Large vehicles with turrets do not respect dimensions of object that they are passing through.
End of weapon barrel appears to not affect geometry, and when facing front or rear with vehicle
When end of weapon barrel is left or right 90 degrees off center, collisions can occur with buildings.

Videos
http://youtu.be/U--k0bNXQJ8 (Blocked Entry)

http://youtu.be/iDDvPGla6JM (Large Turret passes though roof/walls)
http://youtu.be/FNlXtSe7gf8 (Large Turret passes though roof/walls)
http://youtu.be/oMUbWrWOB-M (Large Turret passes though roof/walls)