Firearms in Space

A Thousand Years of Quality

First of all, it's a myth that most modern guns wouldn't shoot in the vacuum of space. Although it made for a nice Firefly episode, the fact is that most all guns shoot perfectly fine in space. Do remember to have yourself tethered to something you want to go home to before firing your weapon because the bullets are like little rockets in reverse and you are the payload.
Boy-O-boy! That sounds like a real problem!
But that's not the problem.

No? What's the problem then, Chief?
The problem is long deployments in hypersleep. Is your sidearm going to be ready to go as soon as you wake up and need to put some hurt on the baddies?
To start with, you can't rely on springs. So the springs that hold the flechettes in your magazines? Those are gone from Alliance Airborne M28-G's.
Then how will my AA M28-G weapon system cycle properly?
Relax, soldier. We live in the future. We have inert silica hydraulic technology. Guaranteed to last for a thousand years in the cold dark of space (ISHT will ISHT you not!) After firing your weapon a new round is always in the chamber. And best of all — there are no user-servicable parts inside. That's right soldier, get a good night sleep because you won't be cleaning your gun at all.
So you've replaced the springs — what about the lubricants?
Regular lubricants will dry up. But organic lubricants are always working for you. They live practically forever and "feed" off the dust in the air or from the flechettes running through the weapon. And when there isn't any dust, they just rest! Quality... for a thousand years.
I noticed the AA M28-G doesn't have a velocity selector. Don't I need to worry about punching a hole in the bulkhead?
Not anymore. The barrel of your weapon recognizes what you're aiming at. A reading of soft-body targets automatically "gears down" your weapon system to a more appropriate velocity. Fire away at all the baddies without worrying about explosive decompression.
But this gun is so short — it's like you removed the butt-stock.
Recoil is a thing of the past, my good man. The flechette rounds emerge from the barrel at a very low velocity only to speed up when they get to target. More comfortable for you. Less comfortable to the baddies.