chung wrote:
As the title asks, I bought a factory sbr in 300 blk. Does anyone know if I can sell the upper and keep the factory lower and remain in good legal standing to use it as a sbr with other uppers? Or do I need to keep the original factory upper around that I bought it with.
What Madpick said.
The key to compliance is not retaining the exact original barreled upper assembly itself, but rather being able to restore the SBR to its original configuration (registered length & caliber). Or, if you wish to change those attributes, notifying the ATF in writing.
Just make sure that none of the NFA compliance markings are on the upper that you wish to sell (it's not common, but it's possible).