I question the usefulness of these, given that if you are able to use them, you've done something terribly wrong. But, the real question: How long before the anti-gun side adds them to the list of cosmetic accessories that defines an 'assault weapon'?
I've got one AR rifle with a Yankee Hill flash hider with a serrated edge on it---for me, it's mainly for looks, but might come in handy prodding prisoners or breaking glass. Those other two do-dads would be un-needed weight to carry around. I try to keep my rifles as light as necessary. The lighter the gun, the faster you can move it around and fire it.
Of course they're going to hate it, since it's really just another form of bayonet. It's a good thing they saved us from all these bayonet attacks, we can sleep easier at night now.
Yeah lot of grey area there with regards to ATF and DD's. Personally I don't see the value of a launcher, since the problem is the ammo itself. Even if you do everything legally, it's still nearly impossible to get the grenades because no one will want to sell you any from what I've read. If you somehow manage to procure the grenades, do you really want those things sitting around? They're useless when it comes to self defense. If I start needing grenades I've got worse problems. If I need to launch flares I'll just get a perfectly legal flare gun.
No one can cite a single instance where a live grenade launcher was used in a crime - the left added them to the ban because of a perceived threat that has no basis in reality. You know - par for the course.
For the purpose of the AWB, a grenade launcher attachment is just something on the barrel, like a bayonet lug. It's used for the old-fashioned rifle grenades. This pic shows a rifle grenade. https://en.wikipedia.org/wiki/File:M1_Garand_rifgren-shooting_line.jpg