if you want to register AR as AW, then you have to own it before 2017 1/1, otherwise it does not matter. you can buy lower now if you want and can find one available, or next year, and then buy other parts to assemble a featureless AR.
1. 单独lower是枪但不是AW(终极featureless,都不能打),没有注册的资格
2. 看过去注册的表格,我估计表格上至少还会让你填写barrel length等特征,并且签名处还会有“i declare under penalty of perjury that the information provided is correct之类的表达。
3. 明年1月1号开始制造AW(组装非featureless的AR)是 felony。
4. 政府要证明你违法难度较高,但是一旦有证据(比如说你自己经受不住压力和警察坦白,或者找到了你的upper的购买记录甚至只是这个帖子),我认为陪审团有较大的概率给你定罪。