This was taken from the DNR web site....
Handguns - Certain centerfire handguns and blackpowder handguns will be a legal method of take only during the regular gun, late muzzleloader and bonus season. Centerfire handguns, .357 caliber or larger, shooting straight wall ammunition propelling an expanding-type bullet (no full metal jacket) will be legal. Blackpowder handguns shooting a single projectile, .44 caliber or larger, will also be legal. There can be no shoulder stock or long barrel modifications to the handguns. The minimum barrel length is four inches for pistols, revolvers, and blackpowder handguns. Persons 16 years of age or less may not hunt deer with a handgun. Persons 17 through 20 years of age must be accompanied by a parent, guardian or spouse who is at least 21 years old. A person lawfully engaged in handgun hunting does not need a concealed weapons permit while they are hunting.
Transporting Handguns. Be sure to comply with the regulations regarding the transporting of handguns in motor vehicles. An unloaded handgun may be transported in a closed and fastened container or securely wrapped package which is too large to be concealed on your person, or which is not readily accessible by any passenger in the vehicle.
I'll do some checking and see if I've got an old copy of the regulations, think it use to be 6"....