Oleg, when shotgun pellets (and most bullets) strike a solid object (like a concrete wall) at an angle, they tend to follow the surface of that object very closely.
In other words if they impact the wall at 30 degrees, they will bounce off at a much more shallow angle.
If a "scroat" is shooting around a corner of a building using good cover, it's better to shoot closer to his "protected" side than center of exposed mass.
Not only do bullets skip, they tend to send all sorts of nasty fragments of building material and bullet particles, (jacket/core/etc.), that make it hard for a "perp" to see you (or anything else ever again)!
This rule holds true for both horizontal and vertical surfaces. It's better to error on the side of a hard surface than sending your projectiles into thin air!
Regards! DaMan
[This message has been edited by DaMan (edited August 16, 2000).]