The empty places of stairway impossible to shoot through.
BIS please watch video: http://www.youtube.com/watch?v=SKRWAB2CU-A&feature=youtu.be

I'm not sure all stairway in the game have this problem or not.
This stairway is located on the Altis Factory.
The Collision model of stairway in the game should be checked.
Probably many stairway or even all have this problem. This in not normal...