There are several type of Title II firearms which are sold by Class 3 SOT dealers that are restricted by the National Firearms Act.
Each state can impose additional restrictions on the sale, purchase, and transfer of Title II firearms in addition to the compliance that is required with the National Firearms Act.
In Michigan you can own the following Title II Firearms that are regulated the the National Firearms Act:
Any Other Weapon (AOW) (only some)
Destructive Devices (DD)
Short Barreled Shotguns (SBS) (See Below but Legal as of 3/28/14)
Short Barreled Rifles (SBR) (See Below but Legal as of 3/28/14)
In Michigan you cannot own the following NFA restricted items.
some AOW’s like Tasers or Stun Guns by private citizens whether or not they are class 3 items or the individual has a CCW permit
The Michigan State Police put together a legal update on SBR and SBS which describes the differences between those over 26 inches and those under 26 inches.