Good evening everyone. The purpose of this thread is to determine the legality of the MechTech Carbine Conversion Unit (CCU) with regard to NFA regulations. http://mechtechsys.com/images/web/GlockCCU_full.jpg I became interested in this accessory after my search for a Keltec Sub2000 came up empty. The CCU looks solid but it is not without its share of caveats. So far, my research has led me to several forums with members arguing opposing points of view. The consensus is that using this device to convert a glock to a rifle/carbine is perfectly legal but taking it off and putting your glock slide and barrel back on constitutes 'creating' a new firearm out of what is now a rifle. Anyone who understands how this device works can see that there is absolutely no way to use it to create an SBR or AOW out of your glock without modifying the glock, the CCU or both. Misinterpretation of the law can often mean the difference between fun at the range and a knock on your door from the BATFE; something I'd rather avoid. The BATFE has made a recent revision to their NFA rule book. http://www.atf.gov/regulations-rulings/rulings/atf-rulings/atf-ruling-2011-4.pdf I think I understand what they are trying to say but for those of us who did not go to law school, we are often left to interpret these laws at our own risk. My interpretation of this ruling is; Once a rifle, always a rifle/Once a pistol, always a pistol. And as long as the kit/device/accessory does not result in the creation of (or the ability to create) an NFA weapon, you are in the clear. So by taking the CCU off your glock, you are NOT making a new weapon out of a rifle and you are NOT making an NFA regulated weapon. Is this a correct interpretation?