There are several type of Class 3 items that are restricted by the National Firearms Act.
Each state can impose additional restrictions on the sale, purchase, and transfer of class 3 firearms in addition to the compliance that is required with the national Firearms Act.
In Indiana you can own the following items that are regulated the the National Firearms Act
Machine Guns Silencers Any Other Weapon (AOW)
Destructive Devices (DD)
Short Barreled Rifles (SBR)
In Indiana you cannot own the following NFA restricted items.
Short Barreled Shotguns (SBS) ****
NOTE: Only Only a law enforcement officer who is acting in the course of the officer’s official duties or a person who manufactures or imports for sale or sells a SBS to a law enforcement agency may possess a SBS.
Follow this link to find out more about Indiana and NFA restrictions on Class 3 Firearms