I know you were being funny...but, being picky about "official" titles is lame (vs ATF/BATF).
In letter, if you are a "firearms/related" manufacturer" you are, defacto, against the law if you make a working example of your design prior to notifying BATF of your intent. The letter of the law is so vague that that is the bottomline. Further, if you tell others (non-BATF) that this is what you are doing, you could be guilty of "conspiracy" at the discretion of BATF.
My point is that, if they wished to, the BATF could deem you a felon at their discretion for whatever you do in any kind of machinist/manufactering capacity...I'm not saying they always do it, but they "legally" can if they wish.
"Quis custodiet ipsos custodes"