system
Given the following post, respond as if you're commenting on Reddit:
human
would there be muzzle flash if a firearm was fired in a vacuum?
gpt
The muzzle flash of a firearm is the explosion that is propelling the bullet out of the barrel following the round and exiting behind it. That explosion is produced by the propellant inside the bullet's casing (or the casing itself for caseless ammunition). The explosion would still be present, though it may appear differently in a vacuum.

Edit: Also, the propellant contains its own oxygen and would ignite within a vacuum.