Type 31 Light Frigate – Weapons options

By Jed Cawthorne

01.  Introduction
02.  Overview of the Arrowhead 140 design
03.  The need for more guns
04.  Italian style and flair
05.  Summary



Babcock Type 31e Light Frigate Proposal (Image: Babcock International)

01.  Introduction

With the cost of of Type 26 ASW Frigates and Type 45 AAW Destroyers running to up to £750 million or £1 billion per ship, the total number of vessels that can be afforded by the Royal Navy has been reduced. Since no ship can be in two places at the same time, there comes a point where absolute ship numbers cannot be reduced beyond a certain level. That number appears to be 19 surface combatants. With six Type 45 Destroyers and eight Type 26 Frigates, there was a need for a low-cost general purpose frigate. This requirement will be filled by the Type 31e Light Frigate (no one use the word Corvette).

Over the past two years, the Royal Navy has evaluated three bids from Bae Systems / Camell Laird, Babcock and Atlas Elektronic UK. In September 2019, at the DSEI Defence exhibition, the Government announced that the Babcock Arrowhead 140 designhad been chosen as the RN’s preferred Type 31e Light Frigate option. Following-on from this, there has been much conjecture about how this new class of ships will be equipped, including the combat management systems, sensors and weapons. An excellent analysis of this can be found at: https://www.savetheroyalnavy.org/more-details-of-the-royal-navys-type-31-frigate-emerge/

There is some concern that the proposed weapon fit will not deliver sufficient firepower for the roles envisaged, especially when new threats, such as drone swarms, fast attack craft and hypersonic missiles are considered. Therefore, this article will look at the proposed weapons and consider whether better options exist. This discussion does not limit itself to Type 31e and some of the weapons currently under consideration for this warship could well be used across the fleet.

Babcock model of its Type 31e Light Frigate proposal showing different weapon fit options. (Image: Nicholas Drummond)

02.  Overview of the Arrowhead 140 design 

The Type 31e Frigate is intended to provide the Navy with an inexpensive general purpose warship with the range and endurance needed for global maritime security operations. It must be able to operate alongside Type 45 Destroyers, which are specialist anti-air warfare ships, and with the new T26 Frigates 3(or Global Combat Ship) which are specialist anti-submarine warfare ships. The Babcock Arrowhead 140 design is based on the Danish OMT design bureau’s design for the Danish Navy’s Iver Huitfeld-Class of AAW Frigates 4, which in turn is based on the earlier Absalon-Class multi-role support ship.

The Arrowhead 140 displaces 5,700 tonnes, measures 138m in length, is 20m wide and has a crew of potentially less than 100, but accommodation for 180. With a proven hull, it is notably larger than other vessel designs submitted for the competition.  In contrast, my first ship, HMS Hermione (F58) which I joined in 1984, was a Batch 3 Sea Wolf Leander-Class Frigate.She was the last RN ship to be refitted in Chatham Naval Dockyard and also served as a general purpose light frigate. She displaced 3,300 tonnes (fully loaded), measured 112m in length and was 13m wide. The steam-powered Leanders required a crew of 250. She was armed with the Sea Wolf GSW25 point defence missile system, 4 x Exocet anti-ship missiles, 5 x 20mm cannon, 2 x triple torpedo tubes, and a Lynx helicopter with Stingray torpedoes or Sea Skua anti-ship missiles.

As the difference in displacements shows, the modern Type 31e GP frigate will be much larger, offering better sea-keeping abilities, greater range and endurance, and more modern, comfortable living conditions for her crew. Four reconfigurable boat bays plus additional crew accommodation mean that RN boat crews or RM boarding parties will be able to provide excellent maritime security capabilities, supported by either a Wildcat or Merlin helicopter. A bank of 24 Sea Ceptor / CAMM surface-to-air missile cells amidships will provide cutting-edge short-range anti-missile / anti-aircraft capabilities. The new vessel is also expected have a hull-mounted sonar that is at least equivalent to that of Type 45 Destroyer and the ability to embark a Merlin Mk2 ASW helicopter, to provide baseline ASW capabilities. These could be enhanced by adding Unmanned Surface Vessels for ASW in place of some boats and potentially a containerised towed array sonar in the deck mission space below and behind the flight deck, which will be able to carry multiple 20-ft ISO containers. Additionally, the RN has issued an RFP for a new ‘Interim Anti-Ship Missile’ to replace the obsolete Harpoon used on the five existing Type 23 GP Frigates.

The main search radar will likely be the Thales NS110 AESA radar or possibly the newer NS200 GaN AESA set. With detection ranges of 110 miles or more, these systems are comparable in performance, but lower in cost than the similar BAE Artisan system used on Type 23, the QE carriers and Type 26. Decoys are likely to be the standard RN DLF floating radar decoys and Sea Gnat Chaff/IR flare mortar system, lifted from decommissioned Type 23s.

Ultimately, the size and flexibility of the Type 31e vessel means they can be expected to have a meaningful role within a carrier task group, even if their main role is to deploy globally on maritime security operations, allowing Type 45 Destroyers and Type 26 Frigates to focus on Carrier Strike Group operations. The low cost and modularity of the design also means the ship could have significant export potential.


03.  The need for more guns

After the DSEI announcement, details started to emerge of the proposed weapon fit for Type 31e. While no official details have yet been released, the following weapons are expected to be fitted:

  • Main gun – 57 mm Bae Systems / Bofors Mk 3 / Mk. 110 gun8 with rapid fire capability and a 10.6 mile / 17 km range
  • Secondary gun – 40 mm Bae Systems / Bofors Mk. 4 gun9with the ability to engage air and surface targets, making it ideal for neutralising fast attack craft and with a range of 12 miles / 19.2 km
  • Air defence – 24-cell Sea Ceptor / CAMM VLS
  • Point defence- 2 x 30 mm SCG / ASCG cannons7 mounted aft
  • Point defence – 2 x 7.62 mm miniguns mounted forward
  • Decoy system – 2 x Sea Gnat decoy launchers (From Type 23)
  • Space for Anti-ship Missile canisters – TBC
  • Miscellaneous weapons – 2 x 7.62 mm GP machine guns

Assuming the above configuration is correct, the choice of weapons may not provide sufficient firepower in all situations, making the Type 31e a larger version of a lightly-armed OPV (albeit one with a SAM capability).

Bae Systems / Bofors 57 mm Mk 3 / Mk 110 gun (Image: Bae Systems)

As the ‘Save The Royal Navy’ article notes, the 57 mm Bofors and 40 mm Bofors both make sense if the T31 has to counter small boat swarms, attacks by suicide boats, helicopters, light aircraft, or even drones. It also states that fitting the BAe 127mm / 5-inch gun,10 which will be mounted on the Type 26 Frigate, is considered to be too expensive for Type 31e. With the Type 45 AAW Destroyer continuing to use the ubiquitous 4.5-inch gun, the multi-role, but ASW focused Type 26 will adopt a NATO-standard 127 mm / 5-inch gun, acquiring a third type of smaller gun for  Type 31 seems short-sighted.

Fitting a 127 mm gun is perfectly valid for a Type 26 ASW Frigate, giving it flexibility and lethality across a range of situations, its primary role will be ASW, so it would be expected to use its main gun less than a Type 31e will, especially as Type 26 also has VLS launch tubes for anti-ship missiles such as Tomahawk or whatever replaces Harpoon. In case the capabilities of a 127 mm gun are required, the Navy would need to detach a Type 26  for use in littoral waters and give it a Naval Gunnery Support (NGS) mission on the ‘gun line’ – which is actually where Type 31e should come in. In other words, the 127 mm gun is more appropriate for Type 31e than it is for Type 26.


Bofors 40mm mk4
Bae Systems / Bofors 40 mm Mk 4 gun (Image: Bae Systems)

Introducing the Bofors 40mmto the RN adds greater range while offering more a more flexible range of ammunition than the current 30mm Mk44 Bushmaster in its MSI Seahawk 12lightweight remote mount. The BAe FUZE 3P programmable fuse with pre-fragmented rounds for both the 40mm and 57mm guns gives them excellent anti-small boat swarm performance, and even an anti-missile capability. Despite a lower rate of fire, HE proximity fuse rounds can throw an impressive cloud of shrapnel at an incoming missile at double the range of a stream of 20mm projectiles from a Phalanx CIWS.14 Thus, adding the Bofors 40mm gun to the inventory and supply system makes sense if it is to be used widely to replace the Phalanx in various vessels. I am no fan of the Phalanx, it was introduced to the RN at the same time as I was, in the early 80s, and I have had two different careers since, so hope to see it retired in favour of a more modern and capable system. As good as the Bofors 40 mm is, there are better alternatives, including the latest modifications to remote 30mm mounts that add five Martlet laser-guided lightweight multi-role missiles (LMM).12There is also the Thales RapidFire,15a turret mounted 40mm CTA cannon with air burst ammunition (although Thales suggests that a 200 rpm gun is not really an anti-missile system).

General Dynamics Phalanx 20 mm CIWS (Image: Naval Today)

Perhaps though, the best alternative to the Bofors 40mm, for a fleet wide fit, would be its big brother, the 57 mm Mk3, widely deployed in the US Navy as the Mk110 gun. The turret has a non-deck penetrating mount and weighs 7 tonnes . It is capable of 220 rounds per minute out to 17 km against surface targets. As noted above, it can use the same advanced fuse system as the 40mm, providing an air-burst capability against air and surface targets, as well as impact detonation, or delayed action against bigger surface or land targets. Even more interesting is the BAe ORKA16advanced ammunition. The ‘Ordnance for Rapid Kill of Attack craft’ is a 57mm guided round with anti-surface and anti-air capabilities. These are provided by an imaging seeker that can also lock-on to an illuminated laser reflection. Beyond ORKA is DARPA’s MAD-FIRES, a 57mm gun launched point-defence anti-missile missile. Details about this can be found on this video: https://youtu.be/HGV5fYluOu4


DS30 Remote Automatic Cannon – MSI Seahawk mount with Bushmaster Mk44 gun and 5 x Thales Martlet (LMM) missiles.(Image: Jed Cawthorne)

With ORKA and 3P ammunition, a turret with a hoist, with an ammo handling system for 1,000 rounds (for applications where deck penetration is not a problem), and weight of 14 tonnes, this is an extremely flexible weapons system. A magazine-fed system in B and Z positions on the T31 would provide a fantastic anti-swarm capability. As we are unlikley ever to send one of only six highly specialised (and costly) Type 45 AAW Destroyers to provide NGS missions, it might make sense to remove the 4.5 inch Mk 8 from use and replace it with a 57mm Mk. 3, plus replace Phalanx with non-deck penetrating 57mm turrets.

Apparently, there were some comments at DSEI about improving the lethality of the Batch 2 River Class OPV’s – replacing their forward 30mm mount with a non-deck penetrating 57mm Mk3 mount would provide a considerable uplift in capability for these vessels.

04.  Italian style and flair

The Bofors 57mm is not the only game in town. Many of our European Naval allies use the Leonardo / OTO-Melara 76mm Super Rapid gun.6  With an even greater range than the 57mm gun, it has similar advanced fused ammunition types, giving it a multi-role capability as well as using standard HE ammunition.17It has an interesting sub-calibre round called the DART, which is radar guided as part of the STRALES system, providing a guided anti-missile capability.18The standard air-burst HE rounds are useful for dealing with small boat swarms, but a 76mm version of the Vulcano 19provides extended-range unguided and guided capabilities against larger enemy ships and surface targets. OTO-Melara’s scaled-down version of their 127mm projectile,20which we could fire using our BAe Mk45 127mm / 5-inch guns. The Italian Navy mounts multiple Super Rapid guns on its Frigates and Destroyers in the CIWS anti-missile role. German, Dutch, Danish and Spanish navies all use older versions of the same 76mm light gun.

Leonardo / OTO-Melara 76 mm Super Rapid gun (Image: OTO-Melara)

05.  Summary

Advanced electronics applied to ammunition fuses, advanced materials used for lightweight mounts with ballistic protection, advanced barrel designs that offer improved ranges and automatic ammunition handling systems that offer higher rates of fire are driving a renaissance in naval gunnery, from 30mm up to 127mm. These advances can improve the self-defence and offensive capabilities for RN ships, from River class OPV’s to the QE class carriers.

As the Type 23s are eventually replaced by the Type 26 with its 127mm gun, and by the Type 31e, we should seize the opportunity to remove the venerable and ubiquitous 4.5 inch from service. We could replace the 4.5-inch gun on the Type 45 with a 127mm, but do we really need to? The Type 31e, however, as a General Purpose Frigate, that does not perform specialist deep water AAW or ASW roles, should really be a candidate for a 127mm main gun, giving it littoral combat and NGS capabilities for its ‘high end conflict’ role within the overall fleet.

The Bofors 57mm has the flexibility to replace the Phalanx CIWS on the Type 45 Destroyer and Queen Elizabeth-Class Carriers and potentially on some RFAs too. While the 57mm is no doubt more expensive than the Bofors 40mm, I question the cost of introducing a third new mount with the attendant training, maintenance, supply chain and ammunition supply burdens. In some respects a 30mm DS30 mount with five Martlet missiles has an advantage over the 40mm, while the 57mm has range and ORKA in its favour. So if we could afford it, it would be good to see the future fleet equipped as follows:

Type 45 AAW Destroyer

  • 57mm with magazine in A mount replacing 4.5 inch gun
  • 57mm non-deck penetrating mounts port and starboard to replace Phalanx
  • Port and starboard DS30 remote mounts with Martlet

Type 26 ASW Frigate

  • 127mm Mk45 in A mount
  • 57mm port and starboard non-deck penetrating mounts instead of Phalanx
  • Port and starboard hanger roof DS30 remote mounts with Martlet

Type 31 GP Light Frigate 

  • 127mm Mk45 in A mount
  • 57mm deck penetrating with magazine in B (in front of bridge) and Z (central hanger roof) positions
  • Port and starboard hanger roof DS30 remote mounts with Martlet

River Batch 3 Offshore Patrol Vessel

  • 57mm non-deck penetrating mount in A position
  • Port and starboard DS30 with Martlet abaft of boat davits

In conclusion, this mix of weapons amounts to a lot of 57mm gun turrets, but there is much to be said for standardisation and commonality of spares, training and ammunition. This would give each major surface unit five gun mounts, with a mix of 127mm, 57mm and 30mm. A bit better than the 5 x 20mm manually aimed guns of my first ship, and better than the 4.5 inch, 2 x Phalanx and 2 x 20mm of my final ship, the T42 Destroyer HMS Glasgow.




  1. Babcock Arrowhead 140 Site – https://www.arrowhead140.com/
  2. org – More details on the T31 – https://www.savetheroyalnavy.org/more-details-of-the-royal-navys-type-31-frigate-emerge/
  3. BAe Systems Global Combat Ship (RN Type 26) – https://www.baesystems.com/en/product/global-combat-ship
  4. Danish Iver Huitfeld Class – https://en.wikipedia.org/wiki/Iver_Huitfeldt-class_frigate
  5. Leander Sea Wolf / Exocet conversion – https://en.wikipedia.org/wiki/Leander-class_frigate#Batch_3,_Seawolf/Exocet_conversion
  6. Leonardo OTO Super Rapid 76mm light weight naval gun – https://www.leonardocompany.com/en/products/76-62-super-rapid
  7. DS30BM 30mm Remote mount with Bushmaster M44 30mm cannon – https://en.wikipedia.org/wiki/30mm_DS30M_Mark_2_Automated_Small_Calibre_Gun& https://www.msi-dsl.com/products/seahawk-ds-remote/
  8. BAe Mk110 / Bofors 57 Mk 57mm system – https://www.baesystems.com/en/product/57mm-naval-gun-system
  9. BAe Bofors 40 Mk4 Naval gun – 40mm cannon – https://www.savetheroyalnavy.org/more-details-of-the-royal-navys-type-31-frigate-emerge/
  10. Bae Mk45 Mod 4 127mm Naval Gun – https://www.baesystems.com/en/product/mk-45-mod-4-naval-gun-system
  11. 5 Inch / 114mm Mk 8 Gun – https://en.wikipedia.org/wiki/4.5-inch_Mark_8_naval_gun
  12. DS30BM mount with Martlet (Light-weight Multi-role Missile) – https://www.msi-dsl.com/products/msi-ds-seahawk-sigma/
  13. Fuze 3P – 57mm multi-purpose ammunition – https://www.baesystems.com/en/product/fuze-3p-ammunition
  14. Phalanx 1B 20mm CIWS – https://www.raytheon.com/capabilities/products/phalanx
  15. Thales RapidFire 40mm CTA turret – https://www.thalesgroup.com/en/worldwide/defence/rapidfire
  16. BAE 57mm ORKA – https://www.baesystems.com/en/download-en/20170726161933/1434555371520.pdf
  17. Leonardo 4AP programmable fuze for 76mm and 127mm ammunition – https://www.leonardocompany.com/en/products/speltta-4ap?f=/sea/weapon-systems/ordnance-ammunitions
  18. DART guided sub-calibre projective for 76mm SR gun – https://www.leonardocompany.com/en/products/speltta-4ap?f=/sea/weapon-systems/ordnance-ammunitions
  19. OTO Vulcano 76mm extended range / guided munition – https://www.leonardocompany.com/documents/20142/3150950/OTO_VULCANO_76_LQ_mm08725_.pdf?t=1538987712848
  20. OTO Vulcano 127mm extended range / guided muntion – https://www.leonardocompany.com/documents/20142/3150932/OTO_VULCANO_127_LQ_mm08724_.pdf?t=1538987710000



  1. Screams at the lack of standardisation and additional cost of keeping different ammo types that serve the same role. Honestly? just go to 90mm don’t bother with the 76mm we have stocks from the army of old ammo that can be fit to new guns. Scorpion 90 and similar.
    30 to 35mm rounds, auto cannon, a lighter cannon, More ammo being more important. and missles, lots and lots of missles 170mm+. not cheap. and why not do what the russians do. and have the same HE shell for both tanks and Ships? as they use the same 125mm guns?


    1. We could not use for example the Challenger 2’s main gun on a ship. The 120mm L30A1 although an excellent gun, is not designed for a sustained rate of fire like the AS90’s 155mm L31 gun. Yes, both have very high pressure ratings, but the L31’s barrel is substantially thicker. This is to allow heat dissipation during sustained firing and slow down the barrel warping. The L20A1 of the Chally is thinner for weight saving and is only designed to fire off its magazine in one go. The AS90 by comparison does have a limit on how long it can sustain firing but its at least 5 times as long as the Chally.
      The Scorpians we had in service never had the 90mm gun that was used on the export versions.
      The 57mm and 76mm are now standardised sizes Worldwide, it makes sense to stay with these sizes rather than creating a new size on cost grounds alone. A good example is how expensive the CTAS 40mm rounds cost compared to “normal ” 40mm rounds which are at least double the cost. Yes the barrel is the same as any 40mm barrel, the feed mechanism and breech however are completely different, so nothing from another weapon system could be used.
      On another furm we discussed the merits of both the 57mm and 76mm gun. With the 76mm winning due its shell having a greater explosive content when used for surface action or NGFS. With both weapons having guided rounds for AAW so there’s little to choose between the two, except the Dart round having again more explosive content.
      The main difference is that the 76mm requires a below decks magazine if its using the Strales system which includes Dart and Volcano ammunition. Whilst the 57mm can be used from a pedestal mount with no deck penetration and still use the guided rounds.
      We concluded that the 57mm would be the ideal replacement for CIWS and its also a multi-purpose weapon compared to the Phalanx.


      1. What about a SPAAG turret on a ship? was that ever trialed? In regards to chally 2 i think an upgrade/ new tank is required before 2035 with a smoothbore gun due to prices of ammo and the worlds rejection of rifling… i still want HESH!
        Honestly i think we should go up in caliber for our field artillery, tracked artillery and naval guns, all smoothbore. Something between 165mm and 178mm which would enable us to build, and not only make viable, rocket assisted ammo (as tested for m777) and makes for a easily mass produce able rocket for jets and heli’s. as fuses and fillers can be same diameter, and the machines that make the ammo can be mass produced to produce more ammo, incomparison to just making dedicated missle components and dedicated conventional rounds.
        But as you describe barrel thickness and mass is going to be an issue regarding anything land based, less so on a ship. unless its something rapid and light.


    2. I’m sorry but we’ve never had Scorpion 90 or any 90mm shells in the recent UK inventory. I am pretty sure the last time we had 76mm was on scorpion and about 20 years ago. I really think that commonality especially between the army and navy is overrated, the main thing is that ammo is in wider use with NATO allies both the 76mm and 127mm tick this box. Also the Russians do not use 125mm at sea and there is a massive difference between artillery firing at tens of kilometres plus and tanks shooting in parallel with land where approx 5km has been the longest kill.


    3. I am wrong on the ammo front as pointed out by atleast two people (i can’t edit for some reason??????), but a case for a standard caliber has been made since the end of WW2, we have a plethoric amount of diameters of ammo, can we just focus on a few of them. I will agree ship guns are not land guns mounted however you please. however most arguments are coming from A) barrel wear and B) range, i will counter with ships and land guns , can have same ammunition, but naval guns, will have longer barrel lengths. to accommodate for the range.
      Also things i don’t understand. her majesties navy—- 4,5″ 114.3mm QF
      her majesties army’s tank armament—- 120mm 3 part ammo
      we did trial a 155mm gun, shared with the AS90 but it was rejected, because the brass are weird, 2 it was not designed in partnership only a second idea afterwards and was not optimised for that role.


      1. The Russian Navy are introducing a new CIWS that replaces the Kastan system, this is Panstir-M. The Pantsir system originally started as a truck or track mounted SPAAG that either travels with a battle group or is part of the low level screen for the S300/400 SAM system.
        The system has been marinised and can operate fully independently of the ship’s systems. If more than one system is fitted to a ship they can be networked together, much like the Phalanx.

        Liked by 1 person

  2. I understand small caliber gun 57mm against fast moving air targets as well as ships – except possibly against an unarmed freighter, or a surfaced damaged submarine, not worth a missile.


  3. Oops
    I understand small caliber gun below 57mm against slow moving aerial target (UAV, helicopter) with secondary use against speedboat.
    I fail to understand the value of higher caliber above 57mm against fast moving aerial targets or ships – except possibly an unarmed freighter or a surfaced damaged submarine, not worth a missile.


  4. If we truly think we cannot afford the super expensive 5 inch / 127mm BAe Mk45 for the T31, and yes it is very expensive (why?) then I would modify my outfit to:

    A mount (fcsle) 57mm
    B mount (center line in front of bridge) – ASCG 30mm with Martlet
    X and Y mounts (port and starboard hanger roof ) – ASCG 30mm with Martlet
    Z mount (center line hanger roof) – 57mm

    There would be an argument that without a 127mm then the 76mm might be better for T31, but I am looking for standardization across the fleet, and a reason to not introduce yet another gun / caliber (40mm or 35mm) specifically as a CIWS if the 57mm can do that job.

    So, same as DavyB’s comment above, ref a similar discussion in a different forum, I have definitely warmed to the 57mm while researching this article and find it’s multi-role utility, cost and wide spread use by allies to be a convincing argument for widespread introduction to the RN, as long as that involves removing Phalanx (keeping maybe for the RFA flotilla) and 4.5 inch from service as soon as possible to gain maximum benefits of standardization.


  5. I do like the proposed weapons fit and I do rate the 57mm it looks a very good system for ciws and anti-FIAC. In terms of T31 If we were purchasing a LCS fine as a main armament, but we are supposedly getting a frigate and for me this is where it falls down.

    Although a number of critics say NGS is dead due to anti-ship missiles, if you’re a Royal Marine or paratrooper in the early stages of a amphibious landing it can be a life saver and not only that a campaign winner. Due to the threats the 127mm with a possible 100km+ range is a must and not only that it is really the only system that can deliver the weight of fire required. Time and time again the RN have balanced threats and concluded NGS is worth the risk. In the Falklands, 2nd Iraq war and Libya therefore we should give them the best tools to the job.

    I still would like it on T45 as I can see a scenario where it is forward deployed protecting amphibious ships especially as due to slow landing craft we have, we will have expensive ships with lots of precious human lives close to the shore. In this scenario the height and capability of Sampson combined with CAMM land and sea as well as Crowsnest could greatly increase survivability of the ships. The T45 capabilities would hopefully mean fewer ships would need to be deployed allowing it to engage aircraft without so much clutter. So whilst it is deployed there, the addition of 127mm could be very useful.

    I would guess the most important words are “if we could afford it” if not I would prefer the 4.5 inch & either 2 x 57mm or 2x40mm. However my suspicion is that the RN may have found a buyer for the T23s, countries such as Brazil, Chile and Romania seem to have bought equipment we thought unsustainable and ageing and made it work.

    In this event I can’t see the 127mm being affordable and considering the importance the RN has put on NGS the only option for me then is the 76mm simply because of the larger shell and significant range advantage (x2 with vulcano) offered over over the 57mm. Also it will deliver a similar effect of 57mm but with less shells. Yes it will need some infrastructure but there is space in T31 and this infrastructure will allow more sustainable fire versus 57mm that would be reliant upon what is stored in it’s housing.


  6. So the 4.5inch guns are good, we still have ammo and if we can put them into a stanflex module like the IH class then we should use these for the T31 and put 2 57mm in the B and Z positions.

    It’s the best of both worlds as 4.5 is with us until T45 retire and they were upgraded in the last 20 years (the 57mm is over 60 years old so no problem).

    We will still have the 4.5 gun we may as well use it and that will make the T31 very capable indeed, in fact it will be more potent than its current set up and we wont need to introduce the 40mm set up.

    This means the RN will have 4.5, 5, 57mm and 30mm guns and I would move the 30mm onto RFA vessels only.


    1. To be honest I am confused at how little GFE is being used in T31. I can only assume it is down to striping and integration time unless we do have a buyer. But considering some of the potent weapons and systems on the ship particularly the 4.5 inch and almost as importantly the 2050 bow sonar. Why are we spending more to give new ships a potential inferior weapons fit when we don’t have to????


  7. Many thanks for again putting pen to paper.
    A Mk45 would be the starting point for me, I agree with Simon that NGS is at risk and would note that (iirc) the navy added a main gun to the Batch 3 T22 as a direct result of their experience during the Falklands war, this despite their horrifying ordeal at the hands of Exocet.
    I don’t see what has changed except maybe the gun, you’re looking at pinpoint precision and ranges out to 100km, couple that to a drone or a covert recce and you have an extremely useful tool for low to high end.
    I also disagree somewhat with the preoccupation everybody seems to have with speedboats and pirates.
    I would argue for the 32 Mk41 it’s rated for, either to slot it into a carrier battle group or for it to stand its ground in the littorals.
    I do realise that the above is a £100m ask, but the numbers in my brain seem to work, although I would have to get a little creative and bend the navy about a bit.


    1. It would be interesting to read how you would ‘bend the Navy’ to make this work within the existing budget. Personally I am pleasantly surprised at the reported weapons/sensor fit given the budget. If they could squeeze some more out of it I would prioritise fitting whatever replaces Harpoon for surface/land strike.


      1. It’s a bit lengthy and not really on topic (sorry and thank you again Jed), so maybe look at this post in isolation.
        As I noted on STRN given the build rate of T26 then T45 will need replacing around ship 7, so cancel ASW 7 and 8, add that money to the pot and build an AAW warfare suite straight into T26 for T26 seven through twelve on the T45 replacement budget.
        Take the billion for MCM and add that to the pot and your original T31 budget puts you somewhere around £4bn which gives you twelve high end T31 replacing GP T23, survey, Rivers, MCM’s.
        It’s pretty much the C1, C2, C3 argument.
        Rather than using the transformation fund to progress littoral strike (which I don’t really view as transformative as we did that in Suez) use it to create MCM teams using offboard systems to operate from any fighting or support vessel, or indeed from shore; the direction of this technology I think is pretty clear now and the navy would likely end up with four vessels along the lines of the MBT Venari. Further, use this funding (if it still exists post Gavin) to look at shore based alternatives for TAPS such as the US is doing with ‘Sea Hunter’.
        I think such investment would better be described as transformative.
        The littoral strike concept would then be met under the replacement program for the Point Class, STRN presenting a useful looking contender in the form of Prevail Partners MRV for the sake of example.
        Albion and Bulwark could then be replaced by dedicated vessels somewhere down the line, hopefully in the form of LHD’s.
        To my (admittedly simple) mind that looks like you get enough T26 to constantly alternate a CBG and an ATG (or to combine the two for out of area ops) and enough T31 to meet your other standing commitments.
        I’m pretty much arguing for what the navy said and against what it is saying.
        Regards, Nemo


  8. I support the idea of standardising on the 30mm, 57mm and 5 inch guns across the fleet. To that end I would agree with not going with the 40mm on the T31 and instead going with a non deck penetrating 57mm on Z mount and a deck penetrating 57mm with magazine on B mount leaving A mount free for a future 5 inch.
    There is rumour of a possible further 3 T31 after the intial first batch of 5.
    With that in mind I would suggest taking 4 of the 5 inch guns planned for the T26 programme and fit these to 4 of the T31s and give 4 of the T26 the 57mm instead.
    This would leave you with 4 T26 with 5 inch and the other 4 T26 with 57mm.
    And likewise 4 T31 with 57mm only and 4 with 57mm and 5 inch.
    For a typical carrier delpoyment with 2 T26 you could have one of each variant. And you could have a 5 inch goalkeeper T31 to send to the gunline without having to reduce your ASW picket screen by 50%.
    The group still has access to two 5inch guns but has greater flexibility if it wants to use them.
    As production has started on the first three T26 the 5 inch may already be locked in on these.
    Of course the Gold Standard would be 5 inch on all T26/31.


  9. Having given this some thought.

    I don’t think the currently envisaged T31 guns fit is inadequate at all. Clearly it all depends what you want the ship to do but it does seem to me to be credible, particularly if ASuW missiles were to also be fitted.

    One needs to guard against a Christmas tree approach to T31. Sure they’re are lots of things you could hang off it (guns, torpedoes, missiles, sensors etc), but just be careful not to undo the concept of a lower cost general purpose frigate.

    On the guns proposal for batch 2 Rivers, this clearly depends upon what it’s going to be used for. Its current 30mm fit is clearly defensive in nature, as would even adding Martlet missiles be. It does strike me that adding a 57mm gun would start to give it a noticeable offensive capability; and you could also then say why not add surface launched Brimstone or even a surface launched version of Wildcat’s Sea Venom. The only question these would beg (apart from £ millions) is what is the actual role of batch 2 River, coastal patrol or a modern day Palmerston’s gun boat ?


  10. Thank you all for the comments and your ideas. Some further comments:

    1. Arming River B2 with a 57mm – not actually my idea, apparently heard being discussed at DSEI in the context of “improving the lethality” of the Rivers. There as an article about them being so expensive because of the high DC standards they are build to etc, so we may consider them “minor war vessels” and make them more punchy / fighty? Big question is that mentioned above – what for? What do you expect them to be able to do with such a capability? First thought is that they would be a survaillance asset that would have very good self protection abilities. Other potential use cases I leave up to you.

    2. Twitter user @EngagingStrategy pointed out that a non-deck penetrating Mk110 57mm still weighs over twice as much as a Phalanx, so the deck might need strengthening at the mid-ships mounting points on the T45 and T26 – this is a good point and while easily within the bounds of naval architecture, this does would have an associated cost. Hence his preference for the Bofors 40mm, which he see’s being in the sweet spot for CIWS. I have now seen a YouTube video from NavalNews from DSEI where the 40mm is mentioned.

    If we went with the 40mm for CIWS, then I would go with one of the comments above and up the game and go with the OTO 76mm SR rapid for F’csle A mount positions where you can have an ammo hoist / magazine, so say T45 to replace 4.5 and T31.

    However he also makes some strange points about how a 5 inch gun needs more personnel, both maintenance and operational, while stating the cost is all about the new automated magazine. Well if it’s expensive because it’s automated, it probably needs fewer people? Either way “back in the day” I don’t remember an army of WEM’s and Gunner’s being needed for the 4.5. So I am not sure that these are good arguments to not put the Mk45 on the T31. Maybe just go old school and fit the old model without the super duper automated magazine?

    Anyway, it appears we have many options, and on the CIWS front I would be more than happy to see a Bofors 40mm with 3P, a 57mm with 3P ammo, or even a Thales 40mm CTA mount (with integrated Star Streak like the land based model!) – anything would be better than Phalanx which has been in use for well over 30 years now.


  11. Jed, thinking about the 57 mm and 40 mm. These are excellent systems and make me wonder if they have land applications. A 57 mm gun on Ajax wouldn’t be a bad thing, especially if it had a DU APFSDS round. Conversely, coulda CT 40 mm cannon fulfil the 40 mm Bofors role? The Thales RapidFire is an obvious naval application of this cannon and ammunition. There is also the Oerlikon 35 mm revolver cannon. If the Navy and Army could share weapon systems, it would definitely reduce ammunition and support costs. All this talk of the 127 mm gun at £50 million a pop seems crazy. You could fit a dozen 155 mm howitzers for that kind of money. I know that the 127 mm has a highly sophisticated loading system, but if only it were less expensive.


    1. Nicholas you make some good points, in reverse order:

      1. 127mm MK45 with robotic magazine – it is eye wateringly expensive, so maybe it would be less so with the old style magazine, ammo handling arrangements. In which case the T31 looses some of the battle damage protection and other advantages, maybe sustained rate of fire. I would be OK with this. Now, stay with me here, but if T31 is our NGS go to, should we go back to Naval 155mm ? Put the gun and mechanism from the BAe Archer “pod” into a suitable turret? Still have the problem of navies not liking multi-part ammo, and lower rate of fire. However with the auto-loading mechanisms developed for land use, and the move towards a lower rate of fire of long range guided munitions (say OTO Vulcano 155), then maybe that old pipe dream would be affordable?

      2. Commonality at 40mm – I think Navy would have to conform to Army here, as the CTA 40mm is the weapon of choice for 2 “progammes of record”. However Thales does indeed have a weapons system in design if not prototyped yet.

      3. Army use of 57mm – well this one has been debated over at SNAFU blog. The Russians do apparently have a 57mm remote turret. I think it might have more use in support fires, air bursting HE, direct fire or ballastic profiles. I guess a secondary Tungsten APFSDS would deal with any non-MBT opponent – but 40mm CTA is already supposed to be able to do that. I guess I am struggling to see the “killer application” of this one. Either way I guess it would need to go into a low weight remote operated turret.


      1. The US pays about twenty five million for its Mk 45 LWG, you can see the acquisition for DDG-51 about half way down this headache inducing list of numbers:

        Click to access SCN_Book.pdf

        It would probably be a more straightforward fit without the magazine anyway, the T31’s parent class being designed for the Stanflex Mk 45.

        If you close your eyes you can see the lessons learned report busy writing itself for some war we’re yet to fight, it recognizes the general utility of the 57mm but it is critical of the use of carrier escorts to support troops ashore which diverted them from their primary role, it recommends the fitting of a large calibre gun to T31 to address this.


      2. Cta can’t really fulfill the Bofors role as it is not designed to take on anti ship missiles. Even the inclusion of starstreak may not solve this as for whatever reason the RN has backed away from this missile also it’s not even really mentioned by Thales for the naval cta 40. The Bofors is close to 2/3 times the range of CTA with CTA you are really staying in the phalanx range bracket. How much is really gained from commonality between army and navy almost no nation does it and none of them seem concerned?


  12. I have some questions regarding the MSI 30mm. They seem to be popular but are they now obsolete? The 40mm bofors can do everything the MSI mounts can but also has a anti missile/general AAW capability. As much as the MSI with Martlet looks cool is it really a good concept? There are mounts available solely for Martlet/Starstreak. Separate bofors 40mm and Martlet mounts to me offers greater capability and redundancy than the combined 30mm with Martlet. If we are going to add 40mm to the fleet is it feasible to phase out the 30mm?


    1. Your question is perfectly sensible, almost certainly the reason why 30mm will be retained is cost.

      If we could sell off our 30mm estate and replace it with 40mm that would be a major step forward in my opinion, as for martlett etc, there are plenty of systems that can provide that capability not least a rolling Rim frame and I am sure the uk can develop something.

      Liked by 1 person

      1. I would definitely like to see 40mm Bofors used more widely across the fleet. It’s a good gun. Heck, I’d like to see the Army use it too. I strongly believe that greater commonality would make sense. You just add an APFSDS round for anti-armour work. And it might be quite useful in naval applications too.

        Having said that, I see 40mm as an addition to 30mm not a replacement. The Navy’s NG 30mm Bushmaster II is an excellent cannon. It’s not an AAW cannon, but to repel fast attack craft and for GP fire support, it’s high rate of fire makes it hard to beat.


  13. I don’t see it replacing the 30mm either and infact to give proper 360 degree cover it is essential to retain. I would replace the all the 57mm in jed’s original suggestions with the 40mm bofors, except for T45 a position. 40mm should be good enough for main armament for batch 2 rivers – if we are going down the route of increasing it’s lethality, I would like to add sea spear (brimstone) to the class. As not only can it destroy FIAC but a ripple fire could also ruin a corvette or light frigates day, both hellfire and Brimstone are starting to also demonstrate an anti-aircraft capability.
    With the 30mm and martlet this would give quite a powerful vessel for little money as Brimstone could be shared with the army

    If money can be found 127mm for T31 and T45 if not then 76mm for both with the advanced ammo it should provide enough coverage for both AAW and anti-fiac over the frontal arc.


    1. I’ve been wondering the same thing as MikeO about 40mm vs 30mm. If T31 is going 57mm + 40mm that’s adding 2 new logistics lines to the RN so would there be benefit from at least looking to retire the 30mm one? As Pacman very correctly points out there is a lot of sunk cost in our 30mm estate so what would the incremental cost be of upgrading that to 40mm once potential sales of the 30mm estate were factored in (if that’s even practical) plus ongoing savings from streamlined logistics going forward? There would still be significant one-off incremental cost I imagine given how widely 30mm is deployed within the RN but with that one-off incremental cost would come increased capability.

      Most people seem to be showing Phalanx the door here so one question I have is how do 40mm and 57mm compare with Phalanx in terms of anti-ship missile capabilities? Also, is the fact that Phalanx has its own sensors something that needs to be considered? When looking at what now seems to be becoming the standard defensive fit for RFA vessels for instance, namely 2 x Phalanx (when fitted) + 2 x DS30, how much of the 40/57mm anti-air and in particular anti-missile capability is compromised if the host vessel doesn’t have a capable enough main radar? When saying dump Phalanx for 40mm is that practical on RFA vessels for instance without a main radar upgrade? (I’m just asking not arguing against by the way, I have no expertise in this area and am trying to learn.)

      If sensor issues and capability aren’t show stoppers then perhaps what MikeO was suggesting was (and this is me attempting to address Simon’s “I don’t see it replacing the 30mm either and infact to give proper 360 degree cover it is essential to retain” comment) going from the fairly standard 2 x Phalanx + 2 x DS30 defensive fit to 4 x 40mm in order to at least drive the 30mm logistics out of the system. With due acknowledgement to the transition cost and sensor issues mentioned above, as an end point that does seem more elegant in terms of a single maintenance/ammo train vs the current Phalanx+DS30 and also presumably would be quite a significant uplift in capability especially for things like the Tides, Bays and upcoming FSS not to mention QEC which would be positively bristling with 40mm if all mounts had them!

      On a final point. With the desire to see Martlet and maybe also Starstreak on a DS30 mount, if the RN were to move the Phalanx+DS30 over to an entirely 40mm setup I can’t see any reason why a side-mount couldn’t be developed to allow the 40mm mounts to host Martlet/Starstreak or is there some reason why that would be more of an issue than doing it for the 30mm mount?


  14. My comment about the 360 defence is down to the position of the 40mm turrets fore and aft. They give 360 protection but looking at the angles not necessarily close in and would potentially struggle with firing rounds at 90 degrees to the side of the ship.
    The 40mm isn’t expensive, but it’s not cheap either, therefore that is why I would retain the 30mm and LMM. The 30mm is in widespread use across the fleet and it is likely the RN has a huge stock of ammunition, to replace the 30mm on every RFA, opv, mcm with 40mm is likely to take time and be unaffordable.
    The requirement for the side mounted weapons is to backup the 40mm & cover the area before both guns crossover, therefore buying new 40mm seems excessive.
    The Phalanx is obviously still rated by the RN with planned fitment to T26 and fitting to Queen Elizabeth class it is probably just very expensive. So I can’t see it being removed from service unless it definitively proven as ineffective.

    This is another reason why I don’t like the 57mm & 40mm setup as the weapons have similar effects/tasks. Whereas the 127mm (100km +)or 76mm (39km) do bring another capability in NGS.
    To be honest I would prefer the T31 to have greater number of sea ceptor as with a little modification the missiles could give much better anti FIAC capability, otherwise potentially fit sea spear launchers to the b position & potentially the rear.

    The Americans are currently spending a lot of money on development of fancy rounds for the 57mm due to the fact it can’t kill enough FIAC with 3p alone. (The 76mm already has the DART round giving this capability). To be honest I am sceptical that any gun system could actually destroy 20- 30 FIACs quickly enough, as already mentioned alternatively fit 24 to 36 sea spear at the front and then that number of FIACs are destroyed simultaneously and instantaneously. Equally possibly the same with sea ceptor . Yes it’s more expensive to use missiles, but you’re in a 250 million pound warship with 100+ sailors surely that’s worth firing a number of 100k missiles? Plus the huge deterrence after a few firepower demonstrations, would likely mean a reduction in the FIACs being a threat. The 76mm/127mm and the 30mm would be sufficient for warning shots and any possible leakers


  15. Other options to deal with anti-ship missiles are the Oerlikon Millennium Gun, the Thales RAPIDSeaGuardian, Dragonfire, microwave weapons, an EW suite and decoys. Dragonfire may be weather dependent and may not currently be powerful enough to shoot down missiles (needs to be 300+KW AIUI), but it should be able to blind/fry a missile’s sensors. (A cheaper alternative to blind sensors might be a naval version of DIRCM? ) That said, AIUI 1+MW chemical lasers already exist that are powerful enough to shoot down missiles. Could they be fitted to any RN/RFA vessels including T31s?

    I’d like to see the T31s carry at least 24 CAMMs rather than just 12. And would it be worth fitting the Krait Defence System to the T31s to provide protection from midget subs in the Persian Gulf? Sub-hunting surface drones like Arcims or Seagull would make sense imo, especially if fitted with torpedo launchers.

    One other thing, what about firing HVPs from main naval guns to take out anti-ship missiles? A larger version of the Millennium Gun’s AHEAD round able to send out hundreds (thousands?) of tungsten projectiles into the path of a missile would be able to take out any missile, wouldn’t it? And regardless of the missile’s speed? Such a round could also be used against aircraft, UAV swarms, FIAC swarms and land targets like missile launchers.

    Something like Griffin missiles, but longer ranged, might be worth fitting to T31s to give them redundancy and the ability to take out FIACs at long range in case the Wildcat can’t take off for some reason.


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