Originally Posted by
Toonces
i would be very careful with this, as this is likely committing a felony.
Per the BATFE, putting a long barrel on an AR or SBS removes the "short" part of the equation, returning them to normal status. Taking the stock off an AR or SBS wouldn't, as they have been registered as long guns.
The BATFE has ruled in the past that "once a rifle, always a rifle". For example, you can register an XP-100 as an SBR. But you can't take a Model 7 or 700, and remove the shoulder stock/chop the barrel to make a pistol. To treat the XP-100 SBR as normal, you would have to install a 16"+ barrel. The same would go for that revolver, if it has been registered as a SBR.