You are correct. You cannot cut a longarm's barrel to less than 18" without creating a prohibited firearm.
But a barrel blank is not a barrel.
Barrel blanks are not made in finished lengths.
There is nothing in the CC or FA which requires a particular licence to make a gun barrel - with the exception of a 105mm or less handgun barrel.
But a barrel blank is not a barrel.
Barrel blanks are not made in finished lengths.
There is nothing in the CC or FA which requires a particular licence to make a gun barrel - with the exception of a 105mm or less handgun barrel.