I assume this is the FAQ you are referring to:
Do I have to engrave it for personal use?
"Individuals manufacturing sporting-type firearms for their own use need not hold Federal Firearms Licenses (FFLs). However, we suggest that the manufacturer at least identify the firearm with a serial number as a safeguard in the event that the firearm is lost or stolen. Also, the firearm should be identified as required in 27 CFR 478.92 if it is sold or otherwise lawfully transferred in the future."
Criminy sakes, this stuff never dies for some reason...
SHOULD =/= SHALL
This is the ATF we're talking about. That distinction is basically all they do for a living.
Of course the ATF thinks you "should" engrave the lower; they probably think you "should" pass it through a gunsmith for 'checking out' so that it gets recorded in a bound book, somewhere .
-You can make guns for your own use, provided they comply with NFA/GCA classifications (and ATF interpretations thereof ['readily convertible', 'constructive possession', 'open bolt', 'sporting purposes'] which aren't neatly posted anywhere in particular) and local laws
-You are not a manufacturer, so no marking requirements are applicable to you as the builder (you are a 'manufacturer' for the purposed of NFA Form 1 guns)
-You can rebuild destroyed foreign and machinegun parts, provided the above as well as 922r as applicable (and again, ATF interpretations thereof ['once a machinegun always a machinegun', 'modified but used for the same mechanical purpose is still a foreign-made part', etc.])
-You can sell, give away, loan, or otherwise transfer your homebrew same as any other, in accordance with NFA/local laws
-Some sellers won't let you transfer through them, out of hostile ignorance, or a desire to not have NVSN (no visible serial number) on their books
-Most torch-cut destroyed receivers can be rewelded without safety implications
-If you reweld a destroyed receiver, any intact original serial number cannot at that time be defaced (even if you have added an auxiliary number or replacement)
-A receiver cannot be destroyed with the intent of remaking it as another class of firearm; it is considered 'live' so long as the desire to reactivate remains (and yes, this is quite unprovable to any standard in court, but it's the ATF's 'reasoning')
-Drill-demilled barrels can be repaired with threaded/welded plugs and used safely (though usually not very accurately)
-Even if you build them, you may not legally repair or service your own silencer if it requires replacing parts; a new Form 1 is required for new baffles, caps, or tubes (so it is easier to destroy/replace the entire thing than have multiple legal suppressors tied together)
TCB
