You remembered more details of the story than me but I manged to find it... 3 years after someone else asked about it on SE: This is Randall Garrett's "Time Fu

You remembered more details of the story than me but I manged to find it... 3 years after someone else asked about it on SE: This is Randall Garrett's "Time Fuze", first published in IF, March 1954. https://scifi.stackexchange.com/questions/203584/short-story-about-the-maiden-voyage-of-an-ftl-capable-ship https://scifi.stackexchange.com/questions/203584/short-story...