Credited as a reprint from Tales to Astound You #1, which does not exist. Story is from Men's Adventures # 24, November 1953. Info culled from Atlas Tales.
In the year 2050 a prisoner reads about the invention of a time machine and so breaks jail to return to the past to rub out the one witness to his crime. However, as he attempts to assault the man, he realizes that he has been rendered intangible like a ghost so as to be unable to effect any change in the course of events.