Why wouldn't you be able to? As long as it doesn't say "flash hider" on the package lmao... then again because BATFE doesnt test devices anymore this is a dead issue at that
level. MGL doesn't have a spec for a "flash hider" either. .... so good luck with that.
But if you are talking stuff like Levang linear comps, or that thing that surefire makes (Warden) etc, I can't see how those would ever be illegal on any AR.
If you're talking REAL preban, it wouldnt matter anyways (pre 9/13/94). Not "pre healyban" which is not really a "thing" as far as I'm concerned.