Bullets shooting through wall

Dear BF Community,

Okay I'm kind of angry now because I just got out from a Breakthrough game 2 minutes ago, there was a player with 208 kills and 0 death in Columbia Heights, he had 78 kills in just sector 1 alone.

Also, the player's M240L bullets can shoot through walls and headshot everytime he hits.

Is there a bullet type that allows players to shoot through wall?