Hey guys im going to start my third build soon. I would really like to do a 11.5" build the, question i have is how do go about doing the build legally. Im prepared to pay the 200 tax stamp for sbr. What i wanna do is start out with a pistol then pay the tax to put the stock on it. I have stripped lowers i would like to use, but read that the lower needs to be a pistol lower. Do i specifically have to buy a pistol lower?