I can't answer your question authoritatively, but I'd guess "yes" in that AR Pistol probably qualifies (although the pure ATF definition may not precisely cover it) as an SBR, and about all you really can worry about is the straight-wall case. (Qualifies as a pistol, too
I'm sure we've got somebody here who can give you a definitive statement. When I thought about it (I'm not a hunter), it seemed like my full-sized 1911's would "fit", but I think there was a zinger in there somemplace. My Officer's sized 1911 wouldn't make it on the barrel length...
There's a sticky at http://forums.buckeyefirearms.org/viewtopic.php?f=6&t=10097
that you should have a look at, but it's not mandatory, and may be sleep inducing. No need to go past the first couple pages....