yeah i think they illegal now, even though ive seen guys at gun shows selling them, and with all the DOJ agents walking i wonder how they get away with it.
those things arent really worth it since bump fire does the exact same thing in prolly the same way.
IF they were legal and you IF you found one that was worth a damn then it might be cool for a 22 rifle, but ferget it with any other centerfire semi auto.
one thing to HIGHLY consider is that with bump firing and trigger devices ....they bring UNWANTED ATTENTION.
they work toooo good and everyone who doesnt know its bump firing thinks its full auto. so your range might have a hissy fit or if your on private land or way out in the desert the cops could be called. then you gotta prove its a semi auto gun and explain what your doing.