Thanks for the link. I read it. First time I've seen an actual case of possession on having ll the parts to make an NFA weapon. But the court's opinion was based on the possession of a complete upper, a complete lower (even though they weren't assembled) and the speed at which the owner could assemble a working SBR. The OP was asking about a barrel not a complete upper (I misquoted this in my previous post). Could it still be argued he intended to make an SBR? Maybe, but it would require tools, knowledge and time. The situation in the court case linked to is not the same as the OPs situation. Complete upper vs a lone barrel.
The plaintiff argued the upper was just parts but it was fully assembled. The court opinion does seem to (possibly) support the court may have considered this argument if the upper was not assembled and the barrel was just a part in a junk box of parts. Another, albeit weaker argument is the court ruling applied to this case not all cases. Probably will be used to establish precedent in another cases, I'm sure.
A short barreled rifle is defined in the US Code, Title 18, Part I, Chapter, Sec. 921. as follows...
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
(8) The term ''short-barreled rifle'' means a rifle having one or more barrels less than sixteen inches in length and any weapon made from a rifle (whether by alteration, modification, or otherwise) if such weapon, as modified, has an overall length of less than twenty-six inches.
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
The ATF agrues in these cases about the ease at which the modification can be made. Not black and white for sure where the line between easy and hard is I grant you, and the ATF will never define or tell the public what that line is. The ATFs testimony was centered on the ease and speed in which the complete gun could be assembled. It can be argued that without the proper tools, a separate barrel can not be assembled into a working SBR in a timely fashion and is actually just a part. I probably went overbored in my other post. My point is to answer and make recommendations to NFA questions with facts, court cases, etc., not scare tactics. The link provided may apply here but it is not the exact situation as the OP is asking about a barrel not a complete upper. Wonder if the Thompson Contender case would of had any bearing on the outcome had it been used or applicable.