Some interesting look at the Naval Guns and options for the UK's new Type 31 Frigate:

https://uklandpower.com/2019/09/19/type-31e-light-frigate-weapons-options/

https://en.wikipedia.org/wiki/Type_31_frigate

Reportedly to have a mix of 57mm and 40mm guns, which seems a bit odd caliber mix.

Also 24 AA missiles, yet no obvious provision for Anti-Ship missiles. 

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 think you are right that no formal decisions have been made.  

Budget probably does exclude the Mk45 or Mk8 guns on the Type 31.  Which is fine -- callbacks to Falklands era gunlines are just not realistic and the only other role for 5-inch now is likely to fire things like the new Hypervelocity rounds for air and missile defense, which is clearly outside the T31's mission space.  The selection of 57mm Bofors or 76mm OTO probably should come down to cost, as both are functionally interchangeable.

On the secondary guns, the current service 30mm with the possibility of adding airburst munitions (AHEAD-style) and/or Martlet seems like the most versatile option while avoiding introducing a new system.  Plenty of small-boat killing capacity without too much cost or complexity. 

And although the chap at UKLandSystems complaining about how old Phalanx is, the newer versions are almost entirely different from  the 1980s version he is familiar with, with new radars, new electronics, better guns, and much better ammo.  A Phalanx Block 1B with Surface Mode would be a fine terminal defense.  Probably to be fitted for but not with in the current budgetary environment.

76mm has more range though. On another site, when I mention 57mm, several commenters go nuts. I then get a lecture on the superiority of the OTO 76mm.

Farmplinker said:

76mm has more range though.

Not nearly as much more as some people think.  A lot of reference books are doing apples to oranges comparisons, things like maximum range versus maximum effective range (very different) or HE versus sabot rounds.  Best I can figure, the real-world difference is about 10% in favor of 76mm.  That's not much.

Whats the shell weight / HE content of 57mm vs 76mm?

2.8 kg versus 6.5 kg and 300 grams versus 650 grams. 

There are more modern rounds but actual naval SAP is relatively rare and conservative. Both are kinda useless for shooting at ships, which is why the Russians have a lightweight 100 and the French have stayed with their 100 for new designs. 

autogun said:

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?

Lets hope BAE pushes forward with the 57mm, as they also make the very promising ORKA 57mm guided shell:

BAE has also developed a new, deck mounted Missile pod, which allows missiles like the Tomahawk, Standard 3, LRASM, Naval Strike Missile etc to be easily mounted on any available deck space. Previously, these Mark41 sized missiles tubes had to be launched in a VLS cell, which the ship had to be built around.

https://www.baesystems.com/en-us/product/adaptable-deck-launcher

This would allow adding some Anti-Ship (as well as surface strike) capability to the Type 31, which it seems to currently be lacking. 

The new US FGGX  frigate will use a similar deck launcher. 

I somehow doubt that they are going to be firing Orkas at 220 rpm.... 

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!

gatnerd said:

Lets hope BAE pushes forward with the 57mm, as they also make the very promising ORKA 57mm guided shell:

Worth noting, as mentioned previously, that ORKA lost the USN's competition for a guided 57mm round in favor of the L3 ALaMO round.  I'm not sure where it stands now as a candidate for other navies, but it's probably not going to reach USN service so anyone else who wants it will probably have to pay some more development costs.  

gatnerd said:

BAE has also developed a new, deck mounted Missile pod, which allows missiles like the Tomahawk, Standard 3, LRASM, Naval Strike Missile etc to be easily mounted on any available deck space. Previously, these Mark41 sized missiles tubes had to be launched in a VLS cell, which the ship had to be built around. https://www.baesystems.com/en-us/product/adaptable-deck-launcher This would allow adding some Anti-Ship (as well as surface strike) capability to the Type 31, which it seems to currently be lacking.  The new US FGGX  frigate will use a similar deck launcher. 

It's funny to see this described as a new concept.  This same system, then called Cocoon, was offered at least 20 years ago (with the exact same picture) as a way to put Mk 41-compatible launch tubes on ships like aircraft carriers and big-deck amphibs that could not accommodate standard Mk 41s.  No takers back then, but they seem to be trying again.

The USN's new FFG(X) will NOT in fact use this type of launcher, despite BAE's advertising copy.  They will have standard Mk 41 tubes for Standard and ESSM, plus dedicated topside box launchers for NSM antiship missiles.  As a way to add antiship missiles, dedicated NSM (or Harpoon) tubes are a lot lighter and more compact.  Besides, there are no Mk-41 compatible canisters for NSM (or Harpoon) right now anyway.