Due to recent changes in how Steam makes data available, Killing Floor 1 is no longer able to read the Dwarfs!? achievement to unlock the Killing Floor 1 achievement related to this weapon. As of this time it is not obtainable.
An Older version of this article:
To get this achievement, your Steam Community profile needs to be public. That way Killing Floor can read the Dwarfs!? achievement the next time you launch it.