As seen on Eros, carried by CPM employees. Substantially similar to the Star Helix pistols. Retouched screencaps after the jump:
As seen in episodes 9 & 10 of season 1. Screencaps after the jump:
More screencaps, from episodes 7 + 8. These have all been retouched, lightened, sharpened, etc, to show details, and should not be used for color-matching. 20 or so images after the jump:
The MCRN carry pistols, described thusly by signage at SDCC:
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.
Retouched screencaps through Episode 6, Rock Bottom, and the ID of the base gun, after the jump:
The ‘mystery bad guys’ seem to have at least two different firearms: a ‘grenade launcher’ and an ‘assault rifle.’ Screencaps & analysis below the jump:
In Episode 1, when the crew from the Canterbury investigate the Scopuli, they take with them at least one long gun:
The SDCC display showed a gun like this, and the signage called it a Star Helix Long Gun. It’s possible the Canterbury rifles and the Star Helix rifles are subtly different, but the screencaps as yet are not sufficient to show this.
As seen in Episode 4, the MCRN Marines carry short, bullpup rifles:
Once again, these are modified, off-the-shelf airsoft guns: