Ackshually, when the NFA was passed to 'tax' explosives ('destructive devices'), it was considered unconstitutional infringement on the right to keep/bear arms to ban explosives, machine guns, etc so they 'taxed' them instead. You can still buy/manufacture them with a tax stamp.

Also when congress de-funded (outlawed) the process for felons to restore their firearm rights, they forgot to do it with explosives. So even a felon can have high-energy explosives legally.