"Frost and Thunder" by Randall Garrett in the anthology Time Wars as per Help Identify Viking Time Travel Short Story.
My weapon has a name now, as Sten suggested. I looked up a man who knows Norse runes, and I had another man engrave those runes on my pistol, on the right, just above the trigger.
The engraving says: Mjolnir.
Yah.
The original.
