ATF looked at Can Cannon from X Products and ruled that the Can Cannon itself is not illegal, but once it is put on a rifle receiver, it's a short barrel rifle. Furthermore, if it is placed on a pistol, it will be an AOW - Any Other Weapon.
X Products submitted their revised design.
You can read the determination letter
http://www.thefirearmblog.com/blog/wp-content/uploads/2015/09/Can_Cannon_Determination_Letter.pdf
From: The Firearm Blog
