autogun said:

gatnerd said: Reportedly to have a mix of 57mm and 40mm guns, which seems a bit odd caliber mix. That may have something to do with the fact that Bofors, who make both the 40mm and 57mm guns, is owned by  BAE Systems...and guess who won the contract for supplying the frigate?  Actually, I don't think that a formal decision about the armament has yet been made.  It would indeed seem odd if two new gun calibres were introduced for a handful of new ships.

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:

BAE Systems will produce and deliver Bofors 40 Mk4 and Bofors 57 Mk3 naval guns for the U.K. Ministry of Defence’s Type 31 general purpose frigate program.

The agreement, through a contract with Babcock International, will supply the Royal Navy with a set of advanced, multi-purpose gun systems for its fleet of five ships, with the first ship expected to go into service in 2027.

The contract includes five Bofors 57 Mk3 medium caliber guns and 10 Bofors 40 Mk4 small caliber guns. Both close-in weapon systems are designed to protect the ships against modern and future complex threats. The guns also offer the Royal Navy optimized ammunition types, including the cost-efficient programmable Bofors 3P all-target munition.

I don't know that it's all that surprising when you kinda look forward at the potential threats and potential hotzones that there's a likelihood of the UK being involved in going forward.

There's a lot of constrained waters and potential foes who have lots of smaller zippier craft etc that could get close and be problematic as well as quite a few places where you could also come under observation from persistent small uav's launched both from naval assets and from shore.

To an extent I can see why you might want to do a bit of layering so that you can dedicate 40's to one threat and 57 to another.

When you look at what navies are actually being used for mostly these days it does make sense.

Especially in light of the way proportional escalation is the rule not the exception now and we see all kinds of actions all over where people just outright Don't use their biggest and best toys unless absolutely necessary.

Having the ability to do an escalation of force ladder with potential threats is definitely an advantage currently and will likely be critical going forward

I'm not complaining about the use of the Bofors guns - both 40mm and 57mm systems appear to be useful and effective. I am surprised because it is much more typical of the RN to select a small number of systems and fit them to everything. So the current automatic cannon is the 30 mm MK 44 (which replaced the 30 mm Oerlikon KCB), and/or the 20 mm Phalanx. While in larger calibres the 4.5" Mk 8 is due to be replaced by the US 5" in new ships.

It doesn't look as if many Type 31 will be built, so to choose new systems in different calibres (with consequences for training, maintenance, ammunition supply chains etc) seems an odd departure from their normal procurement practice.

Possibly this is because BAE has been given a wide latitude to outfit the ships, without a looser control by the MoD, but that's just my speculation.

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

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.