from its position.
Click to expand...
 
more...

1.3 Ammunition
The cannon can fire all the ammunition of the OERLIKON 25 mm KBB Family.
1.3.1 Anti aircraft ammunition
Ammunition with identical external ballistic characteristics (muzzle velocity 1160 m/sec.) :
• T.P. training practice round;
• T.P.T. training practice round with tracer;
• H.E.I. high explosive incendiary round (with base fuse).
1.3.2 Anti missile ammunition
Ammunition with identical external ballistic characteristics ( muzzle velocity 1200 m/sec.) :
• A.P.P.-T - ARMOUR PIERCING DISCARDING SABOT WITH TRACER (SHORT TRAJECTORY);
• A.P.D.S.-T. - ARMOUR PIERCING DISCARDING SABOT ROUND WITH TRACER;
• A.M.D.S.- ANTI MISSILE DISCARDING SABOT ROUND;
• F.A.P.D.S. - FRANGIBLE ARMOUR PIERCING DISCARDING SABOT
1.3.3 Auxiliary ammunition
• BREAK-UP round.
1.4 Future project
The project has been closed, in spite of its capability, because of a change of defence philosophy against new missiles, which are characterized by high manoeuvrability.
Today, the tendency is to engage the target at greater range, avoiding the saturation of an area too close to the ship and any resulting collateral damage.
Also the un-success of 25 KBB played a very important role.
In order to obtain a sufficient kill probability, at reasonable hand-off form the ship, the new tendency is to make an effort in investigate new generation guided ammunition, surely of bigger calibre, (see 3.4.1 - HE - DART), capable to destroy the target with a little number of rounds and at a greater range.
Click to expand...
 
From RINA's "The Naval Architect" November 1983, review of RNEE 1983:

• Vickers "Sea Dragon" CIWS.
• GAU-8A based system
• Project started in 1972, but not publicly announced until 1982
• Ericsson Giraffe C-band radar for detection (separate unit)
• On-mount tracking radar same as in the LWSW proposals - Marconi set (VFM-30?)
• Ferranti processing equipment
• Jokingly suggested that system designator of "GBG-30" means "Great British Gun"
• Mounting similar to Goalkeeper, without E/O and surveillance radars, and with slightly larger FCR

-RP1
 
That's going to leave a mark. Jane's has featured articles on this development recently. The "departure" of such a projectile at full size would be pretty spectacular - one idea is to disperse the huge amount of energy stored in the rails by allowing it to arc into the air.

RP1
 
RP1 said:
That's going to leave a mark. Jane's has featured articles on this development recently. The "departure" of such a projectile at full size would be pretty spectacular - one idea is to disperse the huge amount of energy stored in the rails by allowing it to arc into the air.

RP1
Click to expand...
I would LOVE to see that. From half a klick away...
And for some reason I think it would play merry hell with a lot of electronics.
 
I'm not sure if it was here or on another forum, but I remember a discussion of a Rarden based remote control mounting proposed for the RN. Thanks to an old issue of the gleefully entitled "War Machine" (The 1980's, eh?) I have a few details.

"LS30R"
• Laurence Scott Defence Systems mounting
• RARDE 30mm Rarden automatic cannon
• Power driven and LOS stabilised
• Tests carried out by RN at sea on trials FF HMS Londonderry and on land at the Fraser Gunnery Range
• Hit a 2m2 target 80% of the time at ranges between 1000-1300m
• HE, APSE and APDS rounds
• LS30R was to replace 20mm and 40mm weapons, initially starting on OPVs
• Basic mounting can be used with 30mm Oerlikon KCB and Mauser Model F (LS30B and LS30F)
• -20 to +70 degrees elevation
• 6-22 rounds on-mount

This was the weapon DJ Brown used on a lot of his independent concept designs.

EDIT 2011-07-26:

Warship #25 has an article by Antony Preston entitled "The Naval Rarden Gun" with pictures and a description of the development process. Obviously I'm not going to reproduce the whole thing here, but a few points:

• The mounting was a private venture development of the Laurence Scott / Electromotors Optical Fire Director mounting. As a secondary role, the mounting could act as a director for another system.
• The mounting was tested with Oerlikon 20mm and Rarden 30mm.
• Aim-off and range were estimated manually by the operator. A predictor was to be available for later versions, but no mention is made of a rangefinder, so would still have been based on estimated ranges.
• Numerical specifications are provided. As a summary the complete mounting was 800kg in mass with 2m overall height and a swept radius of 2.2m. Elevation limits were -20/+70 degrees.

- RP1
 
I´ve been trying to trace these guns, without luck:

480/L45 -the Japanese supposedly built and trialled such a weapon in 1916
127 British, planned in the 1950´s (not built I think)
137 Planned by USN during WWII, built?
35 Planned by USN late WWII (probably not built)

Does anybody here know anything or have drawings/pictures/data of any of these?
 
RP1 said:
I'm not sure if it was here or on another forum, but I remember a discussion of a Rarden based remote control mounting proposed for the RN. Thanks to an old issue of the gleefully entitled "War Machine" (The 1980's, eh?) I have a few details.

"LS30R"
• Laurence Scott Defence Systems mounting
• RARDE 30mm Rarden automatic cannon
• Power driven and LOS stabilised
• Tests carried out by RN at sea on trials FF HMS Londonderry and on land at the Fraser Gunnery Range
• Hit a 2m2 target 80% of the time at ranges between 1000-1300m
• HE, APSE and APDS rounds
• LS30R was to replace 20mm and 40mm weapons, initially starting on OPVs
• Basic mounting can be used with 30mm Oerlikon KCB and Mauser Model F (LS30B and LS30F)
• -20 to +70 degrees elevation
• 6-22 rounds on-mount

This was the weapon DJ Brown used on a lot of his independent concept designs.

- RP1
Click to expand...

Hm came accross this forum just generally browsing through google on some related stuff and this came up, cant add much to most of your discussions but I can certainly shed some light on this. The LS30R died literally dead no more it never went past the prototype. However no before it spawned a son the LS30B this then changed its name by deed poll to the DS30B just prior to entering service with the RN. Mainly down to a company name change as laurence Scott Defence systems is now MSI-Defence Systems ltd www.msi-dsl.com.

The DS30B has been around for 20 years now inservice with several navies. It now has a replacement the SEAHAWK linkage here

http://www.janes.com/events/exhibitions/dsei2007/sections/daily/day3/seahawk-family-nests-at-d.shtml

http://bp0.blogger.com/_JEyyV88-wp8/RxKRxzDBkrI/AAAAAAAAAK0/4qCrw8QIDmo/s400/ascg.JPG

The new Seahawk system has already undergone succesful trials onboard RN vessels as the ASCG, HMS Somerset has mentioned the trials in his Blog about halfway down.. He calls it the bushmaster.

http://hms-somerset-co.blogspot.com/search?updated-max=2007-10-22T07%3A09%3A00Z&max-results=7

Spec
 
Kugelblitz,

I seem to recall seeing a number of late WWII USN drawings with 37mm marked on them for the light AA guns. IIRC, the idea was floated to replace the 20mm Oerlikon with a derivative of the M9 37mm cannon used on PT boats, which was itself taken from the P-39 Aerocobra. Hope this helps.
 
I went through the USN gunnery syllabus in the mid-50s. IIRC, we were told that befor the end of WWII, Kamikaze attacks changed the philosophy os USN anti-aircraft gunnery. Against this type of attack, 20 mm and even 40mm were useless, what was required was a shell with sufficient kinetic energy to deflect the aircraft from a collision trajectory. For this reason, the 3"/50 dual mount was rushed into production to replace quad 40mm mounts (we were told it was essentially a drop-in replacement). I had the good fortune to train and live fire on a 40mm quad (first loader), 3"/50 (first loader), 5"/38 (second loader) and powder handler for the 16" main battery on an Iowa class ship which when I was on it was essentially in WWII trim (except all 20 mm mounts had been deleted).

Of course, that philosopy has since been revised several times, currently with the small caliber extremely high fire rate guns which are designed to defeat the threat with multiple high velocity strikes.

Best Regards,

Artie Bob
 
Interesting. I recall reading (probably Friedman, but I'm not sure) that the move from 40mm to 3" was driven by the inability to manufacture a VT fuze capable of fitting in a projectile smaller than 3". The "plan" was to replace the quad 40s with the 3"/70 twin automatic mount on a 1-for-1 basis with the 3"/50 twin as a stand in until the development of the 3"/70 was completed. In fact the 3"/70 had a tortured development and only went to sea in about 8 ships. The progress in AA missile technology was a beter invenstment and the 3"/50 was seen as good enough.

Cheers
 
On principles:
Deflecting a 10000lb aircraft+bomb travelling at 400ft/sec using a 2lb (40mm) or even a 15lb (3in) shot travelling at 2000ft/sec is a no-go. The 2lb shell has only 1/1000 of the momentum of the plane.
You need either a lucky hit on a control surface to do the deflection, or an explosive shell whose fragments disrupt the aircraft structure. Hence use a larger calibre, with a heavier shell. But the gun is slower-firing, and you need to get damage from near-misses, so no medium calibre AA is much use until the VT fuze ensures a near miss will detonate close enough for many shell fragments to hit the 'plane.
The aim is to blow the attacker apart sufficiently far away, not just to knock it off course. The 3in fires a shell 7 or eight times as heavy as the 40mm, and fires fast enough to put several times the weight of shell in the air compared to the good old 5in - especially if the comparison is with 90rpm L70 3in, though they took until well after the war had ended to get working. Modern small calibre guns are very rapid firing, fast enough to get many hits and so disrupt the structure.
The British 3in L/70 on HMS Tiger eventually worked quite well. The UK post-war rapid fire 5in never saw service. The objective was 70-90 rpm. The RN never got anything, but the army got a prototype Green Mace, which is in the Firepower Royal Artillery museum at Woolwich Arsenal. An awesome beast:
http://www.skomer.u-net.com/projects/greenmace.htm
 
It should be noted that another kill method is for (small), energetic projectiles or fragments to cause deflagration / detonation of the warhead or rocket motors / fuel tanks.

RP1
 

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