Rythym nailed it, doesn't matter if it's a dumb-ass and dangerous alteration or a true swap of the bolt carrier to actuate the sear when the select lever is in the auto/burst position. What matters is doing either without an FFL is fuck-all illegal. I'd like to think the bad apples can't spoil it for the rest of us, but stereotyping is big these days.
Creationists are like Slinkys: It's hard not to giggle when they tumble down the stairs.