....Then, there's DDTC/ITAR, which is relevant if you manufacture ANY part for a firearm (USML) , and is required whether or not you need an FFL.
DDTC Issues Guidance on ITAR Registration | Prince Law Offices, P.C.
+1
Note that penalties are, and have been, retroactive.
Note that guidance was a long time coming, remains vague and arbitrary, and can change again, almost certainly unfavorably, not favorably.
Not that "machining" is a common hot-button, as is "add capability" and that both may become more so, yet.
Serious "show stopper" as far as most folks should be concerned.
Let a properly credentialed gunsmith do it.
He's paying more fees and f*****g with more paperwork than he should HAVE to do, but at least doesn't have to drop the entire cost of that onto just ONE customer, one instance.
Give professional gunsmiths a bit of credit for their pain. Seek out good ones. Pay their fees.
In a manner of speaking, they are "buying in bulk" on their customer's behalf.
You wouldn't pass up such a deal on gasoline, tires, steak, fresh salad greens, or roast chicken, would you?
Especially not if there were million-dollar fines and 20 year prison terms for picking the wrong side of a "bargain".
I don't LIKE that legislation or the manner in which it is applied. Neither do I f**k with it.
All pain, no gain.
And I DO like nearly every Gunsmith I've ever met, personally, and more yet whom I have never met.
So there. Easy choice.
Most especially if one buys decent firearms, doesn't BREAK shit, and doesn't kid themselves the makers were so ignorant that everything they ever made needs "modified".