Right up there with rum, sodomy, and the lash.

autogun said:

I am most surprised to read that, according to BAE, the 57 mm and 40 mm Bofors guns are indeed to be fitted to the Type 31:

I'm curious how much size and weight difference there is between the 40 and 57mm naval guns. 

I guess they couldn't fit 3x 57's?

TonyDiG said:

Fielding multiple weapon systems instead of standardization on a few is kind of a hallmark of the RN, no?

Not in recent decades, I would have thought. After the Falklands the 40 mm Bofors was replaced by the 30 mm Oerlikon, and that is still in service - in the process of being replaced by the 30 mm MK 44. The 4.5 inch Mk 6 gun was being replaced by the Mk 8 around the Falklands, and the Mk 8 went on to be the sole medium-calibre gun (it still is, the 5 inch not having entered service yet). The 20 mm Phalanx was adopted after the Falklands and (with the addition of a few 30 mm Goalkeepers as part of a swap deal with the Dutch) has remained the RN's CIWS. 

To adopt two new calibres of automatic cannon at one time, in the same ship, is definitely unusual.

gatnerd said:

I'm curious how much size and weight difference there is between the 40 and 57mm naval guns.  I guess they couldn't fit 3x 57's?

The 40 mm guns are the new lightweight Mk 4 - from my forthcoming book:

The latest naval mount is the BAE Bofors 40 Mk 4, which weighs less than 2,500 kg complete with 100 3P rounds – 30 in the primary magazine plus another 70 in an intermediate magazine, from which the primary magazine is automatically topped-up. The fully enclosed turret uses electric drive rather than hydraulics and is fully digitised and modular in the modern fashion. Local control is possible using a gun-mounted video sight. The rate of fire is variable between 30 and 300 rpm.

Development was completed with sea trials in 2011-2012, and the launch customer is Brazil, with five mountings ordered for patrol vessels.

Looks as if I'll have to add to that! And the 57 mm Mk 3:

The current version of the gun is the SAK 57 L/70 Mk 3, a modified version of the Mk 2 designed to use 3P (prefragmented, programmable, proximity-fuzed) ammunition. There is also a muzzle-velocity radar to assist the FCS, and an electro-optical manual aiming system. The weight is increased to 7,000 kg (7,500 kg in the US version). The prototype emerged in 1995 and entered service in 2000 in the Swedish Visby class corvettes, this version being in an optional 'stealth' mounting, with a gun barrel which disappears into the mounting when not required. The Mk 3 has been selected (with a conventional mounting) to arm two new US warship projects: Coast Guard cutters, and the Littoral Combat Ship. In US service the gun is designated the MK 110 Mod 0.

So the 57 mm weighs about three times as much as the 40 mm.

"The 40 mm guns are the new lightweight Mk 4 - from my forthcoming book:"

Nothing like having the guy who literally wrote the book on the subject provide the answer ;-) 

Being 1/3 the weight would make sense for why they went 2x40 + 1x57 vs attempting 3x57. 

autogun said...

Not in recent decades, I would have thought. After the Falklands the 40 mm Bofors was replaced by the 30 mm Oerlikon, and that is still in service - in the process of being replaced by the 30 mm MK 44. The 4.5 inch Mk 6 gun was being replaced by the Mk 8 around the Falklands, and the Mk 8 went on to be the sole medium-calibre gun (it still is, the 5 inch not having entered service yet). The 20 mm Phalanx was adopted after the Falklands and (with the addition of a few 30 mm Goalkeepers as part of a swap deal with the Dutch) has remained the RN's CIWS. 

To adopt two new calibres of automatic cannon at one time, in the same ship, is definitely unusual.

Yes, I agree completely, just making a joke.  Although the RN is adopting two new guns, these are not new mounting designs and the guns themselves have been around for quite some time.  That lowers the risk considerably.

autogun said:

I somehow doubt that they are going to be firing Orkas at 220 rpm.... scream Incidentally, I find it hard to comprehend US designation systems. The ordinary 57 mm HE shell is the Mk 295, yet the Orka is the "Mk 295 Mod 1". That's one hell of a Mod!

That strikes me as a Tu-29M kind of designation ...

autogun said:

Possibly this is because BAE has been given a wide latitude to outfit the ships

Speculation confirmed - I've just been reading an article on the gun armament of the Type 31 in Warship World magazine:

"Type 31 acquisition strategy adopted a whole ship procurement model with minimum mandated equipment or government furnished assets/information. This meant the competing teams were largely free to make their own choices with regard to major platform systems, power and propulsion, and combat system equipments."

The article includes a detailed description of the ammunition for the 40mm and 57mm guns, and mentions a couple of guided 57mm rounds currently under development in the USA:

"The first of these is the High-Explosive, 4-Bolt Guided (HE-4G) projectile being developed by L3Harris Technologies under the Advanced Low-Cost Munitions Ordnance (ALaMO) programme (which is) intended to provide the navy with an improved smart round able to hit moving air and surface targets at significantly longer ranges.....the HE-4G round (designated MK 332 Mod 0) includes a radio frequency guided projectile.

The second development, known as MAD-FIRES (Multi-Azimuth Defense Fast Intercept Round Engagement System) is being led by DARPA. The concept is to combine the guidance, precision and accuracy of missiles with the speed, rapid-fire capability and large magazine capacity afforded by the 57mm. It is a rocket-assisted round with a terminal seeker to home onto an illuminated target."

Of course, there is no commitment at present to acquire these rounds by the RN, but it would be nice to have the option available.

Anyone know what the "4-Bolt" means?

autogun said:

Anyone know what the "4-Bolt" means?

It's apparently a reference to the course-correction method -- it has a set of four weights (bolts) that it can expel laterally to adjust the projectile's trajectory.

Edit: I finally found a video that shows this in decent detail.  https://www.youtube.com/watch?v=vY9rJBL1S2Y&feature=emb_title&ab_channel=L3Technologies

Thanks - interesting!