The 1st Gen "Martian Pistol", heavily modified version of the WE X Series IPSC Airsoft Pistol, itself based on the Springfield Armory XD continues to be used by James Holden (Steven Strait), Amos Burton (Wes Chatham) and Alex Kamal (Cas Anvar) after they acquired them in Season 1. Uniformed members of the Mariner Valley Police Department (MVPD) also carry them as standard issue sidearms. In "Cibola Burn" (S4E10), rogue Martian black market dealers also carry them.
Note: In the context of the show, the weapons are stated to be "designed to fire both self-propelled rounds and traditional cartridge rounds, the rear of the barrel is vented at the back to eliminate recoil for use in zero-g situations".
The "Star Helix Pistol", which is actually a visually modified Glock 26 Advanced Airsoft pistol (a fictional variant of the Glock 26 with an accessory rail, grip extension and compensated extended barrel originally manufactured by Tokyo Marui) continues to serve as the sidearm of many individuals in the series. This includes Adolphus Murtry (Burn Gorman), Chandra Wei (Jess Salgueiro) and their Royal Charter Energy (RCE) security team, members of the OPA Navy such as Camina Drummer (Cara Gee) and Klaes Ashford (David Strathairn), officers of the United Nations Navy and Marco Inaros (Keon Alexander).
Note: In the context of the show, they are described as a "common gun made from plastic polymers so it can be 3D printed cheaply and reliably. It is designed for reliability and ease of use".
A two-tone Beretta Px4 Storm Subcompact is carried by Detective Esai Martin (Paul Schulze) in "Cibola Burn" (S4E10). It is later used by Bobbie Draper (Frankie Adams) in a shootout with rogue Martian black market operatives.
A pair of "Heavy Belter Pistols" carried by Commander Klaes Ashford (David Strathairn) in "Cibola Burn" (S4E10) are actually a modified Tippmann TIPX paintball pistols in olive green.
Modified TDI Vectors are used by a United Nations Marine Corps strike team boarding the Pizzouza in "A Shot in the Dark" (S4E07). They are fitted with flashlights, compensators and EOTech sights.
A belter on board the Pizzouza is seen using an unknown submachine gun in "A Shot in the Dark" (S4E07). It does not have a stock, and appears to have a forward grip and integrated flashlight.
The "Star Helix Long Gun", which is actually an Airsoft Umarex SL9 resembling a Heckler & Koch SL8-4 with a G36K length barrel, handguard, and various futuristic modifications is seen carried by multiple factions in the season. Royal Charter Energy (RCE) security officers under the command of Adolphus Murtry (Burn Gorman) carry United Nations variants, which are tan in colour.
A heavily modified SCAR again appears as the trademark auto-shotgun carried by Amos Burton (Wes Chatham). A magwell cover prevents the type from being identified.
The "Martian Long Gun", which is actually a slightly modified APS UAR Airsoft rifle, is carried by James Holden (Steven Strait) from "Retrograde" (S4E04) onwards. Several are also seen in the armory of the Rocinante.
The unknown rifle carried by Adolphus Murtry (Burn Gorman), the head of the Royal Charter Energy (RCE) security team stationed on New Terra/Ilus is actually a modified CSI STAR XR5 airsoft gun manufactured by CSI. The airsoft weapon is specifically designed to be a Science Fiction variant, and is described as an "Advanced Main Battle Rifle".
An unknown rifle is carried by Victor Sohiro (Dru Viergever) in "Cibola Burn" (S4E10) whilst assisting Klaes Ashford (David Strathairn). It is equipped with a drum magazine.