For photos, see this DefenseMediaNetwork post.
It looks like the Coast Guard will be getting a new gun mount soon. Defense.gov reports a new $30,556,246 contract for Mk38 Mod3 gun mounts that includes “fiscal 2015 weapons procurement (Coast Guard) funding in the amount of $5,341,232 …(and)… fiscal 2014 weapons procurement (Coast Guard) funding in the amount of $152,781“.
The announcement does not make clear how many systems this will buy. The contract also includes systems for the Navy and at least one system for the Philippines. Assuming the Philippines is buying only one system, it appears the contract will buy 16-17 systems, one for the Philippines, one for the National Guard/Reserve, three for the Coast Guard, and eleven or twelve for the Navy, but in the more likely case, the Philippines is actually buying two systems, then the numbers may actually be double this, which would make sense if the Coast Guard buy was for six Webber class. An FY2012 Contract for 21 Mk38 Mod2s for $24.2M would seem to indicate they cost about $1.1M each. I would like to think that, since the program has matured, this larger buy might actually cost less per unit, so that this is actually a buy of 30 or more systems (probably 32-34), with six going to the Coast Guard, two to the Philippines, two to the National Guard and Reserve, and the rest to the Navy.
DefenseMediaNetwork reports the Mk38 Mod3 offers a number of improvements over the Mod2 currently being fitted to the Webber class, including more ready ammunition on the mount (500 rounds vice 165), a coaxial .50 cal. gun (there was already a plan (pdf) to add a coaxial 7.62mm to the Mod2 version), higher elevation (75 degrees vice 40), better weather protection and serviceability, and the ability to simultaneously track up to three targets. There are also improvements to the search function of the ElectroOptic sensor that should make the system more useful in peacetime roles. They also report that BAE and Israeli manufacturer, Rafael, are considering adding the “Advanced Precision Kill Weapon System” APKWSII guided 70mm rocket system to the mount. In fact Israeli versions of this system already support surface to surface and surface to air missiles.
Most photos of the Mk38 Mod3, like the one above feature a 30mm gun which is an option, but it appears, from the language in the announcement, that these mounts will use the 25mm. I believe there is even a 40mm option. The Navy may be recycling existing 25mm guns, moving them to the new mount. Personally I would have preferred the larger caliber weapon, for its ability to take on larger surface targets. The 30mm would have almost as many rounds on the mount (420 vs 500), would be more accurate, have a greater effective range (3000 vs 2500 meters), and provide greater penetration.