BAE Systems will deliver five Mk 45 naval gun systems to the U.S. Navy under a recently issued $70.6 million contract to upgrade existing guns to the Mod 4 configuration, increasing their firepower and extending their range.

“The Mk 45  retains its reputation as the industry standard for large-caliber naval guns, and the Mod 4 makes it adaptable to advanced munitions,” said Joseph Senftle, vice president and general manager of Weapon Systems at BAE Systems.

“We are the world leader in developing and manufacturing maritime guns and producing reliable and affordable technology that meets the warfighter’s needs today and into the future.”

The Mk 45 is the lightest, most compact, and most widely deployed 5-inch fully automatic naval gun in the world, with more than 260 deliveries to the U.S. Navy and the navies of 10 other allied nations.

According to BAE:

“The Mod 4 configuration consists of a structurally strengthened gun mount that increases firing energy by 50 percent, enabling munitions to travel faster and farther. A new fully digitized control system provides significantly greater computing power and features a touch-screen user interface.

The Mod 4 upgrade is a cost-effective solution to increase capability and adaptability for advanced munitions. The modernization of these gun systems will keep them in service for decades to come. Mk 45 guns are deployed on the Navy’s fleet of guided-missile Ticonderoga-class cruisers and Arleigh Burke-class destroyers.”

Work on the Mk 45 Mod 4 upgrades will be performed at the BAE Systems facility in Louisville, Kentucky, with support from the company’s supplier base, and is expected to be completed by the end of 2023.

0 0 vote
Article Rating
Notify of
Inline Feedbacks
View all comments

Literally more bang for your buck!


Anyone know if the type 31 is getting the mk45 gun? The guns rate of fire is lower than the British 4.5” naval gun but it carry’s bigger shells and burst charges for against aircraft ect. The RN will have a few 4.5” guns lying around in future but does it make sense saving money to put them on the 31s or just have the same 5” for all frigates, and the destroyers will still have the 4.5” gun unless they’re thinking of changing it but I doubt that, more silos would be better. And how much would it really… Read more »


In short no…

There is not enough money for it in the budget. And either way it would cost more than free…which is how much 4.5 will cost. And 4.5 isn’t leaving service any time soon as the T45 will have them until they leave service.

In fact I can’t see anything else on the T31 than a 4.5, because 57mm, 76mm or 127mm cannot compete with free…


Yeah I thought that, I did see the mk45 in type 31 images though. But like I said above we will have a few 4.5” guns lying around in future so may aswell use them even if the 5” is a better option.


To be honest we don’t know what weapons the Type 31s will have when they enter service. It’s largely been assumed they will recycle systems from the 23s (4.5 inch mount, Sea Ceptor etc) because of the budget restrictions but even that has not been confirmed. Though I expect us to recycle the 4.5 inch gun, at this rate however we could end up with super sized OPVs and no weapons. ¯\_(ツ)_/¯


So the original plan to replace the guns on T45’s with the 5” has now be scrapped? Is that purely a financial decision or is to maximise space for the extra vertical launch silos they were supposed to receive?


The original plan was to give T45 a 155mm gun. But changing the gun out now will be a long, long way down the priority list. In reality they will see out their service lives with 4.5. As to space I think they could fit a standard 5 inch gun and magazine without too many difficulties, and without impacting the area set aside for Mk.41 VLS (which lets be honest they are also never going to get). But, hypothetically, if they had the 5 inch gun that T26 is getting with the automated magazine I suspect they would need a… Read more »


The 4.5″ type 8 aka kryten will stay in service till powdered ammunition is superseded. Until the Rn adopts rail weapons i cant see the RN having a budget for anything else. The reduced risk in magazines will be the only incentive. The As90 upgrade got shelved so even nearly free doesnt happen.


It’s a shame about the new gun plan for the T45, as BAE are developing rounds for it that can be used for air-defence; useful given the limited number of missiles it carries. It seems that FFBNW operates it two ways;- (a) instead of dedicated weapons, a pool is maintained and ships are equipped from the pool on a as-needed basis (eg Phalanx) (b) as a capability that can be funded and acquired through an UOR, thus coming from The Treasury’s emergency contingency fund rather than the defence budget. The apparent original intent of it, to be fitted as part… Read more »


A 155mm mount was only ever an idea they were exploring and certainly not planned in for T45 or any other vessels in the fleet. The issues with powder handling with the separate charge bags were challenging. In the end the idea just didn’t produce a significant enough advantage over the latest variants of 127mm/5″ mounts and ammunition to justify the expenditure on what would have been a unique solution. 155mm artillery derived gun systems despite all the buzz over a decade ago have pretty much failed for various reasons. The Germans toyed with putting the PZH2000 turret on a… Read more »


The UK effort was led by BAe and was going to be based on a Mk 8 4.5 mount up gunned to 155.(!!) The feed ring was removed and it would have involved feeding the hoist directly. First hoist stroke for the shell and second hoist stroke for the charge. The naval variant would have had fixed case ammo but handling a 155 fixed brass case would have meant the rate of fire would be low…very low…if you had manual handling. If mechanical handling was used there would be a small increase in rate of fire but complexity would go… Read more »


Thanks Gunbuster, I knew that they had been looking at separate charge bags but I didn’t know they had swung to an all-up round with a brass case.

The negatives far outweigh the benefits frankly, a slow to fire unique system that offers little to no advantages over the latest 127mm/5″ mounts. The ability to use ammunition from our allies is also a significant boost to our capabilities.

Mark L

The through life cost of the Mark 8 4.5″ is high because it needs people in the magazine for manual loading – the Bofors 57mm, Oto 76mm and BAE 5″ all have automated magazines. But I expect the MoD will put much more emphasis on initial cost than through life.


It’s weird, in the commercial world spending on CAPEX is a no-brainier if it leads to a saving in OPEX. But civil servants don’t seem so savvy…

Mark M

Being ex-US Navy and seeing as i have been in mount 5-1 and 5-2 aboard the ex-USS Ticonderoga many, many times. They are both MK 45s and they also need people in the magazine, just for different operations while the gun is firing. 45 may load automatically but you still need to keep that loader fed, and it is more than a 1 or 2 man job.


What? You need people for every weapon just about. You still need to load a 57mm, a 76mm, a 4.5 and older variants of a 5″. Each weapon has a number of on mount rounds ready to fire. For a 4.5 there are up to 20 on the feed ring . Once they are gone you need to reload the feed ring or whilst its firing top up the feed ring. A 76 has a lot of rounds on mount but it also fires them very quickly and you need to keep filling the feed ring or you are going… Read more »


This video handily shows the feed ring on an OTO-76/62 Super Rapid being bombed up. Apparently the use of the OTO-76 on the Peacock class for Hong Kong Patrol was not an entirely happy one for the Royal Navy due to maintenance and mechanical issues. That being said I have a sneaking suspicion that might well be partially due to the type being unique in UK service meaning there wasn’t the base of knowledge built up to support it properly especially with crew being rotated through to the class in Hong Kong. A Matelot turns up in Hong Kong… Read more »

Mark L

The Type 26 5″ magazine will be unmanned. BAE have a data sheet describing the system but it is almost two years old. The prototype was in test then so the first ones should be in production now.
There is a sales talk showing a model on youtube

John Dapper

Kind of pathetic that a 5″ gun is now considered a “large-caliber naval gun”. I’m not saying the current 5″ isn’t a great gun, but a bigger shell does more damage. The CA-134 class had auto loading 8″ gun that would fire 10 rounds/minute and the shell weighed 5x more than a 5″.
One was mounted on DD-945 in the late 1970s. I served on several destroyers during Vietnam and the difference in damage between the 5″ and the 8″ was tremendous.


I don’t suppose we can actually manufacture anything bigger than a 40mm in the UK these days can we? Even the barrel for that might be made in France.

ade pease

Please can we just have more ships before worrying about guns. Our navy is just too small to be fit for purpose, rule britania my arse. Can we have more planes please, theyle be strapping machine guns to chipmunk trainers in a minute. Can we have a descent size army please, there’s more beurocrats working at the mod than there are personnel in the entire British army. It’s all an embarrassing joke, shame on successive governments for treating defense of the realm with such disdain.

John Agazim

What happened to the $800,000.00 per projectile munitions for the MK45?