Coast Guard Cutter Harriet Lane departs Coast Guard Yard in Baltimore Aug. 3, 2023, after undergoing 15 months of In-Service Vessel Sustainment Program production work. The service life extension program for this cutter entailed 113 work items, worth $21 million, which included a new electrical system and an MK38 Mod 3 gun weapon system, a first for the medium endurance cutter class. Both Coast Guard Cutters Seneca and Harriet Lane served as medium endurance cutter prototypes for new electrical and structural work and Harriet Lane served as the gun weapons systems prototype.
For more information: In-Service Vessel Sustainment Program page
Above is an announcement by the Acquisitions Directorate (CG-9). As I noted in a July post about the WMEC270 Service Life Extension program, there are still some unknowns regarding the program. The photo above may answer some of those questions.
As expected, a Mk38 gun mount has replaced the 76mm Mk75. The CG-9 post indicates the installed mount is the 25mm Mk38 Mod3, and that there is one and only one mount. The Mk92 fire control system has apparently been removed and I see no apparent new radar that would replace its air search and approach control capability. It also appears the SLQ-32 has been removed.
It appears the Mk38 Mod3 is mounted on an elevated platform about four feet above the foc’sle deck. This should provide both a better field of fire and a degree of protection from green water coming over the bow, though I felt it should have been raised a full deck.
Harriet Lane was a prototype, but it wasn’t one of the six to get the complete SLEP. They are to be Spencer, Legare, Campbell, Forward, Escanaba and Tahoma.
Harriet Lane is expected to change homeports to the Pacific and be dedicated to operations in the Western Pacific.
I think it perhaps unfortunate, that the ship that may be placed in a position where it will need to face down China Coast Guard cutters armed with 76mm guns has lost hers. Perhaps it should not matter, but it may be more difficult to act boldly when your adversary can hurt you badly, from a distance, with impunity.
Chuck Hill's CG Blog 
At least, a mk 110, 57mm.
The USCG needs to call the Navy when it needs to shoot as someone or something. All this is doing is setting up a colossal failure. Again, the USCG is trying to be something they are not intended for and it seems that nothing has changed since my tour in 75 – 79.
Nothing has changed since 1975?!? That’s the most absurd statement I’ve seen on this blog. Plenty has changed.
A) Back in the 1970s, US Coast Guard cutters used to have 76mm (3″) guns, but now they have 25mm guns.
B) A little thing called 9/11 happened — have you forgotten about 9/11 already? Telling the Coast Guard to just “call the Navy” after 9/11 is highly irresponsible.
C) Meanwhile, the Chinese Coast Guard has developed the world’s largest Coast Guard, the world’s largest maritime militia, and the world’s largest Navy in terms of numbers of ships. China also has the world’s largest Coast Guard cutters, and China’s cutters are heavily armed.
D) China has become extremely aggressive in the South China Sea, not to mention the Taiwan strait. The Chinese Coast Guard has been using its larger, more heavily armed Coast Guard cutters to bully the Coast Guards of other nations, even ramming Coast Guard ships from other nations such as the Philippines. I wonder if you’ll keep the same attitude of “Just call the Navy” after the China Coast Guard starts bullying and ramming US Coast Guard cutters.
Another thing that has changed is that the Navy is much smaller and based in far fewer places. Essentially the Navy has surface ships capable of responding in only five major ports. Norfolk/Newport News, Jacksonville, Seattle area, San Diego, and Oahu.
And they have no routine patrols off the US coast.
They can keep track of potential hostile warships and respond to them, but they are not spread around enough to respond to unconventional threats that may appear unexpected.
On the other hand there is Coast Guard in every port, and we do have the Ports, Waterways, and Coastal Security mission.