Well, projectiles would travel somewhere between just under mach 1 and a top limit of... mach 3, maybe? So the flash would have to be some time between 1.5 and

Well, projectiles would travel somewhere between just under mach 1 and a top limit of... mach 3, maybe? So the flash would have to be some time between 1.5 and 5 seconds before the explosion? That is not a very large window.