How short a barrel for a compact 308 with little muzzle flash?

[Kronberg]

As I hunt during dusk and dawn even more often than in daylight, often well up in the mountains I need a rather compact and light weapon which has as little muzzleflash as possible. A sound moderator/suppressor is not legal in my country and I'm - perhaps not yet - a reloader.

What do you guys consider to be a good compromise in barrel lenght?

Thanks
Kronberg