In a manner of speaking, your retired friend was correct.
Federal laws do in fact control firearms & their sale, manufacture, possession etc.
You could not sit in your house or tool shed and build full auto machine guns then sell them to North Korea or Iran.
The federal LE agencies like ATF, FBI, IRS, US Postal Inspectors, etc would be all over you.
James Yeager, the brash Youtuber & gun class instructor made a short video claiming the end of Prohibition(sale of alcoholic beverages) led to the Volclure/McClure Act which reduced ownership & use of automatic weapons. Yeager stated this action was intended to give the federal LE agents new duties and jobs.
I highly doubt any political actions or plots were that contrived.