some guy on a different board said it was legal for flash hider on post ban....how come they don't normally come on rifles then?  i'm guessing he was wrong?...

Yes, he was wrong.  You can have a muzzle brake, but not a flash hider on a postban.

thats what i thought...just checking to see if i missed something on that.  

It's a question of terminology.  There is a difference between a flash 'hider' and a flash 'suppressor'.

Flash suppressors are forbidden on post-ban semi-autos with a detachable magazine and a pistol grip.

Flash hiders (which do not suppress flash) are not forbidden.

A flash hider like the old-style M1 carbine conical flash hiders do not suppress flash - merely shield the shooter's eyes from the worst effects of the muzzle blast.  They are not prohibited if they don't suppress muzzle flash.

Oh, c'mon now Circuits; you think a "flash hider" would not be ruled by BATF to be the same (for purposes of 922(v)) as a "flash supressor"?  Consider a sound supressor; they are considered flash supressors even though they merely hide the flash from view.  Also consider the early M16 flash supressors which were ruled to be sound supressors requiring registration when in private hands because they had the collateral effect of a mere 1-2dB reduction of sound.  

Well, shaggy - you gotta take what you can, given the wording of the law.

I do think a conical flash hider could not be shown to be a flash suppressor, since any objective measurement would show similar muzzle signatures.  If a brake or compensator can pass muster as not being a flash suppressor, then a conical flash hider certainly could.

I don't see much demand for them, though - it just doesn't look right on an AR.  It might have some limited application for low-light shooting, if available in a clamp-on version not requiring muzzle threads.