I do plan on SBR pistol to make it legal, but carbine does not need to be registered, so the question is being able to turn your SBR into a carbine legal? Also the original question was, Does CZ even sell the different barrel lengths and can you even swap them out,(do the thread on or are they pinned?). If CZ does not even sell the barrels then what I am wanting to do is a moot point. Thanks for any info you might have.