I've successfully driven tacks with Muzzy's in upper 290's....Honestly with a quality tuned bow/matched arrow combo, I doubt you couldn't tune most fixed blade heads to do the same, if there is a speed at which you can no longer tune fix blade heads, I don't know what that speed is. If your shop cannot do that, they are pushing mechanicals and either don't know how or want to put the time in to do it.....