A newly commissioned littoral combat ship was recently spotted with her crew sporting some very compact little carbines. 

Based in San Diego, the USS Mobile, an Independence-class LCS variant that only joined the fleet in 2021, earlier this month left her home port to take part in the Oceania Maritime Security Initiative. The initiative is designed to "reduce and eliminate illegal, unregulated, unreported fishing, combat transnational crimes, and enhance regional security" across the Western Pacific region. 

Embarked with the ship, besides a Navy helicopter and drone group, is a Coast Guard law enforcement detachment, or LEDET, from the Pacific Tactical Law Enforcement Team. 

Mobile recently posted some images while underway on the Initiative showing what looks to be members of her crew and the LEDET getting some range time with some noticeably short carbines. 

The guns, which look to have barrels in the 8-to-10-inch range, still feature a big A2-style front sight as well as a bayonet lug. This gives it a fairly similar look as the old (circa 2000) CQBR but with a short quad rail for accessories, or yet another variant of the vaunted Mk 18 frogman special. 

In short (see what we did there?) it looks to be an Mk18 Mod 1. 

The USCG has often used the Mk 18 in its LEDETs embarked on Navy littoral combat ships in the past, as seen in the below image and official caption. 
 

Meanwhile, in the Caribbean, another LCS, USS Milwaukee, with embarked Coast Guard LEDET 104 aboard, last month seized an estimated $27.4 million in suspected cocaine from a drug smuggling go-fast vessel at sea. We'd bet there may have been some Mk 18s involved in that as well.

For a deeper dive into the Mk 18 concept, check out the below by Jeff Gurwitch, a retired Green Beret, who has much downrange first-hand experience with the platform in Afghanistan and Iraq. Gurwitch also covers why it was (and still is) loved by many despite the loss of velocity due to its abbreviated 10.3-inch barrel. He calls it a "300-meter gun, easy," saying you can stretch out hits to 400-500 yards with it.