I was chatting with another member on here when we met up for a trade and the topic of SBR came up.* Why are SBR, for example an AR15, classified as a NFA item that needs to be registered?* I am not venting but I just don't understand how I can legally own an ar15 pistol, granted it's under the 26", and i can legally own an ar15 rifle?* Neither one of these are required to be registered w/ the ATF as an NFA item. But if i were to take the upper off of the pistol and attach it to a (non pistol designated) lower it's now required to be registered and the taxed? I understand full auto weapons and surpressors needing to be registered and regulated. However a combination of 2 non nfa weapons is then regulated by the ATF? I am really curious about the logic behind this example. I imagined it cannot be because of concealment issues since the pistol ar15 is much easier to conceal. Any explanations?