what kind of kinetic mechanical interaction is the explosion made in a gun to shoot out a bullet?

Answer 1

The definition of explosion is that the chemical reaction is proceeding across the material being consumed faster than the speed of sound in the material. The thing that makes the bullet go out the barrel is an extreme pressure differential between the back of the projectile and the front of the projectile. The rapid burning of the powder in the bullet ensures that the pressure behind the bullet remains higher than the front of the projectile even when the projectile is moving very fast down the barrel.