Sorry for the late reply, she had to call Ruger directly to find out what Ruger does in cases where the entire gun needs replaced.
Directly from Ruger:
On a gun that has had work done to it Ruger puts
something on the end, or near the serial number. It is not
part of the serial number, it is merely an identifier to Ruger to show the gun had been previously worked on. In the past they have used a "U" or an "*". Since this wasn't the question I needed answered, it wasn't followed up with what Ruger's current SOP is.
If a gun needs replaced they absolutely do not under any circumstances re-stamp a serial number from an existing gun to a new, virgin frame. They will issue a brand new gun, with a brand new, never-been-used serial number, and ship it
to an FFL of the owners choosing. They do not ship a brand new gun directly to the customer. Again, this was not followed up, regarding if Ruger shipping to an FFL is required or is just a CYA move. Cursory searching appears to indicate there is a regulation within the GCA which would prevent a manufacturer from sending a
new gun directly to the customer.
Re-stamping a gun violates the GCA of '68. If Taurus, or any other manufacturer did this, they are breaking the regulations. The major manufacturers have lawyers or teams of lawyers, whose only job is to make sure the company is in compliance with Federal gun control legislation. I would wager your "original serial number" on your replacement gun has an additional mark somewhere in the serial number, maybe a -, or * or something, or they repaired your gun and sent it back to you. I strongly doubt Taurus would be unaware that issuing a duplicate serial number violates 27 C.F.R. § 478.92.
I can't think of an instance where a part of a gun would wear away the serial number as the serial numbers that matter are on the outside of the gun. Yes, I know GLOCK and other manufacturers put serial numbers other places, but it is the one on the outside of the frame that is the official serial number of record. In fact 27 C.F.R. § 478.92 requires the serial number "must be placed in a manner not susceptible of being readily obliterated, altered, or removed". So a manufacturer cannot, by law, put the serial number in a place where it could be readily obliterated by a moving part.
So I'll toss the BS flag on people receiving brand new guns with previously issued serial numbers, unless of course this happened prior to 1968, in which case there were no regulations restricting the duplication of serial numbers.
To the full auto part ... if any of my non-NFA firearms did anything other than 1 round per trigger pull, I sure as heck would not post video
evidence of me being in possession of an unregistered machine gun. ATF knows how to use the interwebs just as well, if not better, than we do.
For your reading pleasure:
§ 478.92 How must licensed manufacturers and licensed importers identify firearms, armor piercing ammunition, and large capacity ammunition feeding devices?
(a)(1) Firearms. You, as a licensed manufacturer or licensed importer of firearms, must legibly identify each firearm manufactured or imported as follows:
(i) By engraving, casting, stamping (impressing), or otherwise conspicuously placing or causing to be engraved, cast, stamped (impressed) or placed on the frame or receiver thereof an individual serial number. The serial number must be placed in a manner not susceptible of being readily obliterated, altered, or removed, and must not duplicate any serial number placed by you on any other firearm. For firearms manufactured or imported on and after January 30, 2002, the engraving, casting, or stamping (impressing) of the serial number must be to a minimum depth of .003 inch and in a print size no smaller than 1/16 inch; and
Source: Federal Firearms Regulations Reference Guide, ATF Publication 5300.4 Revised September 2005
27 C.F.R. § 478.92