Depends how big you are .
You don't have to get the sot to make nfa stuff just saves on tax stamps.
Sot is yearly , FFl few in every 3 or 5 I forget .
There's plenty of small FFl 07 that don't need to pay itar. Also if your selling products to customers and going to pay itar there's different amounts you'd pay depending on how much you made that year etc .
Some get a ffl07 and just sell designs to big company's to produce and sell. Allows them to build some thing fa auto , work out the bugs etc . Vs trying to do some thing only in soild works and selling that idea. Just cause it works/functions in sw doesn't mean when you build it , it will work. Also when you go from sw to making something you'll find manufacturing problems .
Dealing with first time builds at my work I see this first hand . At times before I even start making a new part I can point out manufacturing problems. So for some thing like a mg or fa. Some people get the FFl so they can build it first vs trying to sell a idea .
I forget who makes the .338 lupa gun that's like a ar10 on roids. I've talked to the guy who designed it a few times on another site . He doesn't sell weapons to people just the designs to company's . Doesn't need to pay itar on what he earns per rifke sold by the company who bought his idea.
I've been looking in to and working on getting a FFl07 for the last year . I'm at the point of getting my personal work shop rezoned vs trying to pay rent waiting for the FFl etc 
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Heck I'd give my left nut to get a 10x10 room in jacks building .
