Wednesday, December 19, 2018

Mk 45 5" Gun

Let’s get technical, just for a change of pace.  Let’s take a bit of a look at the standard 5” gun of the U.S. Navy.  There have been 5” guns since before WWII but we’ll limit our examination to the modern versions, the Mk 42/45.

This is a bit of a follow on to a previous post on the 5" gun - see, "Mk45 Assessment" - and offers a slightly different perspective and a few issues for consideration.

The Mk 45 was first introduced in the California (CGN-36) class in the early 1970’s and has been the US Navy’s standard 5” gun since.  Interestingly, the Navy’s last two surface warships, the LCS and the Zumwalt, have abandoned the 5” gun.

Historically, the 5” gun has proven to provide a good balance of firepower and size/weight, enabling it to be installed on a wide range of ships.  The gun has proven quite effective in supporting amphibious landings such as Normandy and the Pacific island assaults.  Stories of WWII destroyers sailing right up to the beach and providing pinpoint fire support for assault infantry are common.  

More recently, HMS Liverpool used its 4.5” gun against various Libyan ground targets in 2011, including against shore batteries firing on the British ship.  While the British 4.5” gun is not the 5” gun that is the subject of this post, it does illustrate the continued need for a naval gun of around that size.

Interestingly, all major navies seem to have settled on the 5” gun or a gun very close to that as their standard ‘heavy’ surface ship naval gun.

Here are some relevant characteristics for the Mk45 as reported by NavWeaps website (1).

  • Rate of Fire = 10-20 rpm depending on model and type of munition
  • Effective Range = 15,000 m (~9 miles) – 24,000 m (~15 miles)
  • Mount Weight = ~50,000 lbs depending on configuration
  • Train Rate = 30 deg per second
  • Fire Control = Mark 86 Gun Fire Control System or the Mark 160 Gun Computing System

Mk 45 Versions:

Mod 0 – single munition type; mechanical fuze setter
Mod 1 – selectable munition from up to six types; electronic fuze setter
Mod 2 – export version of Mod 1
Mod 3 – never produced
Mod 4 – increase to 62 caliber; strengthened supports; longer recoil stroke; stealth mount cover

Note that the mount cover is just a weather covering and provides no protection from shrapnel.  Thus, the mount is susceptible to destruction/disabling from simple shrapnel or flying debris.  Contrast this to WWII 5” mounts which had 1”-2” of armor for protection against all but a direct hit.

The Mk 45 operating crew consists of a gun captain, a panel operator and four ammunition loaders with none located in the gun mount itself.

The 5” gun was considered an anti-air mainstay weapon in WWII but modern 5” guns, while claimed by manufacturers to be anti-air capable, are not generally considered effective in the role.

Let’s consider the history of the modern 5” Mk45.  Unfortunately, there is little combat use to evaluate but here are a couple of notable instances.

Praying Mantis – In April of 1988, the Navy used 5” guns to attack Iranian oil platforms (GOSP) with mixed success – the degree of success depending on who described the action and what they felt the objectives were.

USS Merrill (DD-976, 2x 5”/54 Mk45) and USS Lynde McCormick (DDG-8, 2x 5”/54 Mk42) used air burst gunfire to suppress the Sassan oil platform personnel who refused to evacuate when warned.  Merrill destroyed a 23 mm gun that fired back.  As described by Captain Perkins, commander of SAG Bravo during Praying Mantis,

“At the first muzzle flash from the Merrill's 5-inch mount 51, the Iranian 23-mm. gun mount opened up, getting the attention of the ship's bridge and topside watchstanders. The Merrill immediately silenced the Iranian gun with a direct hit, and encountered no further opposition. After about 50 rounds had exploded over the southern half of the GOSP, a large crowd of converted martyrs gathered at the northern end. At this point, we checked fire and permitted a tug to return and pick up what appeared to be the rest of the Sassan GOSP occupants. Following this exodus, the Merrill and the Lynde McCormick alternated firing airbursts over the entire GOSP …” (2)

At the Sirri GOSP, the USS Wainwright (CG-28, 1x 5”/54 Mk42), USS Bagley (FF-1069, 1x 5”/54 Mk42), and USS Simpson (FFG-56, 1x 76 mm) exploded a compressed gas tank and set the platform ablaze.

Capt. Perkins reports that 208 rounds, total, were fired at Sassan and Sirri oil platforms.  Perkins noted that the structure of the platforms, with thin supporting legs, precluded effective naval gunfire and necessitated suppression followed by insertion of troops to destroy the platforms via demolitions.

Vincennes Incident – During the incident, the Vincennes attacked a group of possible Boghammer type speedboats but failed to record a hit despite around a hundred rounds being fired.  Initial reports indicated that two boats were sunk and a third damaged but later reports could not confirm any hits.  During the attacks, one of the 5” guns failed and the Vincennes had to maneuver to unmask the remaining gun.

Consideration of the 5” gun leads to several questions/issues:

Multiple Mounts – More guns are always better.  Guns always jam and fail – the Vincennes failure of one gun being a modern example.  If it’s worth having one gun on a ship, it’s probably worth having two or more for redundancy and reliability.  In combat, guns get damaged or destroyed and redundancy is critical.

It’s interesting to note that the Tarawa class amphibious assault ship was originally built with 3x 5” guns!

Dual Mounts – Given the scarcity of 5” mounts (one per Burke), one can’t help but wonder why dual gun mounts aren’t used to increase the ‘throw weight’.  An example of a modern dual 5” mount is the excellent Soviet AK-130 which houses two 130 mm (5.1”/70 cal) guns with a range of 23,000 m (~13 miles), a 500 round magazine (Sovremenny) and 150+ ready rounds.  In fact, the Sovremenny class carries two AK-130 mounts for a total of 4x 5” guns as compared to the Burke’s single gun.

Range – The 5” gun is the Navy’s only naval gunfire support weapon and its limited range requires close approach to shore in order to provide fire support which is at odds with the Navy’s stand-off doctrine and necessitates risking a multi-billion dollar Aegis ship.

Various extended range programs have been attempted in the past and have failed but one can’t help but wonder if a basic extended range munition/gun can’t be developed.  Previous efforts (ERGM, BTERM, and the like) have attempted to be near-magical and incorporate multi-mode guidance, advanced warhead performance, complex flight control systems, etc.  It would seem that a simple, extended range, unguided shell would be highly useful to support ground operations.  In other words, no electronics, no guidance, no advanced warhead, no flight control, no networking, none of the things that drive up costs and cause such programs to fail – just a dumb shell that travels further.

Armor – Current gun mounts are completely unprotected other than a weather cover.  As noted, WWII 5” mounts were protected by up to 2+” of armor.  Again, if a gun is worth having, it’s worth protecting it against near misses, shrapnel, and other easy kills.  This is all about keeping a ship combat-capable as long as possible in a fight.

Gunship – It might be worth considering developing a modern equivalent of the WWII Fletcher which mounted 5x 5” guns on a small hull.  With the addition of a navalized M-270 MLRS rocket launcher, one would have a compact, moderately powerful fire support vessel.

In summary, there is every reason to believe that a general purpose 5” gun is still a valuable addition to a modern warship although it should be installed in multiple, dual gun mounts to enhance its firepower and ensure its combat viability.  In addition, an extended range, unguided shell should be developed to extend the usefulness of the gun.

Note, that this is not to say that the 5" gun is the ideal naval gun.  ComNavOps is on record as preferring the 8" gun as indicated in the previous post.


(1)NavWeaps website, weapons/guns/United States of America/5"/54 (12.7 cm) Mark 45 Mods 0 – 2, retrieved 23-Sep-2017,

(2)USNI Proceedings, “Operation Praying Mantis: The Surface View”, Captain J.B. Perkins III, USN, May 1989,


  1. Do you know what kind of shore batteries the HMS Liverpool was up against? Were they ASM launchers or guns, and of what size/number? It seems like an interesting case.

    1. My understanding is it was rockets. I have not found any more specific information.

    2. If it was unguided rockets, and not missiles, it doesn't seem like that high end of a threat. I wonder if anyone's ever actually successfully engaged a warship with a BM-21.

  2. "Current gun mounts are completely unprotected other than a weather cover. As noted, WWII 5” mounts were protected by up to 2+” or armor."

    The armor protection of the 5"/38 mounts varied quite a bit. The Fletchers' Mark 30 5"/38 and the Sumner/Gearings' Mark 38 5"/38 nominally had 0.125" of armor, some sources say .25" on the frontal shield. Even the Mark 32 mounts on the cruisers only had 0.75", with perhaps a bit more on the shield. Only the battleship mounts were armored at the 2"-2.5" level.

  3. Another option to consider is a navalized version of the Marine's M777 155-mm howitzer which has a range of 30 km with the Extended Range Full Bore (EFBR) round and 40 km with the Excaliber guided round. The Army is developing a longer barreled version with a range of up to 70 km.

  4. " With the addition of a navalized M-270 MLRS rocket launcher, "

    I wonder on a ship it could have an auto loader. It would certainly add effective range and throw weight. Did the old ASROC box loader reload manually or automatically?

  5. "Armor" not the 5" gun but the USCG says the 57mm gun they are using on the Legend class has 'ballistic protection' for the gun. Kevlar? I assume they don't want a narco to shoot their gun during an arrest? BAE systems says the same thing but nothing on what that means.

  6. The navy will need smarter 5inch guns with to deal with small boat threats.

    -there may also be a need to use 5inch shells to engage UAVs that are too small,slow, and cold to reliably suck in a missile, and too far out to hit with CIWs or Bushmaster.

    Low flying helicopters may also be a hot target for 5inch guns. Again; missiles may struggle to hold lock-on if the helos are low down hugging the waves. Drop a few airburst rounds in a ballistic arc on top of them.

    Gun ammo is cheap... Provided you don't try to turn each shell into a miniturized tough-book supercomputer.

  7. In line with your gunship I would suggest a monitor; armored shallow draft with a double or triple 5" gun in a single armored turret. (The single turret making for a more compact vessel) It would fire a Salvo of MLRS then wade in closer and closer as the beach-head becomes more secure untill actually getting right next to the shore and lobbing shells even further inland or even proceeding as a Riverine asset far superior to the converted landing craft used in Vietnam. A hellfire vls could satisfy those with the precision strike obsession and for taking out armored vehicles when used as a Riverine gunboat.

    When looking at the spec's for the Zumwalt's 155 on Wikipedia I noticed the weight was 104 tons. Since a Mk45 comes in under 25 tons, an armored twin 5" would be about the same weight giving the Zumwalt 4 guns. This would provide the fire support an empty 155 won't. An MLRS unit on rails could be in the hanger instead of the chopper, sliding out to fire, then back in to reload. Combined with the Zum's range and VLS this would make it worthy of the term "cruiser" and make the 3 billion dollar boondoggle perhaps even worthy of production...maybe.

    1. " twin 5" … MLRS … VLS ... worthy of the term "cruiser"

      Your concept is decent but let's recall what a cruiser was in terms of firepower. A couple of 5" guns, some rockets, and VLS is pretty weak on a ship that size. What about taking your concept and beefing it up a bit by adding twin 8" mounts instead of 5" and eliminate the hangar/flight deck and instead devote the aft end to some combination of MLRS, land attack VLS, and anti-ship VLS? That would put your concept solidly into the cruiser category.

    2. "monitor"

      If you want to do a monitor, think big! Make it a triple 8" or 12" mount - something that could offer significant fire support.

  8. If Navy had required serious firepower they should never have cancelled the Mk71 8" / 203mm, the 240/260 lb 8" shell compares to the 70 lb 5" shell, no comparison.

    Mk 71 weight 78t including ready ammunition, range 32,000 yards/18 miles, with modern 'Bull' design shell that could be extended considerably, double?

    Instead Navy spent $Bs on the BAE Systems AGS 155mm gun & LM LRLAP shell for the Zumwalt, Navy now talking of ripping it out of the 3 Zumwalt class ships as LRLAP shell never met specs and costing ~$1M each.

  9. Five inch gun usefulness.

    All of the air defense uses could be handled by the 76mm gun with less weight, less cost and a higher rate of fire. This is exactly what the Navy did at the end of WW2.

    Swarming boats: see above.

    Shore bombardment and NGFS: The Navy has removed the 5" gun as a close support weapon by accepting thin skinned DDs that can't take a hit and are too valuable to risk. As said, a single gun cannot provide the volume of fire necessary needed to suppress evil doers.

    I have wondered why the Navy didn't consider the 6" gun for a DD sized ship after the failure of the Mk 71? Certainly an auto loading 6" gun could be made. The projectile is 110lbs, twice the weight of the 5" shell with the same range, and only one-third the recoil of the 8" gun.

    In my opinion, I would not put 5" guns on DDs or CCs. If a war devolves into a naval gun fight, our ships don't have the "toughness" (armor) to prevail. A small Fletcher sized ship with multiple 5" guns make sense. A ship with bigger guns, weather 6" or 8", makes even more sense. It's hard to overwhelm your enemy, with parity.

  10. An optionally manned ship with a couple 5in guns could sail unmanned up close to shore to draw fire and provide NSFS. Hell; make it a minesweeper while you're at it.

    Beats playing beach chicken with an AB destroyer or a hundred sailors on an LCS a single 76mm gun. (Throw one or 2 of those onboard as well.)

    1. 57mm gun on LCS. My bad, I keep underestimating just how sad those ships really are.

    2. Of all the things to criticise LCS for, the Bofors 57mm isn't one of them. It's a corvette gun for doing corvette things, with a rate of fire a hundred times higher of the 5". The things it's meant to engage with the gun - pirate skiffs, bognammers, small boats - are things that'll be just as fucked up being hit with 57mm or 127mm.

    3. "Of all the things to criticise LCS for, the Bofors 57mm isn't one of them."

      The Fletcher class destroyer was 2 ft shorter, a thousand tons lighter, and carried 5x 5" guns so, yes, I think it's fair to criticize the LCS for a single 57 mm gun as its main gun.

      Beyond that, the gun simply doesn't work. It has a systematic inaccuracy that has been documented by DOT&E and has a further inaccuracy due to vibration of the ship when at speed.

      The gun is also ineffective in the anti-swarm role for which it was intended because it has no stopping power. We've covered this extensively in past posts. Hint: dwell time.

    4. I noticed that on old promotional material for the Lockheed LCS that they gave 3 ship lengths with 3 different guns. The smallest is the existing design, the next up was a 76mm which is what Saudi Arabia is buying, and the final with the longest hull was a 5". The longer versions also all up-gunned the VLS battery. So the Navy could have had a relatively well armed corvette (albeit thin skinned) and still had room for their precious modules, and more fuel for range.

    5. @ComNavOps: Comparing a Fletcher to an LCS isn't really comparing like to like though. A Flower-class corvette would be a more appropriate comparison. :V my point was it's a corvette carrying a corvette gun that other corvettes have used. Gun-wise, it's not that worse off from other corvettes in the present day. Of course 57mm is inadequate for shore bombardment, but then you're not supposed to use corvettes for shore bombardment, not unless you're really desperate (or Malaysia. :V).

    6. " old promotional material for the Lockheed LCS"

      I'm familiar with that. It was for the original proposal to Saudi Arabia.

      Yes, the LCS could have been bigger and with more firepower, HOWEVER, it would have totally negated the original concept of an affordable, small ship that could be built in large numbers. The current cost of an LCS with all the accounting games included and a functional module is around $700M. Thus, it's reasonable to assume that the largest of the proposed LCS variants would have cost around $1.5B. We're building full size Burkes for around $1.5B - $2B so the LCS still would have represented a very poor value for the dollar.

      In other words, it would have no longer been a corvette. It would have been a thin-skinned, underarmed destroyer.

    7. "Comparing a Fletcher to an LCS isn't really comparing like to like "

      Of course it's not! It's comparing LCS crap to an excellent Fletcher. We built a ship in WWII that was the same length as the LCS, a thousand tons lighter, and gave it a mammothly larger weapons fit. We're comparing size/firepower to size/firepower and the LCS comes off horribly in the comparison. What aren't you understanding? Trying to excuse the LCS by calling it a corvette is just obfuscating.

      Even comparing the LCS to other country's corvettes results in a very bad assessment for the LCS. This isn't even debatable.

      Your attempt at a comparison of the LCS to the Flower class ignores that the LCS is around 380 ft long and 3500+ tons displacement whereas the Flower class was 205 ft and 940 tons!!!!! Talk about not comparing like and like!

      Even the Flower class had a 4" gun versus the LCS 2.2" gun!!!!! Your own - inappropriate - comparison makes clear how poor a choice the LCS 57 mm gun is.

      Far from the 57 mm gun being something not to criticize, it is one of the top items to criticize!

    8. "The current cost of an LCS with all the accounting games included and a functional module is around $700M."

      I guess that's what happens when you give the LCS essentially the same power plant as a Zumwalt.

    9. The 300t skjold class has a 76mm gun.

      Just to further illustrate that point

    10. "Far from the 57 mm gun being something not to criticize, it is one of the top items to criticize!"

      What I'm saying is to keep some perspective. Is the Bofors 57mm a weaker gun than the 5 inch? Sure. It doesn't have the lethality or the range - it's basically a direct fire weapon, an upsized Bofors 40mm. But for the things that corvettes do, comparing LCS's gun with other corvettes, it's not that badly off, given that the Bofors 57mm has been one of the most popular corvette guns in the world for the last 4 decades and change. Let's face it, nobody's going to take a corvette to get into a gun duel with the Chinese Navy (well, not unless you're Malaysia and desperate :V).

      Given the fact that there are dozens of nations using this gun who don't seem to have the problems the US has had with intergration, I submit the issue is on the US side, and not with the gun itself.

    11. You stated that the LCS 57 mm gun was not something to criticize and I demonstrated that it absolutely is since it is inaccurate and ineffective in its intended role. That's kind of the definition of something to criticize!

      Enough with this.

  11. My opinion on the choice of the 5" gun is that it was for the same reason that 120mm-125mm guns are where tanks have topped out. Its about the largest caliber where a shell can be loaded by a single individual as a single unit (the projectile and propellant are together in 1 cartridge). Consider that one of the modifications to the Mod 4 in addition to the longer barrel, was the provision for double ramming, since the ERGM was going to have to be loaded as 2 parts. To maintain the higher rates for antiair and anti-boat, you need a single load cycle. This may change as autoloading mechanisms become more common and reliable.

    Randall Rapp

    1. "Its about the largest caliber where a shell can be loaded by a single individual as a single unit"

      That's interesting. I don't know if it's true but it's interesting. We see the exact opposite with the Zumwalt (ignore the fact that the gun/ammo has been cancelled) which has 100% automation of the entire gun/ammo handling from loading-on to storage to loading of the gun. The price the Navy paid to save a few personnel was astronomical both in terms of ship's volume (the ammo handling system dominates the entire ship) and cost. Is that worth it? I doubt it.

      The middle road is the large caliber guns of WWII which used a combination of man-loading and machine-loading.

      Unfortunately, the Navy's quest today is minimal manning which has lead, and continues to lead, to some very bad decisions.

    2. A 5 inch shell weighs 70lbs

      There a very limited number of times a person can lift and load a 70lb shell.

      In any sort of burst or sustained fire, you need a lot of bodies or a lot of machinery

  12. The lack of commonality between naval and land guns always surprises me. While there are obviously corrosion and stabilisation issues, these can be overcome and commonality with land guns would dramatically reduce the ammunition cost. Stick a gyro-stabilised platform on a LCS and weld a M109A6 to it!

  13. The RArefaction waVE gunN (RAVEN) program technology could also be applied to a 155mm naval gun, the Mk 71 8 inch gun, or a new build 16 inch naval gun. "50% cannon weight reduction, 40% reduction in barrel heating, and 80% recoil reduction compared to current
    weapon systems" would allow for larger caliber gun systems to be placed on smaller ships.

    1. The problem is that These guns basically are an advanced version of a recoilless rifle with the same backblast, loading, and specialized ammunition problems. I really don't want to think about the kind of backblast you'd get from a 16" gun.

      Randall Rapp

  14. My current favorite "large gun/small boat" is the Patria NEMO on a riverine boat. It is a mortar but still cool.
    Imagine a mothership tending a bunch of ships like this but with 155mm guns.

  15. I totally feel the 8in gun needs to be resurrected... But I wouldnt put it on a Burke... The extra weight and strengthening needed to use it is just more complication to an already crowded hull that should be AAW focused and already isnt getting the AMDR the Navy wants... But for a "gun" ship...sure!!!

  16. Does anyone know how long the Mk 45 can fire at 15 rounds per minute until it has to take a break and let the barrel cool off? I recall seeing something on the 76mm gun that said around 120 rounds in rapid succession requires half an hour after to let the barrel cool. It fires 5-10 times faster than the 5 inch, but I would still think barrel temp can become an issue.

    1. As a rule, guns with an anti missile role are built lightly, especially in the barrel, to maximise rate of traverse.

      Guns without an anti missile function can be built heavier and more heat resistant.

      The UKs 4.45" naval gun had fairly poor sustained fire rate for that reason,

      Both the 76 and 5" are water cooled, but that doesn't necessarily tell us they're completely water cooled, the barrel could be cooled in one, and just the breach in another.

    2. No idea. NavWeaps site lists a barrel wear of several thousand rounds but makes no mention of heat issues. I've never heard of any overheat issue.

    3. Thanks Domo. That is helpful. I know with both tanks and artillery it is a consideration when firing rapidly.

    4. Gun heat;

      According to the Federation of American Scientists, a sustained rate of 20 rpm can be achieved with the 5"/54. This is from 1998 and may not be valid in the 5"/62, but it does give us a reference point.

    5. Why not build a ship.with the capability of an Adams class ddg ad far as guns are concerned 2 5" 54 guns with VlS tubed would solve dome of the shore bombardment questions and anti ship.needs for long range develope a 5" RAP round with no fancy electronic inv

    6. "2 5" 54 guns with VlS"

      Well, we do have the Ticonderoga class with 2x 5" guns and VLS but we only have a limited number of them and the Navy is looking to retire them as quickly as possible.


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