Dimitrios Karras of Ares Armor noticed some discrepancies concerning the BATFE release of ATF Rul. 2015-1, specifically, their inconsistencies in ruling what exactly construes a receiver, a weapon, and the manufacture thereof.
Karras states the issue with a formal letter to B. Todd Jones, Director of the Bureau of Alcohol, Tobacco, Firearms, and Explosives:
Click to access B.Todd%20Letter%20re%20Ruling.pdf
Given the problems with BATFE personnel understanding the technical and legal ramifications of their ruling, Karras provides a coloring book version describing the issue in crayon.