I was looking through the Cabela's Website and noticed this new safe. It looks like it operates like those bedside safes with the keypad input and would allow a person to keep a loaded carbine or shotgun loaded and out of reach of children. I have seen shotgun locks before that mount to a wall and secure the gun by the action but only work for shotguns. It looks like manufacturers are starting to now focus on how to secure long guns for ready use.
Cabela's: Sentry® Home Defense Center
ShotLock Shotgun Vault Details :: ShotLock.com
Either product would seem like a viable way to keep a loaded long gun at the ready for HD.