Gyro matey,
I would suggest that if you don't wish to be regrettably schwacked by an unsuspecting GR/TmkSomething a wise man would do well to fly at/above 1000ft AGL, thus avoiding the vast majority of low flying military aircraft, bearing in mind that most of them don't have a radar capable of seeing you in the first place, even if they were paying attention to it at 250'!