I'm not sure what you mean by a 'Class 3 permit'. If he holds a Federal Firearms License, he can get the necessary paperwork from the ATF to pay the Special Occupational Tax.
If he is an individual wishing to purchase a registered NFA weapon, the dealer will be able to provide the necessary forms and instructions.
The autonomic nervous system provides for involuntary muscle function - the work of breathing, digestion, and so forth. On some folks, that's a pure waste of ingenuity.