Here is the result of a "What's the Call?" thread on the SASS Wire:
For shots that ricochet off something (e.g., the ground or a target) before hitting a second thing, it is the first impact that counts. For example:
If the instructions are to sweep five pistol targets from left (P1, P2, P3, P4, P5) ...
1) If shooter's first shot hits P2 and ricochets and hits P1, it is a Procedural (follow the Miss Flow Chart)
2) If the shooter's first shot hits P1 and ricochets and hits R6 (rifle target), it is a hit
3) If the shooter's first shot hits the ground in front of P1 and then ricochets up to hit P1, it is a miss.
On shotgun targets that fall after an apparent impact in front of the target, one would be hard pressed to know if the target was hit by shot or by a ricochet, so the benefit of the doubt goes to the shooter.
Reference: Post #93 on this thread:
http://sassnet.com/forums/index.php?s=10a072d880833d631a05078a3352ab86&showtopic=245046&page=3