Rick Vasquez is the retired ATF expert witness that was supposed to testify that a bumpstock is not a machine gun and that the charge is bogus. He was the one that made the initial decision that they weren't machine guns in the first place.
He was in the Marine Corps for 21 years and was an advanced gunsmith and armorer in Quantico. Then he worked as an armorer and gunsmith for US Dept of State then went to ATF Firearms Technology Branch (the guys that make determinations about firearms).
https://www.rickvasquezfirearms.com/about-rickI don't know if he's on "our side" but he made the determination based on facts, tech specs, and the letter of the law - LIKE THEY'RE SUPPOSED TO DO!
https://www.thetrace.org/rounds/atf-bump-stock-evaluation-legal-machine-gun/ - "ATF Official Who Evaluated the Bump Stock’s Legality Pushes Back Against Critics"
Vice news also interviewed him after the Mandalay Bay shooting and he continued to stand by their determination that a bumpstock is NOT a machinegun . One trigger pull, one round. Common sense, despite what NRA, Trump, Paul Ryan and others said. See interview at 3:00
https://youtu.be/2_A-B8hlrTs?t=180In his interview with MAC, he says what we all know that making arbitrary regulations like this (NOT LAW) is crazy and dangerous.
https://www.youtube.com/watch?v=JYMRzLaRU_o He also talks about how and why the Q Honey Badger got stomped on
https://www.tactical-life.com/news/atf-targets-q-honey-badger/