In today’s question about firearms needing oxygen to work in space, Bricker’s answer is spot on so far as chemistry is concerned but I would be more concerned about lubrication. Even if the lube is not affected by vacuum (boiling off, for example), when it is cold* it is liable to get thick enough to gum up the works. If you try using the weapon dry with no lubricant at all, cold welding is a worry.
I read a thriller story some years ago set in balls-off-a-brass-monkey Arctica. The protagonist needed to enter a dwelling with a potential antagonist inside. He left his rifle outside but took a pistol in with him, knowing he was rendering the gun useless when it was taken back out. The warm, moist air would make dew condense on the piece, okay while inside, but it would instantly freeze outside rendering the parts immobile until he could disassemble it and scrape it all off.
*Yes, it is not cold all the time in space, but it can be.