This Day in Coast Guard History, April 30

Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

April 30

Oil painting of George Washington’s inauguration as the first President of the United States which took place on April 30, 1789. circa 1899

1789  President George Washington was inaugurated in New York City as the nation’s first President.  His inauguration marked the beginning of U.S. Constitutional government.

1798  Congress established the Department of the Navy on this date.  Nevertheless, the United States Navy traces its origins to the Continental Navy, which the Continental Congress established on October 13, 1775 by authorizing the procurement, fitting out, manning, and dispatch of two armed vessels to cruise in search of munitions ships supplying the British Army in America.  In 1972, Chief of Naval Operations Admiral Elmo R. Zumwalt authorized the recognition of 13 October 13, 1775 as the Navy’s official birthday.

1818  Congress authorized use of “land and naval forces of the United States to compel any foreign ship to depart United States in all cases in which, by the laws of nations or the treaties of the United States, they ought not to remain within the United States.”  This was the basis of neutrality enforcement.

1832  All commissions of naval officers serving in the Revenue Cutter Service were revoked.  All vacancies were then filled by promotion from within the Service for the first time.

BM1 Edgar Culbertson in the yard at the Coast Guard Lifeboat Station in Duluth, Minnesota, circa 1967

1967  BM1 Edgar A. Culbertson gave his life attempting to rescue three boys in Duluth, Minnesota.  BM1 Culbertson, along with two other members of Station Duluth, volunteered to venture out on the North Pier at Duluth to rescue three boys who had been reported to be out on the pier during a severe storm.  Witnesses had seen a wave wash one of the boys away but two were apparently trapped near the lighthouse at the end of the pier.  Culbertson’s Coast Guard Medal citation noted: “Lashing themselves together, the three men proceeded, with hand lanterns as the only illumination, to the end of the breakwater.  Despite the high waves, winds gusting to 40 knots, driving rain and 36 degree water, the rescue party diligently searched the breakwater and light but found no trace of the boys.  While returning to the beach a 20-foot wave swept Petty Officer CULBERTSON off his feet and hurled him up to and over the breakwater parapet into the sea.  Despite the strenuous efforts of his teammates, Petty Officer CULBERTSON perished in this gallant rescue attempt.”  He was posthumously awarded the Coast Guard Medal.  The other two Coast Guardsmen, BM2 Richard R. Callahan and FN Ronald C. Prei, were also awarded the Coast Guard Medal for their heroism.

The Coast Guard Cutter Edgar Culbertson sails into port in Galveston, Texas, March 23, 2020. The Edgar Culbertson is the service’s 37th fast response cutter. (U.S. Coast Guard photo by Petty Officer 3rd Class Paige Hause)

2020  The crew of the Coast Guard Cutter Midgett concluded a successful 37-day patrol in support of counter-Illegal, Unregulated and Unreported (IUU) fishing and regional security operations in Oceania, April 30, 2020. Patrolling over 7,118 square nautical miles (8,191 statute miles), Midgett’s law enforcement team boarded seven commercial foreign-flagged fishing vessels. The boardings verified compliance with WCPFC conservation management measures and specifications for the marking and identification of fishing vessels. They conducted 15 additional sightings and vessel queries. Those reports were provided to the FFA Regional Fisheries Surveillance Center in Honiara, Solomon Islands, demonstrating the Coast Guard’s interoperability with its key regional partners. The crew conducted joint operations with crews aboard an HC-130 Hercules long-range surveillance aircraft from U.S. Coast Guard Air Station Barbers Point, who flew several reconnaissance flights to improve maritime domain awareness. Midgett’s crew of 120 departed their homeport of Honolulu in late March, 2020, but returned shortly after to address concerns over possible COVID-19 exposure among the crew. One crew member who did not sail with the cutter for other reasons tested positive for the virus on April 1. Although no one else showed COVID-19 symptoms, the command, in concert with military and state health officials, took immediate and decisive action to quarantine and test those at risk of exposure. No one aboard tested positive, and the ill member ashore made a full recovery. Midgett resumed the patrol on April, 8, 2020.

The crews of the Coast Guard Cutters Midgett (WMSL 757) and Kimball (WMSL 756) transit past Koko Head on Oahu, Hawaii, Aug. 16, 2019. The Kimball and Midgett are both homeported in Honolulu and two of the newest Coast Guard cutters to join the fleet. (U.S. Coast Guard photo by Petty Officer 3rd Class Matthew West/Released)

“Coast Guard Cutter Calhoun seizes over $74 million in cocaine interdicted in Atlantic Ocean” –Damn that is a long way from home!

A Coast Guard Cutter Calhoun (WMSL 759) small boat approaches a vessel suspected of drug smuggling in the Atlantic Ocean, April 12, 2025. Calhoun crew members boarded the fishing vessel approximately 1,265 miles west of Las Palmas, Canary Islands and seized approximately 10,000 pounds of cocaine, worth an estimated $74 million. (U.S. Coast Guard photo)

Below is a news release from Coast Guard News.

Another photo of the intercepted vessel. (U.S. Coast Guard photo)

Sometimes things in a news release just jump out at you as unusual. First there were the photos of the smuggling vessel. It is a Dhow. Looks like something you might see in the Red Sea.

Then there is the location of the intercept, “1,265 miles west of Las Palmas, Canary Islands.” The Canary Islands are off the Coast of Morocco, North Africa.

Assuming the report is in nautical miles and the intercept was due West of Las Palmas, then that put the intercept about 2200 nautical miles due East of Orlando, Florida.

It is most likely the drugs were ultimately bound for Europe. This has to have been an intelligence based intercept.


April 28, 2025

Coast Guard Cutter Calhoun seizes over $74 million in cocaine interdicted in Atlantic Ocean

ATLANTIC OCEAN — The crew of U.S. Coast Guard Cutter Calhoun (WMSL 759) seized approximately 10,000 pounds of cocaine, worth an estimated $74 million in the Atlantic Ocean, April 12-13, 2025.

The seized contraband was the result of an interdiction in international waters in the Atlantic Ocean, and five suspected smugglers remain in U.S. custody pending prosecutorial disposition.

On April 12, the Calhoun, under tactical control of Coast Guard Atlantic Area, detected a suspicious fishing vessel in international waters exhibiting behavior consistent with narcotic trafficking approximately 1,265 miles west of Las Palmas, Canary Islands. Calhoun’s crew launched a cutter small boat and interdicted the suspicious vessel, apprehending five suspected smugglers and seizing approximately 10,000 pounds of cocaine.

“This interdiction demonstrates the Coast Guard’s unwavering commitment to combating transnational criminal organizations (TCOs),” said Vice Adm. Nathan Moore, commander, Coast Guard Atlantic Area. “Our dedicated crews, in close coordination with interagency and international partners, continue to disrupt the flow of illicit narcotics, which serves as a critical strategic action that disrupts the financial networks of TCOs, undermining their ability to fund further illicit activities that threaten our communities.”

The Coast Guard is the United States’ lead federal maritime law enforcement agency with authority to enforce national and international laws on the high seas and waters within U.S. jurisdiction. The Coast Guard continues increased operations to interdict, seize and disrupt transshipments of cocaine and other bulk illicit drugs by sea. These drugs fuel and enable cartels and TCOs to produce and traffic illegal fentanyl, threatening the United States.

Calhoun, which commissioned in 2024, is the newest of four, 418-foot, Legend-class national security cutters homeported in North Charleston, South Carolina. The cutter’s primary missions are counter-drug operations and defense readiness.

Calhoun falls under the command of U.S. Coast Guard Atlantic Area, which is based in Portsmouth, Virginia. U.S. Coast Guard Atlantic Area oversees all Coast Guard operations east of the Rocky Mountains to the Arabian Gulf. In addition to surge operations, they also allocate ships to deploy to the Caribbean and Eastern Pacific to combat transnational organized crime and illicit maritime activity.

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This Day in Coast Guard History, April 29

Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

April 29

The 82-foot patrol boats of Squadron One (RONONE) deploying from Subic Bay in the Philippines to the theater of operations in Vietnam. (U.S. Coast Guard)

1965  President Lyndon Johnson approved the commitment of Coast Guard forces to service in Vietnam under the Navy Department’s operational control.  The formation for service in Vietnam of Coast Guard Squadron One (RONONE) was announced.

1975  Coast Guard discontinued operations at Con Son Island LORAN Station.

USCGC STORIS moored alongside LAMUT. The 3″/50 was located in the gun tub on the O-1 deck just aft of the stack. During WWII the 180 foot buoy tenders has a similar installation. 

1992  CGC Storis‘ 3-inch/.50 caliber main battery was removed from the cutter.  It was the last 3-inch/.50 caliber gun in service aboard any U.S. warship.  The 3-inch/.50 was a dual-purpose weapon (surface and anti-aircraft) that had been in U.S. service since the 1930s.  It was shipped to Curtis Bay where is was made inoperable and then loaned to a VFW club.

2014  The Boston-based CGC Escanaba returned to its homeport after a 36-day patrol in the North Atlantic.  While out on patrol, the medium-endurance cutter focused on fisheries missions in support of Operation Atlantic Venture.  Escanaba’s crew conducted 26 law enforcement boardings during the patrol.  Crew members measured fishing gear, inspected daily catch limits and ensured that vessels’ safety gear was in good, working order.  The cutter crew also conducted 46 training evolutions with the crew of an MH-60 Jayhawk helicopter crew from Coast Guard Air Station Cape Cod.

The crew of U.S. Coast Guard Cutter Escanaba (WMEC 907) conducts small boat personnel transfers with the U.S. Coast Guard Cutter Isaac Mayo (WPC 1112), in the South Florida Straits, Feb. 26, 2024. Escanaba’s crew contributed to the interdiction and repatriation of over 100 migrants from Haiti and Cuba while patrolling the Coast Guard Seventh District’s area of responsibility. (U.S. Coast Guard photo by Seaman Laura Holguin-Rojas)

“Charting a Course” –Indo-Pacific Defense Forum / Coast Guard in the Western Pacific

The U.S. Coast Guard cutter Harriet Lane conducts a February 2024 patrol for Operation Blue Pacific, which included combating illegal fishing with local partners. SENIOR CHIEF PETTY OFFICER CHARLY TAUTFEST/U.S. COAST GUARD

The Indo-Pacific Defense Forum reports,

The United States Coast Guard has increased its international engagements throughout the Pacific in recent years. Through initiatives such as the Pacific Area Campaign Plan, the Coast Guard plays a pivotal role in advancing the White House’s Indo-Pacific Strategy and the National Maritime Domain Awareness Plan. Such efforts align with the 2050 Strategy for the Blue Pacific Continent, the long-term vision for the region developed by the 18-member Pacific Islands Forum.

Harnessing regional expertise and understanding the advantages of coordinated responses to environmental threats and illegal fishing, the Coast Guard established two key centers of expertise in Honolulu, Hawaii, in October 2023. The Indo-Pacific Marine Environmental Response Regional Activities Center (MER-RAC) and the Illegal, Unreported and Unregulated Fisheries Center of Expertise (IUUF COE) bring together Coast Guard specialists and international partners to share best practices, facilitate expert exchanges and develop collaborative strategies for addressing transnational issues.

This Day in Coast Guard History, April 28

Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

April 28

1908  The Revenue Cutter Service became the primary federal agency in charge of patrolling regattas.

USRC Seneca, 1908

1918  CGC Seneca saved 81 survivors from the torpedoed British naval sloop Cowslip while on convoy route to Gibraltar.  Cowslip had been attacked by three German U-boats.

Harry Gabriel Hamlet, USCG, Commandant of the Coast Guard (1932), commanded USS Marietta ,October 1918 – 12 July 1919

1919  While in command of USS Marietta in the Bay of Biscay, Captain Harry G. Hamlet rescued a crew of 47 persons from USS James which was sinking at sea, April 23, 1919.  For his actions that day he was awarded a Gold Lifesaving Medal.  His award citation noted: “This rescue was made extremely difficult and hazardous owing to high seas, which threatened to send the two vessels crashing together. In effecting the rescue, Captain Hamlet displayed admirable seamanship.”  Captain Hamlet would later serve as Commandant of the Coast Guard from 1932-1936. (If this story sounds familiar, it is because the same incident was erroneously reported in the “This Day in Coast Guard History, April 22 / 23.”)

Marietta (PG-15) In European waters. Photo courtesy of Paul H. Silverstone from U.S. Small Combatants: An Illustrated Design History by Norman Friedman

The U.S. Navy amphibious transport dock ship USS Cleveland (LPD-7) underway off the coast of Port Hueneme, California (USA), on 3 February 2000, in support of search and recovery operations for Alaska Airlines Flight 261.

1993  Coast Guard PACAREA LEDETs, operating from the USS Valley Forge and USS Cleveland, boarded the St. Vincent-flagged 225-foot freighter Sea Chariot about 300 miles southwest of Panama.  The boarding team discovered bales of cocaine in some of the containers on board and then seized the vessel.  The vessel was escorted through the Panama Canal to Station Miami Beach where a search of the vessel’s containers turned up 11,233 pounds of cocaine.

2001  A LEDET assigned to USS Rodney M. Davis, with later assistance from CGC Active made the largest cocaine seizure in maritime history to date when they boarded and seized the Belizean F/V Svesda Maru 1,500 miles south of San Diego.  The fishing vessel was carrying 26,931 pounds of cocaine.

Spike NLOS Missile System Photos and Video

A FaceBook friend alerted me to photos and the video above of an exercise launch of Spike NLOS missiles from a Philippine Acero class Fast Attack Craft (FAC), a version of the Israeli Shaldag V.

I see a need for something similar in the Coast Guard.

There was a discussion of Spike NLOS in earlier post. That post showed two smaller four round launchers fitted to an 11.9 meter craft.

The missile never leaves its shipping container until it is launched.

“Spike NLOS is delivered as a ‘wooden roound’ enabling long shelf life, low maintenance, and low life-cycle cost.”

TYPHOON MLS NLOS has an eight cell Spike NLOS missile launcher and integrated Toplite stabilized observation and target acquisition system (same as on the Mk38 mod2 and mod3). Photo: RAFAEL via defense-update.com

Below is one of the Philippine Acero class launching a Spike NLOS. In the US, Spike NLOS is currently used by the US Army and it is marketed through Lockheed Martin.

Philippine Navy Acero class patrol boat launches Rafael Spike NLOS. The vessel features a Rafael Typhoon MLS-NLOS missile launcher capable of carrying 8 Spike-NLOS surface-to-surface missiles (limited to 4 ships only). Additionally, it is armed with one Mk.44 Bushmaster II autocannon mounted on a Rafael Typhoon Mk 30-C remote-controlled weapon station, two M2HB Browning 12.7 mm/50-cal. heavy machine guns mounted on Rafael Mini Typhoon remote-controlled weapon stations, and two M60 7.62 mm/30-cal. GP machine guns.

Today in Coast Guard History, April 27

Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

April 27

The overcrowded decks of the paddle-wheeler Sultana just before her fiery explosion.

1865  The boilers on the 260-foot wooden-hulled steamboat Sultana exploded while the vessel was traveling on the Mississippi River near Memphis.  Sultana, although designed to carry a maximum of 376 passengers, actually embarked over 2,400, most of whom were Union prisoners of war recently released from captivity.  The explosion and consequent fire killed over 1,800 and ranks as the worst commercial maritime disaster in U.S. history.

USCGC Tampa (Coast Guard Cutter, 1912) photographed in harbor, prior to World War I. Completed in 1912 as the U.S. Revenue Cutter Miami, this ship was renamed Tampa in February 1916. On 26 September 1918, while operating in the English Channel, she was torpedoed and sunk by the German Submarine UB-91. All 131 persons on board Tampa were lost with her, the largest loss of life on any U.S. combat vessel during the First World War. U.S. Naval History and Heritage Command Photograph.

1914  USRC Miami, under the command of Captain J. H. Quinan, while on the International Ice Patrol, carried out the first trials of the new fathometer built by Submarine Signal Company in Boston.

USCG Sebago (WPG-42, later WHEC-42) as seen on 28 November 1947. She retained at least some of her original armament. Twin 5″/38 and quad 40mm guns are visible. As can be seen in the photo below, her after gun mounts and depth charges had been removed and a balloon shelter installed.

1949  When a C-47 of the Military Air Transport Service developed engine trouble and ditched near CGC Sebago on Weather Station “Dog” some 380 miles from Newfoundland, a motor self-bailing boat from the cutter immediately picked up the plane’s crew of four. Although the C-47 sank within 12 minutes, there were no injuries or casualties.

1966  After a U.S. Air Force B-57 was reported overdue the U.S. Coast Guard Eastern Area Commander commenced an intensive air search.  The two-day, large-scale, over-water search for the missing aircraft, all of which was coordinated by the Coast Guard, unfortunately yielded negative results.

1980  A Coast Guard HH-3F from AIRSTA Sitka safely rescued all 14 crewman from the F/V Cathy-R after it capsized and sank west of Cape Ommaney.

1989  President George H. W. Bush dedicated the Command, Control, Communications and Intelligence Center East, otherwise known as C3I, in south Florida.  The facility, manned by Coast Guard and Customs personnel, was designed to give law enforcement agencies instant access to air and marine smuggling information.

Coast Guard Cutter Hamilton leads the way for cutters Robert Goldman and Charles Moulthrope as they depart Puerto Rico April 1. National security cutter Hamilton is escorting the two fast response cutters (FRCs) across the Atlantic to Rota, Spain. From there, the FRCs will continue to their homeport of Manama, Bahrain. U.S. Coast Guard photo by Petty Officer 3rd Class Sydney Phoenix.

2021  CGC Hamilton transited into the Black Sea in support of NATO allies and partners.  Hamilton was the first Coast Guard cutter to enter the Black Sea since CGC Dallas (WHEC 716) did so in 2008. Hamilton’s patrol came after first escorting two Fast Response Cutters from Puerto Rico across the Atlantic on their way to service with U.S. Patrol Forces Southwest Asia. Hamilton then made two logistics visits to Rota, Spain and Naples, Italy before proceeding to the Black Sea.  Hamilton was conducting a routine deployment in the U.S. Sixth Fleet, working alongside Allies, building maritime domain awareness, and sharing best practices with partner nation navies and coast guards,” according to the Navy.

210502-G-G0108-1510 BLACK SEA (May 2, 2021) USCGC Hamilton (WMSL 753) and Georgian coast guard vessels Ochamchire (P 23) and Dioskuria (P 25) conduct underway maneuvers in the Black Sea, May 2, 2021. Hamilton is on a routine deployment in the U.S. Sixth Fleet area of operations in support of U.S. national interests and security in Europe and Africa. (U.S. Coast Guard courtesy photo)

210508-G-G0108-1205 BLACK SEA May 8, 2021, USCGC Hamilton (WMSL 753) and a Ukrainian coast guard vessel conduct underway maneuvers in the Black Sea, May 8, 2021. Hamilton is on a routine deployment in the U.S. Sixth Fleet area of operations in support of U.S. national interests and security in Europe and Africa. (U.S. Coast Guard courtesy photo)

USCGC Hamilton (WMSL-753) conducting port visit in Valletta, Malta on May 17, 2021. Coast Guard Photo

“Naval base modernization highlights growing Australia-PNG-U.S. defense cooperation” –Indo-Pacific Defense Forum

Papua New Guinea (PNG) Customs Service and U.S. Coast Guard personnel prepare to conduct fisheries boardings during bilateral patrols in PNG in March 2025. IMAGE CREDIT: PETTY OFFICER 3RD CLASS JENNIFER NILSON/U.S. COAST GUARD

Indo-Pacific Defense Forum reports,

The refurbishment of a key naval base and joint initiatives with Australia and the United States underscore Papua New Guinea’s (PNG) enhanced defense posture.

The upgrades to the PNG Defence Force’s (PNGDF) Lombrum Naval Base, which U.S. forces can access under the nations’ Defense Cooperation Agreement, are evidence of the growing ties among the three partners. Other developments include expanded military exercises and training, and a proposed defense pact between Australia and PNG that would allow each nation’s troops to serve in the other’s forces.

The increasing bilateral and trilateral engagements come amid Beijing’s push to expand its influence in the Pacific Islands.

Lombrum Naval Base. Screen grab from Google Earth.

This may not seem like it would involve the Coast Guard but it has.

The deployment followed the arrival of the U.S. Coast Guard cutter Midgett in the PNG capital, Port Moresby, under the nations’ maritime law enforcement agreement, known as a shiprider, according to the U.S. Embassy. The mission will enhance maritime security, particularly against illegal, unreported and unregulated (IUU) fishing, which is a major threat to coastal communities’ livelihoods.

The USCGC Oliver Henry (WPC 1140) crew arrives in Manus, Papua New Guinea, on Aug. 14, 2022, from Guam as part of a patrol headed south to assist partner nations in upholding and asserting their sovereignty while protecting U.S. national interests. The U.S. Coast Guard is participating with partners to support the Pacific Islands Forum Fisheries Agency-led Operation Island Chief and the larger Operation Blue Pacific through patrols in the Western Pacific in August and September 2022. (U.S. Coast Guard photo by SW3 Victor Villanueva, NMCB-FOUR)

The US shares with Papua New Guinea a desire to prevent Illegal, Unregulated, Unreported (IUU) fishing and has a history of cooperation with Papua New Guinea.

Coast Guard bases to support cutters that patrol the Western Pacific are limited to Hawaii in the central Pacific and Guam 3,434 nautical miles (6,360 km) to the West. Manus Island is 938 nautical miles (1737 km) South of Guam and 3,530 nautical miles (6,540 km) WSW of Honolulu.

Map of EEZs in the Central Pacific showing significance of Palau, Micronesia and the Marshall Islands. (© Cleo Pascal.)

The geographic names in the area are familiar to students of the Second World War in the Pacific. Manus was a major Allied supply base.

The explosion of the U.S. Navy ammunition ship USS Mount Hood (AE-11) in Seeadler Harbor, Manus, Admiralty Islands on 10 November 1944. The smoke trails are left by fragments ejected by the explosion. The cause of the explosion could not be determined.

This Day in Coast Guard History, April 26

Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

April 26

USRC HUDSON

USRC HUDSON At the Norfolk Navy Yard, Portsmouth, Virginia, 21 April 1898 being outfitted for service in the Spanish-American War, which included adding additional armament, armor plating, and a new coat of “war paint” U.S. Coast Guard History website

1898  During the Spanish-American War, cutters Morrill, Hudson (hero ship of Cardenas Bay), and Hamilton, formerly revenue cutters and recently armed for service in the so-called “Mosquito Fleet,” passed through Hampton Roads and after asking formal permission of the Commodore, proceeded to Key West.  From that point, they joined the Navy ships of the Cuban blockading fleet.

USRC MORRILL. Photographed by the Detroit Photographic Co. Library of Congress photo No. LC-D4-9016

1899  The Revenue Cutter Service signed a lease with two prominent Baltimore landowners for 36 acres of farmland surrounding Arundel Cove, Maryland. Two months later, LT John Moore, USRCS, arrived aboard the side-wheeler Colfax to establish the “Revenue Cutter Station at Curtis Bay,” today’s United States Coast Guard Yard.

USRC Mohawk

1912  President William Howard Taft boarded the USRC Mohawk on this date in 1912.  The cutter took the president from New York City’s Recreation Pier on “West 50th Street” to Governors Island and back for the funeral of MAJGEN Frederick Dent Grant, son of former President Ulysses S. Grant.

BAE Bofors 40mm Mk4 / and Palletized Weapon Systems

Naval News reports,

Following the trend of U.S. Navy ‘containerized’ solutions for various platforms, BAE Systems is pitching its Bofors 40 Mk 4 as another containerized system for counter-UAS, counter-USV, and point-defense missions. The gun was shown for the first time at Sea Air Space 2025 as part of a broader effort to introduce the gun and its ‘3P’ all-target ammunition to the U.S. audience.

The gun is certainly interesting, but we have looked at the system before. Perhaps the biggest news from the video is that the Navy is seeking palletized weapon systems. Potentially any 8×20 or 8×40 foot clear deck space could become a weapon station.

Presumably the Navy is thinking about arming merchant ships and MSC logistics ships that are currently essentially unarmed, but Coast Guard vessels may benefit as well.

The BAE Bofors 40mm Mk4 

BAE Bofors 40mm/70 mk4

The 40mm/70 has a long and successful history. The earlier 40mm/56 was the best medium caliber anti-aircraft gun of WWII. The air cooled single 40mm/56 mount was used on Coast Guard cutters post war including 125 foot Active class cutters and B-class 95 foot Cape Class patrol boats. Twin and quad water-cooled mounts were used on larger cutters e.g. 255s, 311s, 327s, and icebreakers. The US Navy moved from the 40mm to the 3″/50 at the end of WWII because it did not have room for a proximity fuse. Miniaturization now allows the 40mm to have the same sophisticated sort of 3P fuse available for the 57mm Mk110.

Other than small arms, the Coast Guard only uses weapons that are in the US Navy inventory so, unless the Navy adopts it, the following comments are just speculation. For what it is worth, I’ll offer my opinion.

Compared to the 76mm and 57mm, the 40mm has a shorter range, and no guided or extended range projectiles, as are now available for the 76mm and to a lesser extent the 57mm. For that reason, the 40mm is no substitute for the larger guns even though it does have a higher rate of fire.

The 40mm might be considered a substitute for the Phalanx CIWS. It weighs about half as much, and shoots much further. The British apparently think it can be used as a CIWS; they are putting two on each of their Type 31 frigates. The Italians used 40mm guns as their CIWS until they started using the Strales 76mm with DART ammunition in a much expanded CIWS role. The SeaRAM system should also be considered an alternative to Phalanx or the 40mm. It looks like a more likely candidate for large cutters. The 25mm Mk38 installation planned for the OPC appears to have an extremely restricted field of fire. Replacing it with the an elevated 40mm might help. SeaRAM would improve capabilities immensely.

The 40mm could be an alternative to the 25mm Mk38 mount currently on the Webber class WPCs, if the ships can take the extra 3200 pounds–guns as large as 76 are frequently seen on similar sized vessels–68% more range (13,670 yards (12,500 m) vs 7,450 yards); more than 5 times larger projectile (2.15 lbs. (0.975 kg) vs 0.406 lbs.); a 50% higher rate of fire (300 vs 200) and air bust ammunition. On the other hand we could get similar capability by adding small missiles like APKWS, Hellfire or JASM.