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I’m getting all nostalgic!
7A, Bofor, Gambo, Twin and Single 30 at some point during my time I maintained and fired all of them.
The Twin did have remote control capability wired into the mount as standard but the RN never adopted it or connected it up.
A point to note on the mounts with seats(Twin and Single 30mm). The impulse noise from the cannon is so high that all previous and current ear protection ( In ear plugs with Protectors/Attenuators over the top, an anti flash hood and then a helmet) is rendered useless and the noise the Gunner is exposed to is way above the H&S limits and cannot be mitigated or attenuated to an acceptable safe level.
The number of Gunners and Maintainers (Me included) with hearing loss (in left ears especially) is huge and was another less publicised factor in going to remote operation.
Now, with the remote mounts the hearing loss issue is thankfully going away.

Last edited 3 years ago by Gunbuster
Mike O

Say again, over! ?

John McGee

Excellent article. Many thanks. The RN also seems to be making more use of the 50cal HMG – especially on vessels deployed to the Gulf.


Do these guns provide timed air-burst?

Dogs Nads

Point detonation only. It’s not worth doing air-burst from anything under 35mm in practice (and even then its marginal). Basically the shell size below 35mm doesn’t have enough space for the fusing, sufficient explosive and shell casing to have decent fragmentation.

Realistically you need 40mm + to make it worthwhile.


One thing not covered in the article is the option to upgrade the Bushmaster II (mk44) from 30mm to 40mm (40×180) by changing a few parts. This gets you more punch than the 30mm, the needed extra size for reasonable air burst & will still fit the current turret (provided the turret can handle the extra recoil). It is also the cheapest way to upgrade the firepower of the River B2’s.


Northrop Grumman Delivering Next Generation Ammunition Capability to US Army | Northrop Grumman there is now a 30mm starburst. So could this be a cheap CIWS with some radar guidance from main radars on batch 2 etc?

Supportive Bloke

Another very well researched article.


An excellent and as usual, very informative piece.
Congratulations on the “new look” Lookout.


Excellent article. Thanks.

Green Fleet

Greetings all

The Mk.44 is a great weapon and it saddens me to see the Army not adopting it for their AFV fleet. I have spent the last 15 years working with chain guns of differing calibres and uses but they all look virtually identical on the inside.

There are some more pros and cons that I would like to add.

Firstly toxicity, all propelling gasses leave the barrel, therefore none leak back towards the crew operating the weapon, this may seem a tad soft but its a H&S nightmare.

As it was already alluded to, you can change the rate of fire of a chain gun by changing the amount of power going to the drive motor, this is a useful option when switching between ground and air targets. This can also be done with a conventional gun but its a pain in the ass to add artificial friction to the gun mechanism.

Bolt operation. Probably the greatest benefit of a chain gun is the fact it can fire both open and closed bolt. You get the benefit of open bolt operation, better cooling and rate of fire or you can switch to closed bolt operation for more accurate fire.

Clean firing. No one likes cleaning weapons and there is nothing worse than scrubbing carbon off the workings of a gun, chain guns fire very clean so a quick wipe of the gun body and your good to go.

The bad points. It was mentioned that a misfired round would simply be extracted and ejected due to not needing propellant gasses to cycle the weapon, this is a relevant point but misfires are less of a problem these days due to better ammunition manufacture. Most stoppages on automatic cannons are caused by a problem with the feed mechanism, and when a chain gun feed mechanism goes wrong, it goes very wrong.

Great article, I love the vid of a kid pointing a 30mm at some civvies.


The new Anglo-French 40mm is a technical marvel. But an utter waste of money with expensive ammunition. We should as you say just have bought something off the shelf. As with all joint ventures the French will benefit the most.

Green Fleet

The 40mm CTA is a beautiful piece of engineering, I could (and unluckily for some of my students do) talk about it for hours. It’s just the wrong tool for the job, it was selected based on bogus data and false claims, but we are stuck with it now.

Expensive is an understatement to say the least, a Rolls-Royce is expensive, CT40 APFSDS-T is positively extortionate.

We selected 120mm L-30 for Challenger 2 and paid the price in lack of ammunition commonality, we swore never again, we clearly don’t learn.


Yes. 🙂

I remember reading how the small size of the ammunition would allow much more to be carried and thinking space due to cost would never ever be a problem.

There are just so many options on the market we could have purchased. Even watching old videos of CV90 trundling around pooping of 40mm Bofors makes me tad angry as that old campaigner of gun would have been a lot better for us.

How much money could the Army have saved for its woeful vehicle programmes by being more pragmatic? (Saying that I am still trying to fathom why the refurbished Warrior needs a cannon. Why not a RWS with a HMG and / or 40mm grenade launcher and no turret?) But we buy woeful Ajax instead……….Again as I often with naval matters I look to the wonderfully conducted Australian vehicle programmes. They will probably end up buying Lynx to compliment their Boxers…

Saying all that I think the French Jaguar cavalry vehicle is a marvel. As much as I like Boxer (even though it doesn’t swim) I think Jaguar and Griffon would have been a better route for us.

Supportive Bloke

“Firstly toxicity, all propelling gasses leave the barrel, therefore none leak back towards the crew operating the weapon, this may seem a tad soft but its a H&S nightmare.”

Quite agree. That was alright in the ‘when you is young you is ‘ard’ days but the realisation is now that the combusted (and part combusted) propellants are not terribly good for you.

Modern boosted missile propellants are sometimes even less good: which is, in part, why soft launch missiles are a good idea.

Some of the early shoulder launched weapons were not nice to be around and if you were ever around a GenI missile launch it was very definitely into the citadel – it was so messy and toxic that it effectively shut down the ship.

“As it was already alluded to, you can change the rate of fire of a chain gun by changing the amount of power going to the drive motor.” Or by using stepper motors to provide a precise incrementation of drive speed.

Green Fleet

It has been a bit of a shock the the defence sector as militaries around the world start to catch up with modern H&S standards. Quite right in reference to the “ard” lads, gone are the days of returning from a battle run on the ranges with a bright red face (toxicity poisoning) black hands (cordite burns) def in one ear (blast) numb legs (vibration) and gut rot (range food).

Supportive Bloke

It doesn’t take a lot of imagination to see how that sort of thing effects operational effectiveness.


Interesting article, thank you.

Did I read that correctly, that the operational range of the Mk44 is shorter against ground targets than the Oerlinkon (10 km to 4 km)? That seems quite significant, even if it is more accurate at that range.

It’d be interesting to know what future options there may be, althoguh the absence of them in the article suggests the Navy has no published replacement plan at the moment. I would imagine an upgunning to the Bofors 40 mm might be on the cards, if it’s already to be found on the T31? Or even the CTA40, although I’ve heard that the ammunition for that is prohibitively expensive.


But it’s better ammo isn’t it, and instead of lots of rounds on target you could do the job with far less better rounds,


Yes, it certainly is supposed to be better- although not sure how much better than a 40 mm Bofors equivalent.
From UK Land Power: “It is becoming increasingly obvious that the ammunition costs of CTAS 40×255 mm cannons are all but unaffordable. A HE airburst round costs £250. An APFSDS round close to £1,000. In contrast, a 30×173 mm HE round costs less than $50 and an APFSDS round less than $150.” Just to be clear, the 30 x 173 is the Mk44 Bushmaster round. I think he might be being a tad disingenuous by comparing a 40 mm CTAS HE airburst round to a 30 mm Mk44 HE round (he doesn’t make it clear whether the 30 mm round has airburst functionality), but the cost differences are quite marked.
I don’t know how much of an issue it really is, but I understand Nic Drummond to have fairly good information.
For the record I like the CT40, and I think that commonality across as many platforms would drive costs such as the ammunition down dramatically, but unfortunately history shows that the MOD doesn’t always consider these things in quite the same way…

Last edited 3 years ago by Joe16

Even if the RN fitted ct40 weapons to all its ships, the number will still be tiny compared to the 500-odd that the army has agreed to purchase, so I would not imagine a RN purchase would drastically reduce ammo cost.

With this being a uk-French collaboration, does anybody know where the ammo is made?


Not vast quantities, admittedly- if they replaced all the 30 mm mounts then it’d be 41, for all the combat ships including the OPVs but leaving out the mine hunters (according to the table above). That’s taking into account the hulls in future service, bearing in mind the T31 replacements of the T23 GPs will have Bofors 40 mm instead. But I’d imagine they’d carry quite a lot more of the ammunition than an Ajax for each one?
Even then, you make a good point- “dramatic” reduction was maybe a bit too strong a statement from me..!


I do not know how much cta40 ammo the Ajax will carry, but nexter have offered an unmanned turret for the boxer that carries 170 rounds. In comparison the cta40 gun being installed in the French navy’s new OPV has 140 rounds ready to fire.


That’s interesting, I’d have thought they’d have carried more, even on an OPV.
Maybe that’s in the hopper on the turret mount, with more in the magazine on the OPV? I understand that some of these lighter mounts are deliberately not deck penetrating, so that they’re easier and cheaper to fit, but at a cost of access to more ready ammunition in a magazine under the deck.

Paul T

Wiki says that the CT40 Ammunition will be Manufactured at BAE’s ROF Glascoed Factory.

Green Fleet

I think the article is talking about max range the projectile will fly, not the effective range, so 10km is about right for a 30mm round.

Things get complicated when it comes to weapon ranges, max range can mean totally different things. For example, max effective range is different from max slant range and different from max templated range, it also differs wildly between natures. You also have to take into account the target, are you firing at a single helicopter or an entire trench system.


Fair points, thanks for that. It would be too much to hope for that everyone would find a way for an apples to apples comparison…!

Bloke down the pub

Perhaps any discussion of the 30mm mount should include the addition of the Martlet missile .


I believe the mount a 12.7 or 50 cal can be fitted as well would be an interesting mix to cover close in, out to 4k with 30mm 3p munitions And martlet out to 8km.


it suck how we don’t use a dual feed, we could have two different types of ammo ready to fire!! Or have more rounds before refil. Everyone always talks about the phalanx rate of fire but that means ammonia will last far less and will need reloaded. I like the look of the 40mm Bofors, with smart rounds ect,


Would there be any size/weight issues eventually replacing all of the DS-30’s with the 40mm system going on the T31?

Thought the direction of travel was commonality being king but we’re going to end up with 20mm, 30mm, 40mm, 57mm, 114mm and 127mm guns across the fleet.


Good point. After getting to the 30mm calibre , they end up with 2 different models and now 40mm is back as well. The RAF had the same multiplicity of light calibres
Repeat of the WW2 medium gun issue with a 4 in, a 4.5 in , two different 4.7 in ( 120mm) and a 5.25 in. The USN just had the 5 in, which remains the main medium caliber to this day.
The answer to every new issue seems to be a different calibre


I’d have like to have seen the RN rationalize down to 40mm, 76mm and 127mm for all roles.

Even though they’ve gone for the 57mm i’d still hope to see combinations of that and the 40mm bofors replace Phalanx and the 30mm mounts in time.


The USN did use a lot of 5″/38s but it was never that simple. By the end of the war, they were producing 5″/54s with completely different ammunition. They also used 5″/25s which used fixed vice semi-fixed ammunition. There were still 5″/51s in service and 4″/50s. There were also many 3″/50s and a few 3″/23s.


Currently the USN is down to the 5″ Mk45, 57mm Mk110, 30mm, 25mm, and 20mm Phalanx


30mm is lovely, having maintained 40mm Bofor, 20mm Oerlikon and Gambo and the Twin 30mm. But, it is better with a pannier full of LMM on the side.

Mike O

Genuine question but are these weapons now obsolete with the introduction of the 40mm CIWS?

With the 40mm able to defend against incoming missiles from my layman perspective it seems like a more versatile choice. There does not seem to be a large difference in space and weight requirements. Moving forward would it make sense to phase these out?


We have them and that makes them cheap.


Isnt CIWS a much much higher max rate of fire?
They are now at 4500 rpm but of course can still be used at low angle for small surface craft

Mike O

I am referring to the 40mm that will be introduced on the type 31.
This gun has 300rpm but programmable airburst ammunition.

X- Like I originally said would it not make sense moving forward (new build vessels) to have the 40mm system? I am not suggesting replacing all at once. Just phasing the 30mm mounts out to eventually achieve commonality with one system. It is being introduced anyway. Perhaps there is an operational reason not too.


Yes. My point is MoD recycles an awful lot. As has been highlighted above we will soon have a shocking mix of guns with a couple of mismatches. It is a mess.

As I said a couple of threads back I would like to see T45 have 4 of the Bofors mounts. One at A to replace the Mk8, two to replace the Phalanx, and one, if it could be managed on the hangar roof. I am big fan of the system.

Mike O

Your idea for type 45 makes perfect sense to me. When faced with a barrage of AShMs a strong last line of defence seems like a sensible investment. Relying on your outer layers to work perfectly every time seems optimistic.

When I look back for a historical analogy I keep thinking of kamikaze. Basically guided anti ship missiles. Then as now there was a multi layered defence. The inner layer defence was as many small (40mm ish) weapons as possible. Make them fly through a wall of projectiles and shrapnel. Technology has of course moved on but just as missiles have progressed so have fire control and ammunition types. The 40mm system seems like a good choice in combination with decoys. That is my thinking anyway.


Yes. You have your various flavours Asters, then SeaCeptors (quad packed, both variants), and then the guns plus something that gets often forgot here EW. Two 45’s at the centre of the carrier group would be the ultimate goal keepers…….


I’d like to see that too. 1x 57mm in place of the main-gun and 3x 40mm or 2 of each? Either way it’d provide great all-round defensive coverage.

Would be logical to see a gradual phasing out of the 20 and 30mm mounts to standardize with the 40 and 57mm systems for surface/air defence and 127mm for NGS.


I don’t know whether we would gain much putting a 57mm at A. Even though 57mm is much larger than 40mm it is still small small. You can end up thinking we need every ‘size’ of gun from 20mm up. Note the Italians and French saw the 76mm radar laid gun was the best option which is even bigger than 57mm. So perhaps a 76mm at A just for the extra oomph? If T45 were more ‘general purpose’ I would stick a 5in at A. But with only 6 of them they are staying in the middle of any group. It is all very complicated. 🙂


The 76mm can also utilise options like Volcano which gives you 40km range. Expensive – yes, but compared to a missile – no. Volcano is an option on both 76mm Compact (upgrade kit may be required) & Super Rapid. Normal Volcano rounds (76mm is new), include unguided, GPS guided, GPS+ RF guided & GPS + laser designated.

Phillip Johnson

I seem to recollect that the KCB 30mm round was painfully expensive compared to the chain gun round. I would assume that the Mk 1 will only be around until ammunition stocks are used up.


The 30mm Bushmaster on the DS30M can very easily be upgraded to 40mm by replacement of a few parts. That’s according to both manufacturers (gun and mount).

Of course, being larger, fewer rounds would be carried on the mount.

As hinted in other posts, programmable Bushmaster 30mm ammunition, comparable to the Bofors 3P, is being developed in the US.

Supportive Bloke

Realistically that needs twin switchable feeds.

One for dumb ammunition for swarms and the programmable for anti air and ant missile use.


Oh, that will be added later at roughly the original full cost when done as an ‘urgent requirement’. One hit from an Ansar Allah missile while in Red Sea transit will concentrate minds

David Graham

Agreed. Having lived in Yemen for 5 years [until 2008] I know how easy it would be to mount an attack on ships transiting the Bab el Mandeb. There is a usually deserted road which, handily, runs right down to the coast in the correct location.


Problem is that the 30mm round lacks space. Fine for knocking out UAV’s & the like, but a bit limited otherwise. Normal airburst 30mm already exists from the likes of Rhinemetal. The 40x180mm though would likely be a better starting point than 30×173. You would end up spending more money to develop something half as good, as against installing the upgrade kit to 40×180 & leverage the work done on BAE Bofors 40mm P3 to give you a running start. Reinventing the wheel just because you can, rarely pays off.

Also the 40×180 uses a case more like a pistol cartridge (no sholder). It looks more like a 9mm or .22 LR rimfire round than say a 7.62mm (shape wise). So space wise, it’s not as bad as you would think. Thats why so few parts need changing. ie the projectile is larger, but the case diameter not so much (may even be the same?). For the totaly confused – most centerfire rifle & fixed artillary ammo has a fat case (maximum powder) & is necked down to a smaller projectile at the pointy end (eg 7.62mm, 5.56mm etc). Most hand gun (pistol/revolver) ammo & some dual use ammo, has a case that is roughly the same diameter as the projectile (ie no sholder as no necking down). eg 9mm, .357, .38, .45, .22 rimfire etc.


Naturally I welcome the news that HMS Queen Elizabeth will receive her 30mm outfit before her first operational deployment later this year.

However, we should remember that these weapons will have no real capability to defend the ship against incoming anti-ship missiles – of either the super or new hypersonic type. Furthermore, because this ship mounts only 3×Phalanx CIWS systems (and no AAW missile system like most/all of her contemporarys do) QE is effectivly undefended from certain attack vectors – even if you consider this ageing 1970’s era CIWS system is still viable in the first place. Yes the theory is that escorts are always available but the contemporary hypersonic threat implies that the need to develop laser based defensive systems, and mount them widely in the fleet, may now be pressing.

The above (excellent) article reminds us that we sent our warships into mortal combat during 1982 with hopelessly outdated gunnery AAW defences – and payed a heavy price for that grave policy error arguably. One fears we may be making exactly the same mistake again today.

For the want of a nail …

Last edited 3 years ago by Moonstone
Mike O

Your comment is another reason why I would like to see the 30mm replaced by the new 40mm weapons. This would instantly increase CIWSs from 3 to 7 on the carriers.

MSI should be looking at ways to create CIWS instead of their traditional mounts.

Trevor H

You suggest that every ship in every navy was fully equipped with every up to date weapon.
They were not. We just happened to be the one doing the fighting.

Geoffrey Hicking

Ok, I give in. Other than getting people to join up, can anyone provide a specific example of a navy news site improving productivity of the UK workforce?


“Firing horizontally it can reach 10km”

This might lead people in error, it means firing at 45º or so to achieve max range.

In short the anti aircraft range stated is probably firing more horizontally than that one.

The chaingun range measurements are probably not like for like regarding the 30mm.


MK44 Bushmaster II 30mm, 30 x 173 cartridge ~5,190 mm3, 200 rpm, but would think as air cooled barrel max burst would be in the order of ~ 10 sec ?, before forced to stop due overheating, ~30 rounds. Understand the USN MK46 gun weapon system uses a water cooled barrel MK44 Bushmaster II 30mm

Did see mention effective range of 2 km, might be longer, for ref the 35 Millenium with its larger cartridge, 35 x 228 ~7,980 mm3, 1,000 rpm, keep out range quoted as guided range of 3.5 km, max effective range for sea skimming missiles 1.5 km.


Excellent article, many thanks.


Excellent article. No surface combatant, from OPV to CVN should go to see without at least 1 CIWS though, whether Phalanx, SeaRAM, or RAM. Just my thoughts.