I know I've seen youtubes with non-leo/non-military folks shooting chain guns. I don't believe those existed before 1986, did they? May be a money talks thing.
Has nothing to do with "money talks"......I have shot lots of machine guns that were built after '86, but they are not transferrable and I can't own them. I have friends that hold NFA dealer (SOT) or manufacturer licenses and they can legally possess/own post '86 machine guns under certain circumstances. These guns are known as "post '86 dealer samples".
https://www.atf.gov/firearms/docs/atf-national-firearms-act-handbook-chapter-7/download