Direct Acting, Close Range (1950's 34mm CIWS)


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From British Secret Projects: Hypersonics, Ramjets and Missiles.

'Interestingly, Popsey was in competition(in the 1950's) with a gun-based system called Direct Acting, Close Range (DACR in current parlance, a CIWS) as the main defence for small ships. The gun-based proposal comprised a sextet of Oerlikon 34mm cannon in a Scarecrow V mount.'

Has anyone heard how heavy this was planned to be?
The sextuple Bofors 40mm weighed just over 21tons.
See also,1672.0.html
Bottom of first page and then later.
What the 34mm Oerlikon is/was I don't know, but KB probably found some refs at TNA.
I'd like to see more details of the 34mm. O. went in for odd calibres - eg 42mm Red Queen
Sorry to disinter such an old thread, but I'd be interested to hear if anyone has any more info on DACR.

This seems to have been a role rather than a specific gun (as CIWS is now) with various different guns (in different calibres) and mountings proposed to meet it. It seems to be difficult to find out which gun mountings were considered, though.

I doubt that the 34mm had anything to do with Oerlikon. There was a Swiss AA gun in 34mm calibre, the FMK 38 which was in service from 1938 to 1968, but it wasn't an Oerlikon design. I have a drawing of a 34mm round of ammunition for a Vickers Class T gun, which has a longer cartridge case than the Swiss one, but no other info about it.
Tony Williams said:
Sorry to disinter such an old thread, but I'd be interested to hear if anyone has any more info on DACR.

In the Notes of Norman Friedman's British Cruisers (Chapter 11, Note 2) it is stated that In Jan 52 DACR was code-named Zenith. There were four possibilities: D.10 (30 tons), Scarecrow (39 tons), V.A. Crow T (36 tons) and Marquardt (27 tons). Each design included 11.75 tons of ammo.

For the third possibility, V.A. might be Vickers-Armstrong, and the T in the name might refer to the Class T gun you mention.

The last, Marquardt, is a puzzler. The only industrial firm that makes sense is the US Marquardt Aircraft, but they seems to be solely ramjet people. Perhaps there was a designer with that surname at a gun company? The surname is German, so it's not a stretch to posit a Swiss designer with that name.
Could the Marquardt in question be Frank Marquardt?
Frank Marquardt, while working for the Navy in the late 1960's, spent
considerable time trying to promote redesign of the 20 mm steel case to take
advantage of the strength of steel by building thin-wall steel cases and
increasing chamber volume by 10% to 15%. This idea was revived in the late
1970's on the GAU-8. It was reasoned that steel could be made three times as
strong as aluminum, consequently only 1/3 as much should be required. Since
steel is less than three times as heavy as aluminum, it was postulated that it
might be feasible to build a steel case as light as an aluminum one, and in
the GAU-8 gain as much as 2 cubic inches of chamber volume as well. This
was a goal which no one expected to achieve; however, the objective of our
program was to derive the thinnest, lightest steel case possible. Also, since
steel is much cheaper than aluminum, a cost saving was expected to result.
This was tried under contract to Amron Corporation.

Historical Development Summary of Automatic Cannon Caliber Ammunition.: 20-30 Millimeter [Final Report for Period 1952-1983] - Dale M Davis AFAL Munitions Division (1984)
Grey Havoc said:
Could the Marquardt in question be Frank Marquardt?

Very likely. He designed the USN's 20mm MK 11 cannon, a weird and wonderful gun which was a revolver cannon with eight chambers and two barrels. It was only used in gunpods AFAIK. His original design used strange backwards-loading ammunition which was shot into the chamber at high speed, but the production version had the usual USN 20x110 MK100 series ammo.
More on DACR from Friedman's British Destroyers and Frigates, WWII and After, page 256.

To paraphrase, an immediate post war Anglo-American project, but studies in late 1948 showed that it could not deal with incoming missile. The DACR in question being a notional 34mm gun with a fire-rate of 4,000 rounds per minute.

In Friedman's cruiser book DACR appears in ships until 1949, so perhaps we can assume it is cancelled soon after.

Can anyone find reference to DACR, perhaps under a different designation, in USN books covering the immediate post-war period?
I have very recently been sent some data on the 34mm Class T which was apparently a revolver cannon, but I'm away from home this week so I'll take a close look when I get back.
Okay, I have my source.

A January 1949 report from the Machine Gun Department, Crayford, summarises the Vickers-Armstrong Automatic Gun Class T feasibility study. This was to evaluate the optimum gun design to fire a C.E.A.D. design of 34mm projectile and a cartridge of 30 cubic inches (490cc) chamber capacity. A drawing of the rimless cartridge designed by VA is included; this is 410mm long overall, with a 291mm case length and a rim diameter of 55.9mm.

No ballistics are provided, but this cartridge would clearly have been considerably more powerful than the existing Swiss 34mm Flab.Kan.38, which had a case length of 239mm and a rim diameter of 47.8m, and generated in the region of 300,000 J muzzle energy. For the sake of comparison, the 35mm Oerlikon which replaced the 34mm Flab.Kan.38 in Swiss service in the 1960s - and has since enjoyed considerable international success - has a case length of 228mm, a rim diameter of 54.5mm and generates 380,000-400,000 J (depending on the loading). So the Class T cartridge would presumably have generated at least 400,000 J.

VA looked at three different gun designs capable of handling this cartridge:

Design A: a recoil-operated revolver with six chambers.
Design B: semi-blowback, with the breech unlocked by a gas piston
Design C: recoil-operated with a sliding breech block, unlocked by a gas piston.

Design A was very unusual because all successful revolver cannon have been gas-operated, not recoil-operated. Design B would presumably have used a similar mechanism to the existing 20mm Hispano aircraft gun. Design C is another strange one - a blend of gas and recoil operation.

Design A was selected as the one with most promise and VA were asked to focus on this in completing the design study. However, no more documents have so far been found concerning this project.

Although the summary does not mention the planned end-use for the gun, it seems reasonable to suppose that it was intended for D.A.C.R. (and maybe other applications). Why it did not proceed is unclear. Not long afterwards, the British Army became very interested in 42mm AA guns (see on the Red King and Red Queen projects) but subsequently dropped these in favour of buying the new Bofors 40mm L70. The RN also wanted to buy the 40mm L70 at one time, but did not do so - the naval Bofors guns remained the WW2 era L60 type until they with withdrawn some time in the 1990s. The RN did nothing about replacing the WW2 guns, preferring to focus on guided missiles (Sea Cat then Sea Wolf) until the Falklands experience led to the rapid purchase of various new guns, including manually-aimed 20mm and 30mm Oerlikons and the automated 20mm Phalanx and 30mm Goalkeeper.
Am I right that before the cancellation of DACR weapon system and the GW cruisers the final gun which was considered was the Bofors 40mm/70 m/48?
The Postwar Naval Revolution book by Norman Friedman mentions a sextuple 40mm/70 abortive Mark 12 or XII gun mount for the DACR.
Now question: could the large sextuple mount used on Vanguard retrofitted or slightly modified to accept the longer 70 calibre Bofors m/48 gun? Or does it require a considerable redesign?
The Postwar Naval Revolution book by Norman Friedman mentions a sextuple 40mm/70 abortive Mark 12 or XII gun mount for the DACR.
Now question: could the large sextuple mount used on Vanguard retrofitted or slightly modified to accept the longer 70 calibre Bofors m/48 gun? Or does it require a considerable redesign?
A number of 34mm mountings are mentioned in Warship 2015, with a variety of different feed systems and varying numbers of barrels. A pair of images depicting models of quad and twin mountings, traversing in a similar manner to the Limbo Anti-Submarine Mortar are also depicted.

There was also a twin 57mm mounting mentioned by @smurf here. A sketch appears later in the thread.

DACR only appears on the Cruisers of 1960 (designed in 1948-9) and doesn't reappear until the CR-series of gun cruisers designs in 1951-54. Given that the Bofors L70 appears from the at least 1951 onwards and remains on designs including the GW Series in the late 50s, they may be separate projects. For example, in George Moore's Warship 2006 article on Post War Cruiser Designs for the Royal Navy, the early CR series are described as having DACR whilst later designs in the same series are described as having Bofors Mk11 (the twin L70 mount) and Bofors Mark12.
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My opinion is that the DACR finally "evolved" or changed into the 40mm/70 Bofors gun
My opinion is that the DACR finally "evolved" or changed into the 40mm/70 Bofors gun

I think that is a fair assumption. There doesn't seem to have been much solid work on DACR before the Bofors L/70 came along. We have the various studies of 34mm and 57mm but it seems comparatively little hardware materialised. Beyond the speculated 1950s cruisers it doesn't seem to have featured on any other projects. The sextuple 40mm Mk VI saw compatively little use, 328 were built but only 26 were ever fitted (Vanguard, Ark Royal, Eagle) and they quickly fell from favour, probably because the manual clip reloading could only be done at certain fixed elevations. DACR would have been an ideal like-for-like replacement but never seems to have been considered seriously.

Bofors L/70 appearing in 1948 most have seemed the best and most logical replacement for the L/60 and being lighter than the DACR mounts was better for the weight constrained cruiser designs that followed - saying that, during the development of the GW series and Darings and other destroyers its surprising how often the L/70 was omitted simply to save weight.

DACR could have been very formidable, the closest equivalent was probably the quad 45mm and 57mm mounts the Soviets developed, but just too late as SAMs began to become a reality.
Were there any serious difference between the loading mechanism of the /56 m/36 and /70 m/48 Bofors guns?
I've seen a drawing that for eample there was no serious differnece between the 40mm/43 m/32 and the /56 m/36 guns apart from the longer barrel and some changes to the mounting (at least on the outside, I did not seen their internal workings)
The L/70 guns still use gravity-fed magazines developed from the Model 1936.

To get double the rate-of-fire the main difference was the case ejection mechanism. The loading tray was redesigned so it tilts up after each round is chambered. When the gun fires, the spent case is ejected and as soon as it clears the breech ring it strikes the bottom of the tray, deflecting the case downwards. The rammer then moves forward, pushing the tray down and pushing the next round, which is on top of the tray, into the breech.

The idea of doubling the rate of fire was so that a single mount could replace a twin.
Slight edit to my earlier post, although Bofors designed the L/70 in 1948, the naval SAK did not appear until 1952.

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