[Adirondack]

Well I know there are people here more qualified to answer this than myself but if I had my choice I'd go with a good mechanical lock. At a minimum, the S&G 6730 or equivalent which would be a UL Listed group II commercial grade lock. For not much more though, a UL Listed group I lock can be had such as the S&G 8410.

A good mechanical lock will last generations and is a time proven technology. A group II lock will prevent the majority of people from entering by why of figuring out the combination but there is a select few that can figure it out in around 30 minutes believe it our not. They do this by painstakingly charting the position of the gates on the disk by the subtle feel of turning the dial slowly and feeling the fence hitting the highest disk's gate (again not many people can do it but someone with a little training and practice can.) This type of attack is particularly troublesome because the owner might not detect the theft for a long time.

On the group I mechanical locks there is an additional mechanism that holds the lever/fence away from the gates on the disks to prevent feedback from being given to an intruder by way of the dial. UL has these types of locks rated to take an expert 20 hours to open so for a gun safe in a private residence, it is pretty much impregnable by this means.