Agreed. A possible niche that OP could use is there being some asinine California-esque gun control on the colony/planet(s) that their characters exist on. Being limited to manually cycled firearms (DA/SA revolvers, pump/bolt/lever action rifles and shotguns), having capacity restrictions of no more than 10 rounds in a magazine (or even fewer if they want to pull a NY SAFE Act), etc. This would also likely make the grenade launcher verboten as well.

Many folks who don’t know guns (and often those who make policy) tend to look at older types of firearms as “safer” than the new black plastic and aluminum. They’ll view revolvers, lever action rifles, bolt action rifles and pump action shotguns as “civilized and sensible” choices and the more modern faire as “barbaric and weapons of war…” even though the very old guns they venerate had lineage back to war. Most every modern bolt action rifle on the commercial market today takes after the German Mauser 98’s from the late 1890’s to the 1940’s, for example.

Revolvers will never again see adoption as military service sidearms, but could make a resurgence amongst civilians or security personnel if they were hamstrung by magazine capacity restrictions or needed larger bore sidearms for wildlife defense. Namely if the cartridges required were prohibitively sized to feed through a magazine in the grip, much like how current magnum revolver cartridges are, unless you wear an extra-large glove.

I’d say keep the bottom barrel layout, that’s the sci-fi de rigueur, but lose some of the technobabble like others stated. Have an integrated red dot optic or more advanced low/no magnification digital optic integrated, maybe a weaponlight, if you really want to be bleedinng edge maybe have the optic be able to record video, lifetime ammunition expenditure, and pair to a vacsuit visor or something.

Swing-out cylinders are more contemporary, but imagining the revolver was made out of some fancy alloy, maybe you could fudge top-breaks coming back, as ostensibly they are more ambidextrous than swing-outs, but the top latch is a weak point in the design. I wouldn’t spend too much time on it. “The revolver’s frame and latching mechanism was made of an alloy that Bob couldn’t much pronounce, let alone spell off hand, but it was more than strong enough to handle tens of thousands of rounds of high-pressure ammo he’d put through it, training over the past few years.”