Hello, please be gentle with me as i'm a newbie here..

But I have been trying for years now to find the tilte of a black and white film I watched many many years ago which featured a small boy, along with other children, who were playing in an abandoned RAF or Army station/barracks
shortly after WWII and finds a loaded revolver in an office....?
I have made myself a nusiance to all and sundry, asking if they remembered this film...but all to no avail....!
anyone out there as daft as me?
toodle pip!
Ivan.