In my world, which may or may not be your world, BR=Blu-Ray.
Because...
Digital Video/Versatile Disc => DVD, but do folks say Digital Video/Versatile Disc? No. And I hope no one obnoxious chimes in and says they do.
Blu Ray Disc => BRD, but does anyone say Blu Ray Disc? No, folks say Blu-Ray.
Blu Ray => BR