The ATF says that almost all pistol-braced firearms are SBR's. MSP says that they're pistols and NOT considered SBR's by MSP. I believe there is an injunction in a district court against the ATF's "final rule" but I haven't kept up to date on that, so I'm not aware of whether that applies to everyone or not. I'm also fairly certain that this model is on the handgun roster, so you shouldn't have any trouble transferring it in Maryland. Blue Fins has always been fine about stuff like that in my experience. I doubt they would transfer you an item that's a felony to possess.