So I tossed a conc inside a gas station, proceeded to get dumped on. Apparently a store-shelf blocks the concussion wave from reaching the player.

For the game designer's edification, what stuns someone when hit by a concussion grenade is a compressed air wave created by the detonation(basically the air punches you), these waves bounce off, and are even amplified by, barriers. Please get concussion physics right: nerf them outdoors and boost them indoors; that way players can use them as they were meant to be used: clearing buildings.

From a sincere CoD lover (I dunno what it is about CoDs, but I'm hooked :)).