C4 explosives are designed to be impact-resistant and can't be set off by gunfire.
When Butch and Selina arrive at the Pikes (firebugs) home, it is the exact same house as Cranes house in season 1 (The Scarecrow) where he sees his burning wife on the steps.
When the scene where James Gordon, and Harvey Bullock chase Evan Pike into a dead end and blow him up. You can see the wire from the explosives running all the way behind the camera.