The ATF needs a serious overhaul. Their "determinations" are often backwards, confusing, conflicting and unnecessary. They recently released that they will be making some formal statement of some sort regarding the angle of a fore grip and whether modular silencers are legal.
https://blog.princelaw.com/2017/08/03/breaking-news-atf-to-issue-two-monumental-determinations/
https://blog.princelaw.com/2017/08/03/breaking-news-atf-to-issue-two-monumental-determinations/