As others have noted, 80 mins for a connection is a non-starter.
Assuming you are connecting to AA, you would:
-Deplane from BA and walk to a mobile lounge (as a regular traveller in and out of IAD, this, to me, is the worst experience of traversing the airport);
-Get squashed into said mobile lounge;
-Mobile lounge takes you to IAB (International Arrivals Building) for immigration and customs;
-After immigration go to carousel and wait for bag (if you checked one);
-Take bag through customs;
-Exit arrivals hall and go upstairs in main terminal;
-Re-check bags upstairs with AA;
-Go through security again and walk or take Aerotrain to B gates for AA departure.
There's a much more sardonic version of the arrival process in this trip report
http://www.flyertalk.com/forum/trip-...d-back-ba.html