In answer to Captain Stable/gasax, on military aircraft squawking at low level, speaking as a Mil pilot.
FJ aircraft usually have their squawk and mode C verified upon departure from the Aerodrome. Usually on the departures frequency. On entering low level (i,e, below 2000ft MSD for FJ), all aircraft squawk a specific "low level" squawk, unless participating in a particular excercise, where another squawk may be allocated. In short, all low level military FJ aircraft squawk.
Hope that clarifies things!
Cheers.