“Patria and Kongsberg Teaming Up for U.S. Turreted Mortar Programs” Defense-Aerospace

Defense-Aerospace.com reports that,

Patria and Kongsberg Defence & Aerospace have teamed up for the future U.S. turreted mortar programs.

The news here is simply that the US Army has a program to procure a turreted mortar. I don’t think the US has ever had one, at least not since the 19th century.

They offer some interesting possibilities for arming small naval craft like patrol boats. For our purposes, they are effectively low velocity short range cannon, that can fire a relatively large projectile, while requiring far less of the vessel than a typical higher velocity naval gun.

Looking specifically at the 120mm mortar, it fires a 4.7″ diameter projectile weighing about 30 pounds (I have seen weights quoted from 28 to 31 pounds. Part of the weight would be consumed propelling the projectile since this is both projectile and propellent).  That is less than half the weight of a modern 5″ projectile (70 pounds) but about five times the weight of a 57mm projectile, and the Patria turret has been mounted on some very small vessels. It has even been tested at sea in a standard sized 20 foot container.

Unguided mortar rounds tend to be less accurate than typical naval guns, but guided rounds are changing that. The Army is working on a new round.

The HEGM program objective is to create a round accurate to within one meter CEP, with dual GPS/SAL (Semi-Active Laser–Chuck) guidance to hit targets that have relocated and to function in a GPS-degraded environment.

Range is about 8,000 yards, similar to that of the Hellfire or the effective range of the 57mm Mk110 or 76mm Mk75 guns using unguided projectiles. I have seen ranges double that for smart mortar rounds. In any case, it would have sufficient range to fire from outside the effective range of likely improvised armament for a terrorist controlled vessel.

The Coast Guard is not without experience in the use of mortars on patrol boats, having mounted them on 82 foot WPBs as well as other vessels during the Vietnam era.

Gun crew on board USCGC Point Comfort (WPB-82317) firing 81mm mortar during bombardment of suspected Viet Cong staging area one mile behind An Thoi.(August 1965)

It is behind the pay wall, but the US Naval Institute Proceedings has a short argument for the Navy to look seriously at adding mortars to Its inventory of weapons. In addition to its use as a weapon, the author contends that they could be used to launch decoys or UAS. He suggests:

“The Navy could take an incremental approach to integrating mortars onto ships:

  • “Task the Naval Surface Warfare Center at Indian Head, Maryland, with testing a variety of available mortar rounds for effectiveness against maritime targets, potential for countermeasure launching, and suitability for shipboard use.
  • “Encourage the Marine Corps and the Naval Research Lab to pursue an anti-armor version of the ACERM.
  • “Fire existing Marine Corps and Army mortars from ships during a SinkEx. Assess their effectiveness on the target and their structural impact on the ship.”

This is not as good an answer to the problem of stopping larger vessels, that might be used in a terror attack, as torpedoes (probably the best solution) or missiles like Hellfire (a good solution against small vessel threats with some capability against larger vessels), but it has some capability and would also make our patrol boats more useful in the support of troops in the littorals against targets on land.

As always, this is never going to happen unless the Navy adopts the weapon. That is unlikely for the larger Navy, but the Special Warfare community might be interested.

21 thoughts on ““Patria and Kongsberg Teaming Up for U.S. Turreted Mortar Programs” Defense-Aerospace

  1. You are exactly correct. I think the NEMO could be installed on CRF boats and maybe NSWC boats. Yes SOCOM has its own unique procurement processes and DOES get boats and weapons which the blue water Navy cannot~
    Much the pity. It is so much more cost effective to upgrade and up-arm smaller vessels than buying Billion Buck warships~
    IOW we have seen the enemy and he is us!

  2. The NEMO 120mm auto Mortar would make a great fire support weapon and it doesn’t take a warship to shoot from.
    One tube on many small boats could deliver a lot from near shore. The Marines and Army have both fired old tech guns from Mike boats.
    These weapons are far more capable.
    Perhaps ideal for inshore gunnery?

  3. The NEMO 120mm would also fit very nicely in the topside weapons module of LCS, replacing one or more of the 30mm cannons.

  4. I believe that the NEMO would be very helpful in certain situations because it has a “Fear factor” that Blue Forces need in waterborne combat. Sure, a turreted mortar won’t solve all combat situations in all scenarios, but the NEMO mortar system sure beats bullets and small arms fire when something larger with more punch and destructive firepower explosives is needed.

  5. Since it’s unlikely any extra weapons will be added, the CG will be counting on the 57mm gun.

    Does the CG have any issues with it? Because it’s been ridiculed in the LCS. Is the system used to fire it the same as the LCS?

    • I am sure most people in the Coast Guard don’t have a problem with it. It is more than adequate as a signaling device–firing across the bow, which is a primary function for the Coast Guard even though that happens only very seldom.

      The system on the National Security Cutters has a better fire control system than the LCSs have. The system going on the Offshore Patrol Cutters is essentially the same as on the LCS.

      My problem with the system has been that I have doubts that it can reliably forcibly stop anything larger than a small ship.

      That is getting better with the introduction of smart ammunition, but it will still take a lot of projectiles to do the job.

      • Chuck, I think the NSC, LSC, OPC and FFGX are all converging around the same Fire Control System.

        The NSC is already there. The LCS I thought was addressing fire control as part of their lethality spiral upgrades.

      • The advantage the NSC has over the LCSs and OPCs is the SPQ-9B https://en.wikipedia.org/wiki/AN/SPQ-9

        The NSCs already have the COMBATSS-21 Mod Combat Management System (CMS) (Aegis derivative leveraging the common source library) which is on one class of LCS now (Freedom class I believe) and will also be on the FFG(X). I don’t believe it is included in the OPC.

      • @P, the article referenced regarding the 57mm Mk110 is incorrect in the statement that, ” Lightly armed with an unproven and problematic 57mm Swedish gun manufactured by Bofors, the only other foreign deployment was in Mexico’s Navy.” In fact the Bofors gun in its various forms has been around for over 50 years and it has been used by many nations including Brunei, Canada, Croatia, Finland, Germany, Indonesia, Ireland, Malaysia, Mexico, Montenegro, Singapore, Thailand and the United States. https://en.wikipedia.org/wiki/Bofors_57_mm_L%2F70_naval_artillery_gun

        The article seems to indicate the US frigate will be armed like the Italian frigate which is not the case. It will also have the 57mm. While I tend to favor the 76mm, particularly because it has a greater variety of ammunition available, the differences between the two systems is not great, particularly once the 57mm has the advantage of guided projectiles we talked about here. https://chuckhillscgblog.net/2019/11/14/guided-rounds-for-the-57mm-mk110-alamo-and-mad-fires-an-update/

        Reportedly the the 57mm is easier to maintain.

    • Hi Chuck.

      Thanks for your reply. I read your 2011 article on your study of 92 ships sunk in WW2 and if the 57mm or even 5 inch gun is adequate ( really enjoyed the detail and analysis 👍). Your concerns regarding stopping power are worrying. It sounds like every armed ship should have torpedoes, or a way to get 500kg warheads underneath the enemy ship to “crack it open”.


      This navweaps site quotes Gunners mate Robert Boyer saying the 57mm gun only needs 3 people to load and unload the gun, Vs 7 people for the 76mm gun. Imagine that’s an advantage and part of the ease of maintenance?

      One off thing I’ve noticed is the 57mm gun has a 1000 round magazine, but the 30, 40 and 76mm only have 80-120. The 5 inch has 600-680 rounds. Weird.

      Cheers mate


      • @Andrew.

        Your last paragraph is really talking about two different things. There is the total magazine capacity, the total number of rounds aboard and there is the number of rounds in the carousel that allows the gun to fire continuously without reloading. A ship with a 57mm may have 1000 rounds, but the gun only has room in its carousel for about 100 rounds, so it can only keep up its maximum rate of fire while there are rounds in the carousel. Then there has to be a crew below the gun loading additional rounds. The 76mm Mk75 had space in its carousel for 80-85 rounds, but the total magazine capacity was much greater. The 5″/38 had no carousel so it could only fire after being fully manned, but after that it could maintain up to about 20 round/min for long periods The 5″/54 Mk45 did have a carousel that contained, as I recall, 20 rounds that could be fired remotely before the upper handling room was manned.

        This has a great bearing on how much you can do before the ship completes transition from “readiness condition III” to “General Quarters.”

        What the WWII experience seems to tell us is that guns are not very good at getting a mobility kill. The Coast Guard’s peacetime missions require an ability to forcibly stop a ship of any size, that is why I am dubious about the capability of any gun system to meet that requirement.

      • But isn’t this all moot? If the 57mm cannot penetrate the hull of a standard ship, then no amount of ammo capacity would matter in a battle, just like a 9mm submachine gun cannot penetrate the armor of a tank.

        Chuck wrote many enlightening articles about up-arming Cutters to 76mm or 5-inch gun.

      • @Andrew, I do think the 57mm would be able to penetrate the hull of most ships assuming they used the delayed detonation function on the fuse, but having gotten inside it will explode, but will probably have no effect on the running a large marine diesel or even the steering gear. These components are very robust and built to stand up under a lot of strain. The projectiles we are currently using certainly will not penetrate a large marine diesel. If we are luck, they might break a fuel line, but you cannot depend on luck with an unlikely event.

      • Hi Chuck,

        Thanks for clarifying up the ready rounds vs the carousel.

        Have a good day 🙂

    • The Navy (and hence, the CG) should sell all the 57mm gun systems to an interested ally, and replace them with the Oto 76mm Rapid. There is virtually no difference between the systems, except the 76 fires a heavier shell and carries fewer total shells on mount and in magazine (given the same space, obviously). Mount weight, rate of fire, etc. are virtually identical, so all places where the 57 fits, so would the 76. The greater benefit is the 76mm’s heavier shell which offers greater penetration and heavier payload. The latter becomes very important with “smart rounds” as the projectile volume taken by sensors and electronics further reduces the explosive payload…

      As far as the mortars go, it is a horrible seapower weapon. Far too low a velocity and rate of fire. As a shore gunfire support, it’s awesome, but PBs have enough missions, so something like this mortar system should be restricted to landing craft, or a dedicated small fire support boat, like the Monitors during Vietnam. High velocity, high rate-of-fire weapons are for PBs.

  6. What’s needed is a deep penatrating round for the 57mm.

    The technology to design and produce such a round is by no means high tech.

    Compared to ALAMO or MAD-FIRES, development and procurement costs would be minimal. Training would be trivial as its just a different round for an existing, already deployed weapons system.

    Alas, the CG does not seem interested.

    They are somehow not concerned with preparing for the scenario Chuck articulates. Let’s hope that posture does not bite them in the asp.

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