http://www.youtube.com/watch?v=FOlMyO_qe8o&feature=youtu.be
http://www.youtube.com/watch?v=Ho0StB6FPys&feature=youtu.be
It seems that where you aim, if too low, even though you can both see your target through scopes/sights + you can see your gun is actually hanging off the edge, you end up shooting your cover.
Second video I also clipped through the tower.