Again, since the serial-numbered component is the weapon in the eyes of the law, this would actually be the upper receiver on a SCAR (or FN/FAL, for that matter), and not the composite trigger group housing.
AC
AC
A few months ago I would have agreed with you. 
Todd squared me away and shared this link from the ATF’s FAQ section:
Here are the highlights:
Q: What is the registered part of a Short Barreled Rifle (SBR) or Short Barreled Shotgun (SBS)?
While a receiver alone may be classified as a “firearm” under the Gun Control Act (GCA), SBRs and SBSs are classified in totality under the National Firearms Act (NFA). A firearm that meets the definition of a SBR consists of a rifle that has a barrel less than 16 inches in length. A SBS consists of a shotgun that has a barrel less than 18 inches in length. The serialized receiver is recorded for registration in the National Firearms Registration and Transfer Record (NFRTR).
Q: I possess a properly registered SBR or SBS. I intend to strip the receiver and remove the barrel prior to selling the receiver. Is the bare receiver still subject to regulation under the NFA as a SBR or SBS?
A stripped receiver without a barrel does not meet the definition of a SBR or SBS under the NFA. Although the previously registered firearm would remain registered unless the possessor notified the NFA Branch of the change, there is no provision in statute or regulation requiring registration of a firearm without a barrel because its physical characteristics would make it only a GCA “firearm” pursuant to 18 U.S.C. § 921(a)(3)(B). If the subsequent owner buys the receiver as a GCA firearm and installs a barrel less than 16 inches in length (SBR) or 18 inches in length (SBS), the firearm would be subject to a $200 making tax and registration under the NFA by the manufacturer or maker of the SBR or SBS. Because registration depends upon the stated intent of the applicant, there is no provision to allow registration of a NFA firearm by anyone other than the maker or manufacturer.
Q: If I remove the short barrel from the registered SBR or SBS, is the receiver still subject to NFA transfer and possession regulations?
If the possessor retains control over the barrel or other parts required to assemble the SBR or SBS, the firearm would still be subject to NFA transfer and possession regulations. ATF recommends contacting State law enforcement officials to ensure compliance with state and local law.
Q: Does the installation of a barrel over 16 inches in length (SBR) or 18 inches in length (SBS) remove the firearm from the purview of the NFA? If so, is this considered a permanent change?
Installation of a barrel greater than 16 inches in length (SBR) or 18 inches in length (SBS) will remove the firearm from the purview of the NFA provided the registrant does not maintain control over the parts necessary to reconfigure the firearm as a SBR or SBS.
I had the Once a Machine Gun always a machine gun thing in my head and thought it was the same with a SBS and SBR. It is not.
Still taking the time to digest your previous post, but you are tracking 100% correctly on my logical thought process to this point.
ETA: My most significant concern here would be this matter of “retaining control over the barrel or other parts required to assemble …” Because of the way that this is worded, merely having a spare NFA-length upper in the house would seem to hold the weapon in an NFA status, even if that upper were intended for use on one of your other registered SBRs. Put another way, if you had a 16" barrel mounted on a registered SBR lower, and a sub-16" upper accessible elsewhere, you would technically still be in possession of an SBR in the eyes of the law, no? In this situation, the actual configuration of the weapon would continue to take a back seat to the receiver registration, because the SBR barrel assembly remained “under your control.”
What a mess.
AC
No need to mess with that pricey lower.
I’m starting to think that I just need to unload the stupid thing, and wait for KAC to sell me an E3-based SBR.
AC
My thought process was going out of state and did not get ATF approval prior to the training I would leave my SBR upper at home and soap a 16" upper on my gun for the trip. Im good to go because the upper is at home in a different state. Also say your in an NFA friendly state and have to move temporarily to a non friendly state. Leave your shorty upper secure in the origional state and put a 16" upper on your lower.
Also my PD has two 870’s we did paperwork on to SBS them. To sell them we just remove the 14" bbls and were good to go. I would also write a letter to ATF to remove them from the registry just to make life easier for the future owners.
How does it work if traveling to a state that allows SBR’s like NC coming from another state that allows them Pa?
My question is… It it a problem for me to have a SBR in Pa and then travel to NC for a class at Blackwater? Or is it to big of a PITA to do so?
I was really hoping to have all this squared away before the Vickers HD class in Nov and hopefully by June for Advanced Pistol/Carbine…
This stuff is far to f-ing complicated for the average human.:rolleyes:
AC, if you want to take a collectible lower and register it, you can do so. You can easily de-register it. My reading of the law is that you can put the engraving anywhere on the barrel or receiver (upper or lower) you want. I would engrave the upper if you intend to use a rail that will cover the entire barrel and do not want to mar a collectible lower.
The lower has the serial number. The serial number is what identifies the gun in the BATFE registry. However, the registration is not what makes the weapon an SBR. Only a short barrel makes it an SBR. Take the barrel off and throw it away, and it is no longer a short barrelled rifle, even though it is registered. If you will retain the short upper (“retaining control” over it) and no longer want the lower registered as an SBR, BATFE will remove if from the registry if you write them a letter requesting this. You had better then put a 16" barrelled upper on the rifle pretty quickly.
Many of the problems people have with the NFA today stem from the fact that it was not drafted with modular weapons in mind. If you think of your SBR as a permanently configured complete rifle instead of a lower with multiple uppers you can attach to it, your life will be much easier. Match a lower with an upper configured the way you want it, don’t monkey with it, and move on down the road.
PITA. BATFE has a specific form you can fill out to temporarily move the SBR from one state to another. I would only do this if I was taking an SBR from one SBR friendly state (Texas) to an adjoining state (Oklahoma). Every state has its own SBR laws, and you’ll be travelling over or through a bunch of them to get from PA to NC. That’s a lot of different jurisdictions you need to worry about. You’ll have to do a lot of research and possibly contact the BATFE to figure out the proper process for doing what you want to do. Why bother? Just take a regular rifle.
+1.
Why not just ship the short barreled upper to your destination and travel with the lower only (or with a non-NFA upper). Based on the logic that it is only a SBR if it is configured that way then this would avoid any problems.
Am I correct in my reasoning?
Buckaroo
No. I would not do that. What you are doing is taking an SBR in one state and moving its component parts by various means into another state for reassembly. That constitutes moving the SBR in interstate commerce without written permission of the BATFE, and that is a bad thing. Temporarily taking the upper off of the lower does not necessarily mean that the SBR is not an SBR anymore. This is simply an area we don’t have much guidance on. For more interstate transit information, look at the ATF opinion letter in this thread.
There is always a problem applying logic to laws and regulations that were poorly drafted by non-experts, somewhat internally inconsistent, not written with modern technology in mind, open to interpretation by cops, federal agent, or prosecutors in the absence of guiding case law, and continuously changed by regulatory fiat. In that situation, thinking up creative ways to achieve goals of dubious value is just wasting time at best and can get you in big, big trouble at worst. Unless you want to be a test case, discretion is the better part of valor here.
You can’t move or have the SBR in another state without an approved ATF Form 5320.20
http://www.atf.gov/forms/download/atf-f-5320-20.pdf
For the SCAR you can mark the upper or the barrel.
Sorry, I did not mean that one could fail to inform the BATFE only that shipping the upper would avoid transporting it through states that might be a problem.
Buckaroo
He would be good to go with the travel letter. It sounded like he wanted to avoid driving from state to state with an SBR in his vehicle.
Gotcha - sorry for the misread. I don’t know the answer to your question. If the ATF signed off on the move you still have to deal with state and local laws which may have definitions of “firearm” or “short barrelled rifle” that are different than either the GCA or NFA. Still a PITA.
I would much rather just take a non-NFA rifle with me if I went to a class out of state.
I just recived a response from LMT they will not take one of their rifle lowers backand SBR it. It is nice to know Noveske and DD will.
I’m not sure that NRW and DD really want this to be common knowledge in the sense that providing the service is kind of a distraction, and surely not a primary focus of either business, but both companies have proven flexible and accomodating in the past.
I believe there are still some restrictions in play about who is physically “building up” the receiver to a given degree or percentage of completion (80% comes to mind) though, so the best way to do this is to buy or send them one of their receivers and pay to have it completed – or mostly completed – for reentry onto their books as an NFA item. Again, this is a by-exception process, but one worth knowing about for customers of those particular companies … like the two of us. 
AC
And that’s my cunning plan. Buy a 12.5" upper with a Switchblock and a lower at the same time from John Noveske. The slight additional wait time is worth it for their product.
I agree it is probably a PITA to a certain degree. It came up in a few previous threads because of the questions about selling a stripped lower or complete lower as a factoy registered SBR.
I bought a complete lower this way and was interested in buying a stripped DD SBR lower to just put away for now. It turns out the deal never happened. This is when I reached out to DD and found out they would do it if I bought an SBR upper from them and they attached it to their lower. Im not sure we will see SBR lowers sold anymore. 
I liked the idea of buying things as I could afford them. I could also see a day when things are further restricted and having been too young to buy machine guns when they were affordable I would like to buy SBRs now.